Nuova Elettronica Handbook For The New Paradigm 4,6/5 6913votes
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$5 becomes $20! Dear Internet Archive Supporter, I ask only once a year: please help the Internet Archive today. We’re an independent, non-profit website that the entire world depends on. Our work is powered by donations averaging about $41. If everyone chips in $5, we can keep this going for free.
For the cost of a used paperback, we can share a book online forever. When I started this, people called me crazy.
Collect web pages? Who’d want to read a book on a screen? For 21 years, we’ve backed up the Web, so if government data or entire newspapers disappear, we can say: We Got This. We’re dedicated to reader privacy. We never accept ads.
But we still need to pay for servers and staff. If you find our site useful, please chip in. —Brewster Kahle, Founder, Internet Archive. Donor challenge: A generous supporter will match your donation 3 to 1 right now. $5 becomes $20!
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Free Download Pokemon White 2 Nds Rom English. When I started this, people called me crazy. Collect web pages? Who’d want to read a book on a screen?
For 21 years, we’ve backed up the Web, so if government data or entire newspapers disappear, we can say: We Got This. We’re dedicated to reader privacy. We never accept ads.
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We’re an independent, non-profit website that the entire world depends on. Our work is powered by donations averaging about $41. If everyone chips in $5, we can keep this going for free. For the cost of a used paperback, we can share a book online forever.
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• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Measuring and testing • - modern measurement instruments can be networked using corporate lan, but before you can connect, you must work with your network administrator • - document in pdf format • • - DSP techniques lead to faster, less costly frequency-response tests and enable the use of a powerful concept, the coherence function, which acts as a watchdog to help identify and quantify common but easy-to-miss measurement errors. Best of all, this watchdog works for free. • - are the ABCs of this huge class of instruments • - Bridge-type, piezoelectric, and other sensors are subject to nonlinearities, as well as gain and offset errors. Smart signal conditioners compensate for the errors and extract the true signals from the dross. Pressure transducers, accelerometers, temperature sensors, and linear-position sensors are often imperfect devices, prone to nonlinearities and gain and offset errors. • • - Aliasing, long considered an undesirable artifact of an insufficiently high sampling rate, is in fact a useful tool for lab testing and analysis. • - A meter is a measuring instrument.
An ammeter measures current, a voltmeter measures the potential difference (voltage) between two points, and an ohmmeter measures resistance. A multimeter combines these functions, and possibly some additional ones as well, into a single instrument. • - A very handy tool for trouble shooting problems is a VOM (Volt Ohm Meter) - also called a Multi-Meter. It can be used to test cables, AC power levels and Batteries.
You'll often find yourself out on the road with problems that are causing you grief, but you aren't quite sure why. • - The decibel (dB) is a logarithmic unit used to describe a ratio.
The ratio may be power, or voltage or intensity or several other things. IEEE 488 is propably the mostly adopted communication bus and protocol used in electronic measusing equioment. In 1977, the IEEE adopted the bus structure and communication protocol that it named IEEE 488.
Some others call it GPIB (general-purpose instrumentation bus). The bus's original name was HPIB (Hewlett-Packard instrumentation bus). Until the advent of the HPIB, no standardized methods existed for interfacing instruments with computers. IEEE 488 remained for more than two decades the industry's primary standard for enabling instruments and computers to talk with one another.IEEE 488 standard did a good job of defining the communications hardware, it initially gave short shrift to interfacing's software aspects. More than a decade elapsed before the evolution of the necessary software standards, particularly SCPI (standard commands for programmable instruments).IEEE 488 was not the only interface used. RS-232 ports have became popular on slower instruments.
The two top contenders for the instrument-interfacing standard of the future are Ethernet and USB. You can find one or both in many instruments. Scopes that offer communication ports other than IEEE 488 are becoming increasingly common. The current and most likely future leader in replacing IEEE 488 is Ethernet.
USB will also play a major role. The most obvious reasons for turning to computer-standard interfaces in place of IEEE 488 for instruments are cost, size, cable length of instrument networks, and increasing difficulty of installing specialized peripheral controllers in newer PCs. For test instruments, an advantage of an Ethernet connection over a USB or IEEE 488 connection is Ethernet's much greater allowable cable length.
Ethernet LANs.even using gigabit-per-second Ethernet technology.can span thousands of feet. USB and IEEE 488 are limited to tens of feet. Don't be fooled by the new protocols' high nominal bit rates; instrument interfacing usually involves short messages. In such service, IEEE 488 can be significantly faster than protocols that at first appear to be much faster than IEEE 488.Using an instrument as a Web server is a new aspect in interfacing. Web-server technology is particularly well-suited to instruments that connect to Ethernet networks and that use TCP/IP (Transfer Control Protocol/Internet Protocol).
• - Nothing good lasts forever, but IEEE 488's slow decline is making the venerable instrument-interface standard seem immortal. Every scientist, engineer, and technician involved in any form of electronics has used an oscilloscope. Scope displays of amplitude as a function of time provide intuitive and easily interpreted pictures of signals.
Oscilloscope is one of the most important test instruments foravailable engineers. It is useful for very many electronics measurement. The main purpose of an oscilloscope is to display the level of a signal relative to changes in time. You can use an oscilloscope to analyze signal waveform, get some idea of signal frequency and many other details.Scopes are ment for looking at the qualitative aspects of the signal (like signal waveform, esitence of signal, etc.). For making quantitative measurements, a scope is 'usually' a bad choice (for example multimeter is more accurate tool to measure DC voltage levels than a scope). It is quite typical for the scope to be out by a percent or two or three but if you're counting on that kind of accuracy, you're using the wrong tool.
Deviations as high as ~3% or more are considered 'in-cal', and in uncalibrated scopes this can be much worse. Traditional oscilloscopes used a CRT screen and were completely analogue devices.
Those analogue oscilloscopes are still very usable devicesnowadays. Analogue oscilloscopes work very well as general testing instrumentfor viewing repetitive signals. Many simple and cheap analogue oscilloscopes have typical bandwidth of 20 MHz. Some better ones go to 100 Mhz or higher in bandwidth. Even a 20MHz analogue scope will produce some response at a higher frequency but of course it will be at a lower level because it is outside of the calibrated specified bandwidth. Digital oscilloscopes are digital versions of that analogue instruments. Digital oscilloscopes sample signals using a fast analog-to-digital converter (ADC).
The digitized signals aresotred to the scope memory and shown on the scope screen or at computer screen. The benefit of the digital technology is thatthe waveforms can be captured to memory and then analyzed, immediatlyor later, in many ways. Digital oscilloscopes can be used to capturerepetitive signals as well as transient signals. Oscilloscope bandwidth is generally listed as the -3-dB point in oscilloscope frequency response. Traditionally, oscilloscopes have exhibited a Gaussian frequency response. A Gaussian response results from the scope design's combining many circuit elements that have similar frequency responses. Analog oscilloscopes achieve their frequency response in this manner, thanks to chains of amplifiers from the input BNCs to the CRT display.
(Analog oscilloscopes used the input signal to directly deflect the electron beam in a CRT. This architecture required amplifying the input signal by three orders of magnitude and driving the large capacitive load that the CRT deflection plates presented.) The properties of Gaussian-response oscilloscopes are fairly well-taught and well-understood throughout the industry.
In a Gaussian-response oscilloscope, the oscilloscope's rise time is related to the oscilloscope's bandwidth by the familiar and commonly used formula, rise time=0.35/bandwidth. (Rise time is measured from the pulse's 10 to 90% amplitude points. Bandwidth is defined as the frequency at which the response is down 3 dB relative to dc.
The theoretical relationship for a Gaussian system is rise time=0.339/bandwidth, but the industry has settled on 0.35/bandwidth as a practical formula.) Another commonly used property of Gaussian systems is the overall system bandwidth, which is the rms value of the individual bandwidths. You can calculate it using the familiar relationship, system bandwidth=1/(1/BWPROBE2+1/BWOSCILLOSCOPE2)0.5. 'System bandwidth' refers to the bandwidth you achieve with a combination of an oscilloscope probe and oscilloscope. Oscilloscope probes are often designed to have sufficiently higher bandwidth than the oscilloscope bandwidth, so that the above formula is usually not necessary. Most oscilloscopes are built so that the signal input connector is BNC connector. The input impedance in the connetion is typically around 1 megaohm in typical normal oscilloscopes and 50 ohms in many high speed oscilloscopes (check what you have from scope manual).
The connector ground side (outer shield) is normally connected to the equipment case ground which is generally wired to mains ground through mains connector. This means that the grounds of all channels are genrally connected together and then wired to mains ground (unless you power your scope through safety isolation transformer which isolated your scope from ground). Oscilloscopes are intended to be operated with their chassis at ground potntial. There are good technical and safety resons for this. If you are measuring some mains powered device, it is a very good idea to power the device through an isolation transformer. When working with mains powered equipment, the equipment you measure should be isolated from mains voltage for safety reasons.
When doing the meausrement the right grounding is important for meaningful results. A good oscilloscope probe has a removeable ground lead, that allows the user to ground it to circuit board or not depending on what is needed in that specific meaurement. In general case the measurements are made better and more accurate with the ground lead connected. If you do not connect the ground lead then the display will show allthe noise the probe cable picks up (cable acts like antenna that picks up noise nearby). If you want rid of this you connect the ground lead to the low of the circuit you are trying to monitor.
The oscilloscope ground lead will eventually find its way back to the mains earth of the oscilloscope.If you are trying to make measurements, you must have a reference against which to measure. Without that, 'Pissing against the wind' comes to mind, as acomparison. There are some potential dangers when the circuit ground is at a potential with respect to oscilloscope ground then current will flow in the oscilloscope through the measuring cable shield.
If the potential on the circuit is direction connection to mains then there will be a bang and possibly some damaged measuring hardware / circuit. Remedies are: • a) Double insulated oscilloscopes with no ground connection • b) Battery powered osciloscopes • c) Differential input oscilloscopes • d) Differential input adapter for your oscilloscope • e) Isolating transformers Using the option e is by far the cheapest and most commonly used, although not always the best. There are also some special oscilloscopes (expensive ones) with inputs that are not connected to ground (usually referred as differential inputs). This kind of scope can be safely connected to almost any electronics circuit. You can get the same performance with a normal scope also if you use a differential proble connected to a normal oscilloscope. In some cases the battery powered small oscilloscopes are very handly because those devices are completely floating.
If you want to make accurate measurements, you need to have your oscilloscope calibrated. A calibrated scope will allow you to make considerably more accuratetime/voltage measurements, will show square waves as true step-functions(even at the highest sweep rates) and not some sort of distortedrepresentation, and most importantly it will trigger reliably on signals.There's a whole lot of difference between a calibrated and un-calibratedscope, but you wouldn't usually know it unless you have a source of precision calibration signals to compare against. Once calibrated, an instrument should be re-calibrated within 2-3 years since the adjustments can in fact vary a surprising amount over time (the time interval could vary somewhat depending on scope type and needed calibration accuracy). A scope requires significantly more maintenance than simpler measurement instruments like a multi-meter or signal generator.
CRT based oscilloscopes are complex instruments. Much more complex than almost any other piece of test instrumentation and the circuitry is not selfadjusting (for the most part).
Most common analog oscilloscopes require a fair amount of specialty calibration equipment and a thorough calibrationtakes at least 1/2 day and often longer (there can be up to 50 separate adjustments tha can be made on older scope, this is labor intensive process to get them right). Most scope problems are revealed in the calibrationprocedure in which the tech can choose to either ignore or repair. Sometimes the repairs are trivial, sometimes not. Becauses the cost of maintaining older oscilloscopes accurately many so-called 'working' units find themselves on the surplus market.
The oscilloscope probe used to establish a connection between the circuit under test and the measuring instrument. A probe can be any conductor used to establish a connection between the circuit under test and the measuring instrument. This conductor could be a piece of bare wire, a multimeter lead or a piece of unterminated coaxial cable.
These 'simple probes,' however, do not fulfill the essential purpose of a probe; that is, 'to extract minimal energy from the circuit under test and transfer it to a measuring instrument with maximum fidelity.' There are many different kinds of probes that suit to different applications: • The bare wire can load the input amplifier with its high capacitance and inductance or even cause a short circuit; multimeter leads are unshielded and are often susceptible to stray pickup • The unterminated coax will severely capacitively load the circuit under test (100 pF per meter typically). Also, the unterminated coax is usually resonant at certain frequencies and does not allow faithful transfer of the signal to the test instrument due to reflections.
• A simplest probe type is is 'x1' probe that just consists of probe tip, grounding conductor and low capacitance coaxial cable to the oscilloscope. Typically the oscilloscope at probe setting 'x1' it loads the circuit being measured with the full capacitance of probe + probe cable + oscilloscope input. The unterminated coax will severely capacitively load the circuit under test. Typical capacitance of 'x1' probe is tens of picofarads. For DC measurements the input resistance is the same the resistance of the oscilloscope input (typically 1 Mohm on traditional CRO-type oscilloscopes, 50 ohm on some high frequency models). • Attenuating Passive Voltage Probes are the most commonly used probes today.
The 'x10' setting gives you reduced sensitivity and reduced capacitace (the load capacitance is around one tenth of 'x1' setting). This means a typical input capacitance of around 15-20 pF. The 10X passive voltage probe presents a high impedance to the circuit under test at low frequencies (approximately 5 MHz and lower).
Their main disadvantage is a decreasing impedance level with increasing frequency (i.e., high input capacitance). • FET probes include active components (field effect transistors or other active devices) rather than passive components. The FET input results in a higher input impedance without loss of signal, i.e., low input capacitance (typically less than 1 pF) and high input resistance values (typically higher than 20 kohms).
Since FET probes have a 50 ohm output impedance, they can drive a 50? Cable so they can be long cables between the probe and oscilloscope.
Downside of FET probes are that they are typically expensive and need operating power to work (either supplied by oscilloscope using properietary methods or powered with batteries). • Several high voltage probes are available, and they typically provide 100X or 1000X compensated dividers.
Because of the larger attenuation factors required for high voltage applications, the input capacitance is typically reduced to approximately 3 pF. • 50 ohm Divider Probes provide the lowest input capacitance (typically less than 1 pF for high frequency signals) and are used with high frequency, 50 ohm input scopes. The simplest 50 ohm divider probe consists of just one 1 kohm or 2.2 kohm resistor that is placed between the signal connection on the circuit and the 50 ohm ciaxial cable going to the oscilloscope. • Current probes provide a method to measure the current flowing in a circuit. Two types of current probes are available, the traditional AC only probes and the 'Hall Effect' semiconductor type. AC only current probes use a transformer to convert current flux into AC signals. Combining a 'Hall Effect' device with an AC transformer provides a frequency response from DC up to many MHz range.
Because of its 'non-invasive' nature, a current probe typically imposes less loading than other probe types. The AC current probes can be just passive devices, while the models with 'Hall Effect' device need some operating power (typically provided by local battery on the probe). • Proper probe selection will extend and enhance an instrument's performance, while imprudent probe selection often reduces your system's performance. When making measurements make sure not to exceed the maximum allowable input ratings of the oscilloscope input ports. This will prevent costly damage and provide reliable measurements. Rememeber also not to exceed the input voltage ratigns of oscilloscope probes as well, because this can damage the probes and cause severe safety risk to the person using those probes.
A proper oscilloscope probe grounding is essential requirement to get meaningful measuring results with normal oscilloscope probes. The measured the current must always form a loop. The signal beign measured cannot exit the measured circuit and go to the oscilloscope input without having a path through which it may return.
If you are measuring a 'floating' circuit, then the return would go through a parasitic capacitance directly between the oscillator and the scope. This capacitance varies depending how the devices are positiones, which means that the position of the probe cable will have an effect on the shape of the signals you see on the scope! Another nasty artifact of a no-ground probe arrangement is the resonance associated with the combination of the rather large inductance of cable, and the input capacitance of the probe.
This resonance is called a probe resonance and can cause considerable measurement errors. A short, explicit ground connection made between the scope ground and the equipment under test shunts those capacitances and inductances, eliminating their influence on the measured result and pushing the probe resonance up and out of the band of interest. All good probes come with short, tiny ground attachments to prevent such problems. For single-ended measurements, don't depend on mysterious ground connections.
Always use a good, short ground connection. Oscilloscopes are used for very many different kind of measurements.
In telecommunication and data communications applications you can often see results of eye diagram and eye pattern measurement. An eye pattern is an oscilloscope display in which a pseudorandom digital data signal from a receiver is repetitively sampled and applied to the vertical input, while the data rate is used to trigger the horizontal sweep. System performance information can be derived by analyzing the display.
An open eye pattern corresponds to minimal signal distortion. Distortion of the signal waveform due to intersymbol interference and noise appears as closure of the eye pattern. Many modern digital oscilloscopes allow you to show you signal waveforms and even store the recorded signal for later inspection. Old analogue oscilloscopes lacked the ability to store the picture on the screen, unless you took a picture of the screen with a normal film camera (not very convient, camera settings needs to be right). If you happen to have an old analogue oscilloscope and need to store the waveform on the screen, then you might be able to use modern inexpensive digital camera connected to computer instead of old traditional film camera. You can for example have an usb pc camera mounted on a tripod at the?oscilloscope screen, focus close for a sharp picture,?camera output cable into the USB port.
With the bundled software installed on your computer (Windows 98se, 2000, or never), you can view the image on your computer screen and save the image on the oscilloscope screen to you hard disk (for example to be included to your laboratory documents later). You see it all in real time (well almost.) and if you are recording it all as well, then you have the option of playback, editing and splicing the info/displays later for whatever purpose?or archiving etc.?It work, usually well. This could be an useful trick for those technicians out there with limited funds and equipment. Digital cameras and webcams are nowadays quite cheap compared to a modern digital oscilloscope.
Articles • • - Video signals are complex waveforms comprised of signals representing a picture as well as the timing information needed to display the picture. To capture and measure these complex signals, you need powerful instruments tailored for this application. But, because of the variety of video standards, you also need a general-purpose instrument that can provide accurate information - quickly and easily. • - This technical note focuses on the uses of digital scopes for measuring power supply characteristics.
Examples are given of measuring power supply turn-on, hold-up time when AC power fails, in rush current and ripple/noise. • - information on those scopes and some general scope tips • - Oscilloscopes' single-ended inputs present challenges when you try to view signals that are not referenced to ground.
Some work-arounds not only can mislead, but also can kill. True differential measurements are safe and accurate, however. • - if you don't appreciate the complex operations that produce them, the displays can mislead you, resulting in costly errors in buying scopes • • from • - This set of technical notes discusses the application of digital oscilloscopes to a variety of problems encountered in communications.
Examples are given of how to use the benefits of a DSO in examining phase shift keying, frequency shift keying, full duplex, etc. • - with color and intensity gradients, the displays in new digital scopes nearly emulate those of analog models • - All digital systems are concerned with adequate timing margins. As clock speeds in communications and semiconductors continue to increase, timing margins get even narrower. As clock frequencies increase, a parameter that has even greater impact on measurement needs is edge speed.
• - A scope probe is built to minimize ringing by adding resistance. A X10 probe has the effect of reducing capacitance by a factor of ten. The trade-off is that is also attenuates the signal by a factor of ten.
That is, 1/10 the signal applied to the tip of the probe actually reaches the input of the oscilloscope. • - analog and digital measurements in the channel reflect a drive's storage capacity and data throughput • - Today's high-speed digital networks use sophisticated protocols to ensure error-free data transmission. Yet, in many cases, monitoring the physical layer with a digital oscilloscope can pinpoint precious information that may not be revealed by protocol analyzers. • - For single-ended measurements, don't depend on mysterious ground connections. Always use a good, short ground connection.
• - This document collection describes how an oscilloscope probles can affect the circuit being measured. Many different types of effects and probes as described. • • - Have you ever tried to debug a broken signal that only worked when your probe was touching it? It may just mean you need a better probe to see what is really happening in the circuit. • - Ultrawideband real-time oscilloscopes exhibit maximally flat frequency response below the -3-dB point.
Therefore, the old rules that relate rise time to frequency response no longer apply. • - a test of a scope's high-frequency response is part of the calibration process • - New active-probe architectures make multigigahertz signal-integrity measurements easier and more accurate but only for those who understand how the probes work and the trade-offs among the topologies. Job keeps getting harder, but scope makers keep finding ways to satisfy ever-tougher demands. Wider bandwidth, quicker ADCs, and deeper memories are only part of the story. Giving designers insights and answers when they need them now requires more intelligence.
• • - Welcome to the Museum of old Tektronix Scopes. These pages give information on and images of old Tek scopes up to about 1970.
• - most frequently taken for granted and yet often least understood by audio engineers, article first appeared in the August 1982 issue of Recording-engineer/producer magazine • - A technical picture essay of the classic Tektronix 453 Analog Oscilloscope. Lots of pictures, descriptions of the various parts of the scope, and some troubleshooting information, too.
Links to other sites dealing with the Tek 453. • - get a solid understanding of oscilloscope basics • - this application note document from • - time you spend learning about the instrument's performance details can help you to spot waveform anomalies that you never suspected • - One of the common maintenance tasks for helical-scan video tape recorders (VTRs) is the adjustment of the timing of the heads relative to the video tracks recorded on the tape.
The main objective is to assure that any tape recorded on the VTR can be played on another similar machine without requiring any adjustments. The video tracking adjustment, typically done with an analog oscilloscope, requires a lively, gray-scale display. • - Read between the lines of banner specifications?bandwidth, sample rate, and record length?to drill down to the nuances and less glamorous features that affect efficiency and even the validity of your design. • - Fiber-optic telecommunication systems are moving data worldwide at 10 Gb/s, and future systems presently in development will be operating at 40 Gb/s. Even though the information is digital in nature, the actual signals are analog. A true digital pulse signal only possesses two states, either 'zero' or 'one.'
An analog-digital pulse signal possesses many other characteristics, including amplitude, rise/falltime, over/undershoot, ringing, long-term droop, etc. To design, characterize, and troubleshoot gigabit-per-second systems, engineers and technicians eventually need to observe the actual system pulse waveforms.
To make this measurement, engineers generally use a photodetector and an oscilloscope. • - This article describes new way of thinking about oscilloscope probe grounding. • - A probe can be any conductor used to establish a connection between the circuit under test and the measuring instrument. This conductor could be a piece of bare wire, a multimeter lead or a piece of unterminated coaxial cable. These 'simple probes,' however, do not fulfill the essential purpose of a probe; that is, 'to extract minimal energy from the circuit under test and transfer it to a measuring instrument with maximum fidelity.'
Build an oscilloscope • - low cost mixed signal capture engine configured as an RS-232 peripheral device, includes dual channel wide bandwidth DSO and 8 channel Logic Analyzer, circuit diagram freely available • - Notes on converting that old compact tv set or computer monitor into an oscilloscope. Proves very useful in line quality monitoring and other low frequency applications. • - Windows application that converts your PC with soundcard into audio frequency oscilloscope • - uses a matrix of 100 LED's for a display, published in Electronics Today International, February 1987 • - adapter attached to a TV set that changes it to low frequency oscilloscope Most oscilloscopes can perform only single-ended voltage measurements; that is, measurements of signals referenced to earth ground. Wiring within the probe connects the probe's reference lead to the shell of the BNC. When you plug the probe into the scope, the reference lead becomes electrically common with the scope's chassis. The power cord's ground conductor connects the chassis to earth ground.
In most oscilloscope applications the inability to make anything except single-ended measurements poses no problems. But oscilloscopes' single-ended inputs present challenges when you try to view signals that are not referenced to ground. A common example is the voltage across the switching device in an off-line switching power supply.
Another type of signal that you must measure differentially is a balanced signal. Simplest way of doing differential measurements is to use two normal 10X probes conencted to two oscilloscope inputs and the 'minus' operation to show the difference of signals between them. The normal 10X probe has a typical accuracy of?1% and gives a differential measurement accuracy (when using two probes) of two parts per 100. Using this 10X probe, the common mode rejection ratio of a scope and probe combination would be no better than 50:1. True differential measurements are safe and accurate way to measure signals that are not ground referenced. To make those measurements you need a differential probe. Unlike a conventional scope probe, a differential amplifier ijn differential probe has an input that is only implicitly referenced to ground.
As the name implies, a differential measurement produces a waveform that represents the difference in voltage between the two inputs. Ground does not enter into the measurement.Differential amplifiers ignore potentials that are equal in amplitude and phase and appear on both inputs.
This characteristic is known as 'common-mode rejection' (CMR). An ideal differential amplifier totally rejects the common-mode component.The other key feature of a differential amplifier is balanced input impedance (both inputs have identical impedance to ground, typically high impedance). A true differential probe has typically adjustments and electronics to provide common mode rejection ratios of 10,000:1 and higher. • - Oscilloscopes' single-ended inputs present challenges when you try to view signals that are not referenced to ground. Some work-arounds not only can mislead, but also can kill. True differential measurements are safe and accurate, however. • - These 'differential' type probes can be used in the same ways as the normal (resistor) probes, with some exceptions.
• - Will the real multigigahertz signal please stand up? Ultra-wideband digital scopes' 50 ohm inputs often make probes essential.
All manufacturers of ultra-high-bandwidth scopes also make probes and all now offer differential active probes appropriate to scopes with bandwidths as high as 6 GHz. A probe can be any conductor used to establish a connection between the circuit under test and the measuring instrument.
This conductor could be a piece of bare wire, a multimeter lead or a piece of unterminated coaxial cable. These 'simple probes,' however, do not fulfill the essential purpose of a probe; that is, 'to extract minimal energy from the circuit under test and transfer it to a measuring instrument with maximum fidelity.' Attenuating Passive Voltage Probes are the most commonly used probes today.
They provide a convenient and extremely rugged, yet inexpensive, way to acquire signals from your device under test. FET probes include active components (field effect transistors or other active devices) rather than passive components. The FET input results in a higher input impedance without loss of signal. • - small sizes and pad areas of surface-mount components make them difficult to probe but this simple tip helps it. • - Will the real multigigahertz signal please stand up? Ultra-wideband digital scopes' 50 ohm inputs often make probes essential. All manufacturers of ultra-high-bandwidth scopes also make probes and all now offer differential active probes appropriate to scopes with bandwidths as high as 6 GHz.
• - shown circuit diagrams of norma 1:10 probe and 1 kOhm resistive input style probe • - measuring clocks and critical signals accurately is often inconvenient and hard to do accurately with normal 10? Probes, this article describes 100? Probe that is easy to make and use, has a high bandwidth, and has a small (less than 1 pF) input capacitance RF probes allow you to examine high frequency RF signals (much higher that your scope frequency response) on your oscilloscope screen. The RF probes generally form a some kind of rectifier / peak sampler, which allows you to see the signal strenght as the signal which connects to scope input.
This allows you to quite easily measure signal amplitude and look at the moduleation (AM modulation). Rapidly changing voltages and currents in electrical and electronic equipment can easily result in radiated and conducted noise.
Electromagnetic interference (EMI) can be difficult to locate and correct in electronic equipment. A miniature EMI 'sniffer probe' and an oscilloscope can help to locate and identify magnetic-field sources of EMI. Typical EMI probles consist of some form of elecrical field sensing circuit (voltage proble) and some form of small coil (H-field probe). • - Probe switches automatically between AF and RF • - handly little gadget that lets you to 'look' at the signal and frequency output of radio transmitter with oscilloscope • - this miniature special probe and an oscilloscope can help to locate and identify magnetic-field sources of EMI • - DIY probes for checking electric and magnetic fields Typical oscilloscope does not usually sync well enough to video signal to be as such a convient instrument (when compared to special videomeasurement tools). With suitable accessories (usully special sync circuits), a normal oscilloscope can be used as a very nice video signal analyzing instrument. • - produces an oscilloscope trigger that synchronizes the horizontal sweep to a video signal that allows you to view any horizontal line by adjusting a potentiometer • - Digital-clock-period jitter is the variation in the period of a clock cycle compared with a nominal (average of many cycles) clock period. To accurately measure period jitter using an oscilloscope, you must subtract the oscilloscope jitter from the measured jitter.
However, oscilloscopes rarely have a jitter specification, so you must determine the oscilloscope jitter. One method of measuring oscilloscope jitter is to use the oscilloscope to measure the jitter of a pulse generator with known jitter. The ideal generator for measuring oscilloscope jitter would have zero jitter. This article shows a circuit for generating a calibration signal with near-zero timing jitter.
• - you can construct low-cost small test pices like filters, attenuators and terminators using coaxial panel jacks without pc boards or enclosures, design idea from • - this prescaler circuit, when plugged into the scope's external trigger input, can provide reliable, low-jitter triggering for both older and modern oscilloscopes • - Vintage triggered-sweep oscilloscopes find use in many applications. However, they have no internal delay line, so they can't display the pulse that triggers the sweep. Moreover, early laboratory scopes contain delay lines having insufficient delay to display such pulses during a uniform portion of the sweep. With such oscilloscopes, the true pulse shape remains a mystery. You can circumvent these limitations if you add an external delay line and equalizer. The scope can then display the exact trigger-point trace.
The instrument then becomes easier to use, and the measurements become more trustworthy. • - This article describes some impedance matching circuit for measurements. • - using two multiplexer ICs and some TTL logic), you can view eight analog or digital (or some of both) signals on the oscilloscope • - inexpensive and quick way to check the timebase speeds and linearity in vintage oscilloscopes Other oscilloscope links • - pages give information on and images of old Tek scopes up to about 1970 In those early years of computer-based measurement and automation, the desktop computer, linked by the General Purpose Interface Bus (GPIB), played an auxiliary role; however, the increasingly powerful PC has changed all of that. Today, the PC can acquire, analyze, and present data at increasing frequencies, resolutions, and sampling rates.In the dim and distant past, engineers recorded measurements with pencil and paper - a slow and error-prone method. Today, 20 years after the introduction of the IBM PC, two types of instruments - inboard and outboard - take measurements and move data into a host computer.
PC technology has become the backbone of automated test and measurement systems.Today virtual instruments are superseding the traditional kind by revolutionizing how measurements are made and the data shared. History of virtual instrumentation began over 15 years ago as PCs started coming into use in test and measurement as instrument controllers. The PC is now the most powerful and cost-effective approach to building instruments. Virtual instrumentation leverages the power, flexibility, and programmability of the computer and thus brings a wide variety of benefits. Laptop computers have further encouraged this trend with a form factor ideal for many portable applications. Even a basic normal modern PC can be used to do many different kinds of measurements with no extra hardware.
The soundcard found in most PCs can be used for various applications, althrough those applications are limited to audio frequencies and have usually quite limited absolute accuracy (PC soundcards are not designedprecise calibrated measureemnt instruments). With suitable software and soundcard you can use your PC as a signal generator that gan generate different waveform signals.
You can generate practically any waveform (within audio frequnecy band limits) if you use some suitable sample editor software or mathematics software to generate the signal waveform and then play it out through soundcard.With suitable software a PC with a soundcard can be used as a multi-purpose audio frequency signal analyser. You can for example use PC as audio signal oscilloscope, VU meter, spectrum analyzer, frequency response analyzer. PC can also used as a very convient recording device that can record and play back any audio signal.There are also special measuring instruments that can be connected to PC to expand it's capabilities. There are varieties that connect to PC bus or some PC interfacing port (like parallel or serial port).
The oscilloscope products that connect to PC through a slow port(serial, parallel etc.) and can sample at high rates are generallyimplemeted in the following way:The device has a buffer memory in it. When the device starts sampling(manual start or automatic trigger), it then samples it's memory fullat the given sample rare. After the data is sampled to memory itis stransferred to the PC. And the process can start all over.What comes to the software that controls commercial PC based measurign instruments there is one software that is more popular than anything else in the field: from. Has it's own competing on the same field. There are also measuring instrument manufacturer specific control software that is supplied with the instruments. • • - low cost mixed signal capture engine configured as an RS-232 peripheral device, includes dual channel wide bandwidth DSO and 8 channel Logic Analyzer, circuit diagram freely available • - This circuit is a buffer between oscilloscope probes and sound card.
It provides amplification and protection against high voltage input signals. • - software makes your PC to become an audio frequency oscilloscope • - with reasonable care and patience, you can design stable, accurate measuring instruments that live happily inside PCs • - JMM is data-acquisition software for digital multimeters equipped with a rs-232 port, such as the Metex 3850 and many others. The software is very simple to use and the control is straight forward.
• - Windows application that converts your PC with soundcard into audio frequency oscilloscope • - This circuit conditions different signals of frequency below 1 kHz and displays their waveforms on the PC's screen. • - Events beyond technology helped shape the way engineers use computers to automate measurements. This article tells what has heppened in this field. • - Time and velocity measurement via serial Interface (RS232), software and circuits in German • - Windows freeware utility for displaying spectrograms of digital audio files, works also real-time • - generate sweep test tones using PC soundcard, Windows program • - simple and easy to use shareware function generator for Win95/NT • - Some years ago, one of the fundamental electronic instruments was the laboratory curve tracer. A CRT display would sweep out terminal behavior (current versus voltage) from which you could derive mathematical models. From the displays, you could determine the bias points for optimum design performance.
Today, however, you rarely find the classic curve tracers in the lab. Instead, you find design-simulation software, such as Spice, that's removed from hands-on, empirical analysis. Spice models now exist for almost all electronic components. Characterization analyzers still make the voltage-current measurements but not at the design-engineer level. This low-cost circuit allows you to return to the hands-on approach by using your PC as a limited curve tracer. This curve tracer sweeps out seven logarithmic-scaled currents from 1?A to 1 mA while measuring the voltage, 0 to 5V (3.3V on some PCs), at each step.
• • - simple circuit and accompanying software turn a pressure sensor into an accurate and cheap pressure digitizer that works with any PC's RS-232C COM port • - with a few inexpensive components and INT1Ch, you can turn the printer port of your PC into a high-current ammeter • - Oscilloscope for Windows is a Windows application that converts your PC into a powerful dual-trace oscilloscope. Oscilloscope uses your PC's sound card as an Analog-to-Digital Converter (ADC) to digitize any input waveform (speech, music, electric signal, etc.) and then presents it on the monitor in real time, allowing the user to control the display in the same way as on a conventional 'standalone' scope, for example change gain, timebase or plot Lissajous patterns.
• - This page has links to many PC soundcard software, including waveform geenrators, oscilloscope and signal analyzing software. • - This web page describes how to modify Sound Blaster AWE-64 and SB16 to accept DC signals into their A/D-converter. With suitable software this allows a sound card to be used as a simple multimeter or oscilloscope that can measure also DC signals. There ideas described here sould be also adaptable to other sound card models as well. There are applications where you need to measure long cable lines that are used as transmission lines for various signals. There are many techniques related to transmission line measurements, because there are various factors that needs to be measured.
Most commonly measured transmission line characteristics are the following: • Conductor and shield resistance • Insulation resistance • Capacitance between wire pairs and/or between conductor and shield • Characteristic impedance • System impedance mismatch (return loss) • Line attenuation • Amount of noise coupled to line Let's say you have a long cable with a problem. Part of the cable is buried under ground, some of it runs through walls and floors.
You measure one end of the cable with an ohmmeter, and it reads about an ohm. So the cable is shorted. Hoping for the best, you cut off the connector and measure just the cable. Still reads about an ohm, so the short is somewhere else along the cable. If you could locate the short, you could save a lot of time and money by repairing just that one spot, rather than pulling in a whole new cable. TDR to the rescue!
You can use Time Domain Reflectometry to look at the characteristic impedance along the entire length of the cable. Cables used to carry high frequency electrical signals are generally analysed as a form of Transmission Line. The amount of capacitance/metre and inductance/metre depends mainly upon the size and shape of the conductors. The Characteristic Impedance depends upon the ratio of the values of the capacitance per metre and inductance per metre. To understand its meaning, consider a very long run of cable that stretches away towards infinity from a signal source.
The result, when the signal power vanishes, never to be seen again, is that the cable behaves like a resistive load of an effective resistance set by the cable itself. This value is called the Characteristic Impedance, of the cable.
Return loss (RL) is a measure of the reflected energy caused by impedance mismatches in the cabling system. Reflections create an unwanted disturbance signal or 'noise' on the cabling link that potentially interferes with the reliable transmission over the link.
As a noise source, return loss is measured and evaluated to assure that the reflected signal energy is sufficiently small in reference to the transmitted signal such that the reliability of the transmission is not negatively impacted. Return loss is an important characteristic for any transmission line because it may be responsible for a significant noise component that hinders the ability of the receiver when the data is extracted from the signal. It directly affects 'jitter.'
Return loss is one number which shows cable performance meaning how well it matches the nominal impedance. Poor cable return loss can show cable manufacturing defects and installation defects (cable damaged on installation). With a good quality coaxial cable in good condition you generally get better than -30 dB return loss, and you should generally not got much worse than -20 dB. Return loss is especially important for applications that use simultaneous bidirectional transmission. Opens, shorts or less-severe impedance discontinuities have a way of showing up on cables in strange places - places you might never suspect. These can occur on coaxial transmission lines or twisted-pair lines. Such opens, shorts or other impedance discontinuities are called faults.
The location of faults cannot be determined with simple ohmmeters. Even the existence of certain faults cannot be determined with an ohmmeter. Time domain reflectomer is an instrument often used ot locate such faults. Time Domain Reflectometry measurements (sometimes called Time Domain Spectroscopy techniques) work by injecting a short duration fast rise time pulse into the cable under test.
The effect on the cable is measured with an oscilloscope. The injected pulse radiates down the cable and at the point where the cable ends some portion of the signal pulse is reflected back to the injection point. The amount of the reflected energy is a function of the condition at the end of the cable. If the cable is in an open condition the energy pulse reflected back is a significant portion of the injected signal in the same polarity as the injected pulse. If the end of the cable is shorted to ground or to the return cable, the energy reflected is in the opposite polarity to the injected signal. If the end of the cable is terminated into a resistor with a value matching the characteristic impedance of the cable, all of the injected energy will be absorbed by the terminating resistor and no reflection will be generated.
Should the cable be terminated by some value different from the characteristic impedance of the cable the amount of energy reflected back to the cable start point would be the portion of the pulse not absorbed by the termination. Also any change in the cable impedance due to a connection, major kink or other problem will generate a reflection in addition to the reflection from the end of the cable. By timing the delay between the original pulse and the reflection it is possible to discern the point on the cable length where an anomaly exists.
The cable type governs this signal propagation speed. For example normal Category 5 cable propagation speed is 66% the speed of light, and for most coaxial cables this value is between 66% and 86%. Other cable characteristics are usually easier to measure and can be done with more conventional instruments. Cable conductor resistance can be measured in installed cable by shorting the cable on one end (short center wire to shield on coax, short two wires in wire pair on twisted pair cable etc.), and then using a multimeter on the other end to read the resistance value.
Cable capacitance can be measured with a capacitance meter by leaving one end of the cable not connected anywhere (all wired free) and connecting the meter to the other end of the cable. Cable insulation is typically measured with an insulation resistance meter.
The cable is typically not connected anywhere (or connected to equipment that do not cause error in measurement and do not get damaged by measuring). Insulation resistance meter typically applies some quite high voltage DC (125V, 250V, 500V, 1000V) to the line between two wires and measure if there is any leakeage. The leakage current is measured and the result is converted to resistance (usually in megaohms to gigaohms range). The measuring voltage needs to be selected based on the ratings of the wiring (and equipment if such are connected).
Low voltage telecom wiring and similar is typically tested with 125V or 250V voltage. Higher voltages are usually used when testing the insulation on the mains power carrying cables and some radio transmitter coaxial cable systems.
The measurin voltage needs to be right for the intended application. Too low voltage might not reveal insulation problems, but too high voltage can damage wiring and equipment connected to it. Line attenuation can be measured by connecting the signal source used in the application (or test instrument generating suitable signal) and signal receiver on other end (receiving equipment or terminating resistor).
Then you just mesure the signal level on the transmitting and receiving ends (using a suitable multimeter or oscilloscope or similar instrument). The difference on those tells how much the cable attenuates the signal. In some applications you need to do measurement with different frequencies, recording how cable attenuates on different freuqncies. Some cable TV system measurements use a wideband noise source as the transmitter and a spectrum analyzer as the receiver (difference on the signal spectrum on the transmitting and receiving ends tells the attenuation on different frequencies). Amount of noise coupled to the line is measured with the indended equipment or suitable line terminators connected to the ends of the cable. If you use equipment they need to be turned off so that they do niot send anything to the line.
Any signal that is now measured on the line is the amount of coupled noise. • - From Wikipedia, the free encyclopedia • - Very many cable fault locating documents. • - dealing with CATV distribution equipment and power supplies, we are constantly confronted with shorted and open components and circuits • - a schematic for a homebrew cable reflection tester from the December 1996 issue of Electronics Now, useful for checking coax cable runs for shorts or even impedance mismatches • - This article illustrates the relative influence of skin-effect and dielectric losses on the characteristic impedance of a lossy transmission line. • - knowing how to measure PCB trace impedances can help you optimize circuit performance from DC to gigahertz • - Opens, shorts or less-severe impedance discontinuities have a way of showing up on cables in strange places - places you might never suspect.
These can occur on coaxial transmission lines or twisted-pair lines. Such opens, shorts or other impedance discontinuities are called faults.
The location of faults cannot be determined with simple ohmmeters. Even the existence of certain faults cannot be determined with an ohmmeter.
• - You can use a multimeter with capacitance-measurement capability to measure the length of wire or cable to an open circuit. The capacitance of a pair of wires (or a wire to a shield) is directly proportional to the length of the wire. If you know the capacitance per foot of wire, then you can calculate how far it is to the open circuit. • - This is introduction to one particular TDR model. This document includes good TDR trace example pictures. • • - The TDR (time-domain-reflectometry) method for signal-integrity analysis can help gigabit-system designers produce more accurate interconnect models, resulting in more reliable and higher performance designs. • - describes basics and shows a transmission line demonstration setup • • - usage techniques and application notes • - simple TDR circuit to be used with an oscilloscope • • - analysis of a conductor which can be used for example to detect telephone tapping devices • - many TDR papers, some on cable measurements and some for other applications • - TDR Training Presentation Proper testing of wiring system after installation is essentialto guarantee good operation later.
The cabling system needs to bemeasured after installation and the results of those measurementsshould be documented for later use. Measurement is also usefulduring use when cabling problems are suspected.The most common cable fault is an open circuit, usually due toproblems close to or at the ends of the cables. A simple ohm metertest generally suffices.
For multiplair cables where cable ends are many wires inside, a simplemultimeter is bothersome. For those applications multi-pair cabletestes which find showrt circuits and broken wires are a good choise.In some application you need to measure the cable length. Dependingon the cable characteristics you know and the measuremenet instrumentsyou have, you can use a multimeter (resistance measurement), RLC meter(capacitance measurement). Time domain reflectometer (pulse tesing)or signal ateenuation testing (signal source and level meter)to measure the lenght of the cable you have installes somewhere.
General information • - Very many cable fault locating documents. • - idea how short and open circuits can be located relatively easily Simple single wire testing • - audible output if resistance is less than 300 ohms • - offers a short-circuit test current of less than 200uA and detects resistance values of less than 10 ohms Multi-wire cable testers Engineers have long known how to test a cable for continuity by simply connecting all conductors in series and checking with an ohmmeter. This method is sometimes impractical, however, because it cannot check for short circuits (or you need to make very many test to measureresistance between very many wire combinations).
To solvel thos problem on multi-conductor cables, there are specialcable testing instuments designed for this. • - This simple microcontroller based cable tester verifies the correct wiring of the cable, up to 8 conductor cables. • - Engineers have long known how to test a cable for continuity by simply connecting all conductors in series and checking with an ohmmeter. This method is sometimes impractical, however, because it cannot check for short circuits. This simple method solves the short-circuit detection problem. Connecting LED indicators at each shorting loop provides a visual indication. Cable test tone senders • - This audio signal tracer/injector will undoubtedly prove to be very useful for many routine servicing operations.
The unit consists of an audible signal monitor for 'listening' to the signals present in an electronic device (such as an audio system, receiver, amplifier, or tape deck) at circuit points inside these devices. It also includes an RF detector probe and signal generator.