how to measure high voltage with oscilloscope

You can see that reflected in the chart in the article above. Before I found your site, I tried making a probe with 200 Meg HV resistors with a 1,000:1 ratio, and then a 1 Million:1 ratio, and both read low like the Tek probe. In that case you can try looking up yourspark length and electrode configuration in a chart. The largerthe sphere diameter, the higher the voltage they get to beforethey no longer closely follow the 30kV/cm line. If you want to measure 70VDC, then you need a voltage meter, commonly known as a multimeter these days. It can then be easily seen that A (the multiplier for cm) must be smaller than B the multiplier for inches. Using an oscilloscope to measure currents requires converting a current to a voltage, and this can be done a few ways. Shame on me too since Im such a huge fan of dimensional analysis. The following picture shows how the electrical . Here is how to measure high voltage using an oscilloscope: Step 1: Turn on your oscilloscope. Everything you need to know about PC oscilloscopes from Advanced Triggers to Zooming. Electromagnetic Interference (EMI) alternately known as Radio Frequency Interference (RFI) when it arises in the radio frequency spectrum is an obviously bad effect on a variety of levels. Up-to-date versions of the documentation supplied with your products in PDF format. Voltage Range Selection The oscilloscope is divided into two main sections. To determine the capacitance we will measure the time that it charges to a specific voltage. Why does it go further than straight across? Does anyone have experience with an application like this? It is possible to do this well but not as trivial as it appears here. hm400 40mhz analog oscilloscope . Everything you need to know about PC-based data loggers from Alarms to Zooming. @raelik PT-104 High Accuracy Temperature Data Logger, Pico wins Best Oscilloscope Manufacturer of the Year, Pico presented with the Queens Award for Enterprise, PicoByte and AC Coupling: When to use it and why, Differential and floating voltage measurements, Balanced high-impedance inputs for a low circuit load. The input voltage range is 0 to 2.5 V and the resolution is 2.5 mV. A few notes from my previous experiences: 1. Construct a resistive potential divider that say operates to reduce the input voltage by 1000 to 1. kV = 30 * d(cm) Then start. The High-voltage Probe Selection Guide asks you the intended measurement application, offering a choice of power semiconductor test, floating sensor or system inputs /outputs measurements. I understand very little of this but in the automotive world we use spark gap tool to measure the ability of an ignition coil to produce voltage. The HV probe has a very high resistance such as 1000 meg ohms. Proper Measurement Techniques Using an Oscilloscope Probe Before attempting to measure ripple or transient, some background on probing with an oscilloscope should be discussed. but we are looking for the ability of the coil to produce a spark that is capable of jumping at least an inch when full charged and good battery voltage. My little one can pull arcs of almost two feet and happily light a strip light across the room. 5. The shape of the electrodes plays a bigpart, as does the pressure and temperature of whatever is in the gap,usually air. Meters with other impedances can be used with thehelp of an external shunt or a correction factor, all of which isdescribed in the probes documentation. This high-speed oscilloscope has two channels that sample at up to 1 GS/s with flexible settings for coupling and input impedance, an input voltage range of up to 100V and an offset of up to 250V. Measuring the voltage of a circuit with a probe loads it both resistively and capacitively, and at high frequencies, . 2 Connect the probe with the Oscilloscope input channel 1 (slightly rotate the joint until it perfectly connects with the input port). I stated that the probes are for DC and low frequency AC only, but that applies to the spark length trick too. When your spark gap is at the maximum distance at which you get a spark then just before the spark happens is when you have your maximum voltage. I have re-read your replies but still think the outcome is incorrect. For added protection for the meter from high voltage I added twospark gaps inside in case some of the resistors shorted. For inches, the formula is: In the photos above, the measured voltage is 17kV. That means we can say that to get the actualvoltage you simply multiply the measured voltage by 1000(75V x 1000 = 75,000V). An inch is longer than a cm ==> kV/inch must be greater than kV/cm. Hi Steven This site uses Akismet to reduce spam. R1 was lastlyselected so that R2||R3 would have a useful voltage range across it. August 20, 2014 George 0 Comments. For example, the image opposite shows how a CAN bus differential signal is the difference between CAN High and CAN Low and how any common-mode noise is rejected. By using our website and services, you expressly agree to the placement of our performance, functionality and advertising cookies. We strongly recommend that you donot adopt this solution. oscilloscopes also have a maximum voltage that can be measured, usually around 1000V, and that should be marked somewhere near the input connector. Assuming your scope is properly grounded which also means the input connectors outer ring is also grounded (verify with a DMM). It can be tempting to take the direct approach and disconnect the ground lead at the mains plug. Most oscilloscopes are designed with the expectation that one of these points will be fixed firmly to ground, and so the reference lead of the probe connects electrically to the shell of the BNC input, which connects to the chassis, which is grounded through the mains lead. The larger thespheres, the closer the measurement should match the formula, for acertain voltage range, but more on that below. You are correct about the voltage. 3) Voltage at the diode output (s) 4) Voltage at the output of each capacitor. JavaScript is disabled. Yellow: There are some compromises in performance of the probe in this application, though some users may find the probe works fine for them. level x-position volts/div. If the Picoscope software allows you to set probe attentuation, you can set it to 10X and the displayed voltage will be correct--it will multiply the actual voltage that it sees by 10X. I initially tried using a Tektronix 40kV high voltage probe, but I got a value of 3kV P-P. That seemed very low based on the diameter of the plasma, about 6mm. Does air humidity have an impact on the dielectric breakdown value? Ive used darkness for that reason, but also sometimes when I want the corona but need to have it in specific places. The larger and rounder they are, the higher the voltage before a spark occurs. This allows the oscilloscope to be set to the appropriate full-scale range, with a sensitivity of 200mV or 2V per division. Calibration equipment is a breeze with that feature. We measure the voltage over the capacitor directly with the first channel of the oscilloscope. If the gap is 1 inch, your formula implies that the gap in cm is 1/2.54 = 0.39 cm, which is clearly not true. The schematic on the right is a simplified way of looking at the circuitwith R3 pulled out of the meter and combined with R2. However, these are more user-friendly: - These from Vishay are suitable up to 3kV. LikeReply MrAl Joined Jun 17, 2014 9,205 Jun 9, 2018 #6 DickCappels said: Use probes rated for the maximum volts you will encounter. 10 resistors will give you 10:1 reduction. I input 12vdc at under 1 amp throughout. You need high voltage wire rated at the voltage you are putting out, or a lot will leak out of the wires, just because you see a 10 inch spark doesnt mean you are getting anywhere near the voltage out you think you are! However you can measure it manually by 'counting' the vertical reticules and multiplying by the volts per division. Fromthe photo you can see they consist of rounded solder bulbs, spaceda precise distance apart from the metal end caps of two resistors. It requires a power source, either battery, mains adaptor or a special interface to obtain power from the scope. Just an Idea so far; some Serious design help needed here. The oscilloscope photo below shows this changing voltage. Engine compression high voltage ignition voltage? My coffee hasnt kicked in. This one is designed for use from 1kV to 40kV DC, with accuracy varyingfrom 1% to 2% depending on the temperature, and not including theaccuracy of the meter. In Beyond the Multimeter, we look at five examples of how reaching for an oscilloscope . can be used as components in custom applications . .. E=mc (+/-1dB) Voltage drop < 1 V (of course, more voltage drop will create voltage imbalance and current spikes, see the schematic) Power dissipation < 0.5 W. You must be very careful when measuring voltages on the mains with any measurement instrument. Your scope is 'protected' to +/- 100V, so even if you make a mistake you shouldn't blow anything up. You can also try any one of the following methods to measure the voltage with an oscilloscope quickly: You can use the on-screen cursors to take the voltage measurement between the two points, i.e. It can be done without R2but that would put the meter in danger of having a high voltage acrossit. Lets say 10 cm = 4 inches (not quite right, but keeps the maths simple). And yes 2.54 cm = 1 in but you cant substitute 2.54 cm to get inches. Mar 31, 2020. Power quality in the context of ac lines usually refers to how closely the ac line comes to approximating the ideal sinusoidal wave. Youre right in saying that inches are longer than cm totally agree. 76kV per inch is the generally accepted value for the dielectric breakdown of air. If you use a normal 10X probe, the voltage at the scope input should be 1/10 of actual--so 7V in your case. Let us know in the comments below. It starts as a spark with zero gap. Thats a good point. A good solution with the following advantages: There are several brands of differential input oscilloscopes available providing a choice of bench, handheld and PC-based form factors. spark length = 10mm = 1cm = 0.3937in, 3kV/mm x 10mm = 30kV 555 timer- wire up a 555 timer to pulse at ~500Hz Plug your coaxial cable into the oscilloscope. This is the basic technique of measuring voltage using an oscilloscope. System input/output measurements include the line-side AC voltage, DC/DC converter high- or low-voltage inputs or outputs, DC bus or link, and inverter drive PWM outputs. http://hackaday.com/2016/06/15/wrangling-high-voltage/#jp-carousel-209541 1. The voltage before the spark occurred is related to the spark length, which is also the spark gap width. The Fluke is good for up to 40kV DC but Ive had to measure higherand so I made my own probe. The calculationsfor that are very involved so I wont go through them here. A much safer and commonly used method is to use two probes, invert one channel and use math to subtract one channel from the other, so now we only display the differential signal, and all perfectly safely. So if scope is set for 50V / div, then set trigger to 2 boxes on screen. There are two transmission vectors, equally problematic. So if the terminals on your spark gap are different sizes and the smaller one is positive you get substantially longer sparks. This includes capturing MOSFET/IGBT gate drive and output signals, then analyzing them. You can find th. Since you study spark gap. If youre designing an HV system and are getting ticking (small, localised breakdown) a long acrylic tube makes a useful ear trumpet to help identify the offending bit of the circuit without getting your brain tickled. The resistors were all soldered together with big, round solderbulbs to avoid sharp points which can cause losses due to ionization. #4. We used to use this a lot and you REALLY know when youve hit the right spot. Select the "AC voltage" mode by turning the tester knob. This Week In Security: OpenSSL Fizzle, Java XML, And Nothing As It Seems, MoCA Networking Is A Niche Solution For Coax Lovers, Make Your Pi Moonlight As A Security Camera, Commodore Datasette Does Its Own Calibration, Decoding Rediscovered Rope Memory From The Apollo Guidance Computer, IR Remote Tester Helps You Crack The Code. For the horizontal section, set the dial with MAIN TIME/DEV to 0.1ms Another thing is in order to actually output the voltage a power supply is putting out, you need roughly one inch in diameter electrodes for every 100,000 volts, so 2 for 200,000, 3 for 300,000, so if you have a power supply that is putting out 300,000 volts but you only have half inch balls on the electrodes you will never get anywhere near 300,000 kv out. If we apply theformula for a 5mm spark gap, we get 3 x 5mm = 15kV. The digital multimeter is the mainstay of electrical troubleshooting and the tool that most of us reach for first. Storage of waveforms on my Laptop is very easy allowing me to quickly email waveforms to my Colleagues. The display of the oscilloscope is divided by vertical and horizontal lines. Connect the center (axial) portion of the cable to the signal, and the side (usually an alligator clip) to ground. Multiply again by 1,000 to obtain the true reading scaled by the probe. + V and - V), as in a the spark length) is . The input resistance is 1000M. The air in the gap would still be fairly ionized before the next spark occurs, lowering the voltage needed for that next spark. But its not quite so simple. Crudely measure your body-voltage by using an oscilloscope to compare it to a high-voltage power supply. Except it had insulating plates going down its length. You'll need several resistors to do this of probable value greater than 1Mohm and they'll need to have a voltage rating that is suitable. Stefan Dzisiewski-S (@stefandz) is obviously correct. Just use some 1M resistors to create a voltage divider. Replace all my GAPcm / 2.54 up there with GAPcm x 2.54 so GAPin = GAPcm x 2.54, Y x CAPin = 30 x CAPcm, this Y x GAPcm x 2.54 = 30 x GAPcm, thus Y x GAPcm = (30 / 2.54) x GAPcm, and Y = 11.8. This method is good for a rough estimate. PicoLog 1216: This has 16 analog input channels. Testing However, correcting the formula in the article would help make it useful for a wider range of people. More resistors run at a voltage further within their maximum rating = more linear over a wider input voltage range. In desperation, I tried measuring the maximum spark gap length using my homemade probe. Thats because of the following When a spark will occur is partly dependent on the shape of the electrodes on either side of the spark. Figure 2 shows the selections for probing a 260 Vdc GaN transistor: In a future post, we'll go over more of the reasoning behind this selection when we discuss probing requirements for GaN power semiconductor measurements. The second formula in thediagram shows how the voltage across R2||R3 is calculated. Customer service gave me first class service. ADC-20: This has 8 single-ended or 4 differential high-resolution analog inputs. The first is the measurement technique when utilizing an oscilloscope probe, while the second relates to the specific conditions under which that data is specified. We were a bit hesitant at first but it worked flawlessly, and everybody is now out shopping for PicoScopes! I have been using my 4224 PicoScope for years. Essentially I need a very high power switch that goes short circuit when it sees 600Vdc across it, and can take an initial current of 20kA. Adjust the vertical setting to display the complete waveform and determine the value by . Nope, since 1 inch is longer than 1 cm, you have to make the other side of the multiplication smaller to arrive at the same voltage value. intens focus trace. Can you give me some idea of the mistakes I could be making? The primary function of an oscilloscope is to measure voltage waves. (forgot this one, and it may be the most important!) However, if you're measuring the setup-and-hold times of a high-speed signalsuch as the NAND data lines on a solid state drive (SSD)then you'll want to use two active high-speed differential probes. When you want to measure shifting signals, things get a little trickier. ]. Not sure if this will be visible to all, and is a little off track. Because of all this its a pain to accurately guess voltage with spark gaps, unless you understand all these factors. The principal reason for the code is shown right on the screen, with more more information behind the "i" button. Centimeters are longer than Millimeters, so the needed multiplier is larger and it is. Bye Bye Linux On The 486. Assuming that chart is excel based, use the x-y scatter and it will automatically space the data out properly. R1 and R2||R3 form a voltage divider. The high value resistor is the greatest contribution to error so I start out with Caddock USF300 series resistors with 0.01% tolerance and 5ppm/C drift. This high-level categorization determines the relative importance of many possible probe specifications, including the voltage range, bandwidth, attenuation and isolation. That is unless youre working withVan de Graaff generators, but even then usually only the dome isspherical and the other electrode isnt. When making the measurement, take the reading on the meter oroscilloscope and multiply it by 1000. This type of application usually determines the isolation requirements of the probe, as the signals involved are generally small with large voltage offsets. Together theyre usually labelled as R2||R3. "The maximum displayed trace on the scope is 8 vertical divisions of 5V per division = 40V maximum ". The peak voltage is 2 squares or 2 DIVs, the VOLT / DIV switch that we set is 5 Volts then the calculation is 10 Volts (2 DIV x 5 Volts = 10 Volts) While the peak voltage to the peak is 20 Volts with the following calculation: 4 DIV x 5 Volts = 20 Volts Then the result of measuring ac voltage is 20 Volts Measuring Frequency with an Oscilloscope Perfect Partner for Development of Encoder controlled Stepper Motor Actuators. Differential Probes Advanced Analysis The modern digital oscilloscope can perform many specific analysis tasks that allow the user to get to an answer quickly and easily. It is a great scope. Ball plane gaps have this effect too if the plane is negative and the ball positive. Digital Multi-Meters (DMMs) don't measure current directly. Silicon (Si), Silicon Carbide (SiC) and Gallium Nitride (GaN) are all popular materials for semiconductor devices, each with its unique requirement on rise times for the switching signals: The larger the voltage swing, the slower the rise times get to help keep EMI in check. You can measure and view either DC or AC signals up to the oscilloscope's BW using the standard voltage vs time mode of operation. the transient. 6. High-voltage circuits that also have high-speed devices, such as the recently introduced gallium nitride (GaN) and . Best to not have to explain why a curve doesnt look quite right. Hi. Thats how I went from the17V shown on the scope to 17kV in the example above. I tried to measure the HV node of a plasma tweeter, which uses a modulated power oscillator running at 27 MHz to drive a tesla coil and ionize the air in a confined space (the throat of a horn). Learn how your comment data is processed. An oscilloscope is the wrong tool for the job. Most resistors have a significant voltage coefficient, particularly with a significant potential across them. The High-voltage Probe Selection Guide on the Teledyne LeCroy website is the starting point for choosing the best high-voltage probe for your application. This device is suitable for measuring multiple channels at higher speed. kV = 30 * 2.54 cm/in = 76.2 kV / in First, connect an oscilloscope's input to a metal plate. ), Youve got your math reversed there. The output voltage measurement is limited to a safe range between 0 and 2V (Lo Range) or 0 to 14V (Hi Range). Step 4: Adjust the scope's vertical sensitivity to 1v/division. when. Showing you how to get the most out of PicoScope oscilloscope software. Measuring current is a straightforward process; connect a multimeter to the circuit you wish to measure, and the meter will provide you with a clean result to work with. You may have used a line chart or something which sets each horizontal point out equidistant from the next. Even your multimeters might not be working correctly at 1.1 - 3 kHz. Inches are longer than Centimeters so the needed multiplier is larger and it needs fixing. We can measure the current by connecting a resistor in series with the capacitor, measuring the voltage over the resistor and calculating the current in the circuit. So often a more elegant solution is required. You have to multiply in order to cancel out cm. Set the oscilloscope to AC coupling for now (I'll explain a little bit more about this at the end of the tutorial) As long as the probe is rated for the voltage it will work, and just about any common x10 probe should be rated for several times more voltage. There are many considerations to selecting the best high-voltage probe. What? For example, for a 4 cm gap and 5 cm spheres as electrodes, you get 90kV whereas for a 4 cm gap and 25 cm spheres as electrodes you get 110kV. These distances must have the same breakdown voltage, which implies that A x 10 = B x 4. Scuff on a carpet (during a low-humidity day), wave your hand near the metal plate, and see how much the trace on the oscilloscope is deflected. You'll need to tweak it manually. Beyond the multimeter, part 2: using a multimeter and an oscilloscope to troubleshoot transient voltages in variable frequency drive output. Since GAPin = GAPcm / 2.54, then Y x (GAPcm / 2.54) = 30 x GAPcm. 6. Ill talk about doing more precise measurements when I talk about high voltage probes further down. This made my decision much easier when I was looking to buy an USB scope. I have a Tektronix TDS2002C oscilloscope and need to measure high voltage in the range of 1000 ~ 10,000 volts AC, referenced to ground, in the frequency range of 1.1kHz - 3kHz. Dumb question but if your probe in switchable probe in 1X handles upto 300V and your scope handles 400V, and the absolute highest voltage you ever expect to see is 120V, whats are some reasons to use 10X? 30kV in / 2.54 cm != 11.8 kV/in (I mean, mathematically it does but not in the real world) It equals 11.8 kV in / cm. select. Youve made a logical error. Most modern oscilloscopes provide the option to measure DC voltage automatically. The maximum displayed trace on the scope is 8 vertical divisions of 5V per division = 40V maximum (without using the Y control and any voltmeter display) Divide this by 2 to get peak to peak Frequency range = 100 kHz. from top and bottom of the waveform. The highest Ive used it for is 75kV DC,though its designed for a maximum of 150V at the meter,which equates to an input voltage of 150kV. I have Tektronix TDS 1002 oscilloscope for measurements. I talked about that in the tips and tricks section of this article on flying lifters http://hackaday.com/2016/07/13/expanding-horizons-with-the-ion-propelled-lifter/. Show your Pico-based products to the world. Want to share hints, tips and code with other developers? Using Standard Measurements Many of these probes are meant for oscilloscopes and do have a BNC connector. Depending on which semiconductor device is being tested, ideal probe features could include wide voltage range, offset capability, very good CMRR and higher bandwidth. The key advantage is that the differential inputs allow the use of inexpensive passive probes. Sometimes, it may be the only safe choice. For example, if only individual DC voltage measurements are needed, then a passive 1 M single-ended voltage probe would be required. PicoScope, Pico data logger and RF products Open the High-voltage Probe Selection Guide, answer the three basic questions, and you will get a recommendation for a high-voltage probe with notes on our reasoning behind the choice. Clearly, these answers cannot both be correct. Brass dome nuts are very useful if youre creating a higher power load where connections are bolted as opposed to soldered. https://probemaster.com/3900-series-scope-probes-100-mhz/, Quote from: rstofer on 22 Sep, 2020 19:36, Quote from: Refrigerator on 22 Sep, 2020 20:49, Quote from: JustMeHere on 23 Sep, 2020 05:09. The phase is split (L1=+180deg, L2=-180deg). Its for use with a 10M +/-1.0% voltmeter, or oscilloscope as in thephotos above. Time scale frequency f=1000Hz, then period T=1/f=1 (ms), namely tab=nT (ms). The same holds true with van de graaff generators if the top is negative output and you use a smaller ball grounded to discharge sparks from the larger ball you get longer sparks. Step 3: Connect the probe's ground crocodile clip to a reliable grounding point. Above that is the real data. This video demonstrate three methods to measure the voltage and harmonics of an AC power supply using a USB oscilloscope with passive probes. High voltage circuits often dont have much sparecurrent for measuring purposes. [voltage] = [11.81] x [length in inches]. The other is with the analog meter again but Im holding the probe in myhand. kV = 76.2 * d(in) I had thought about manual switches but I am not sure if the arcing will cause an issue with the specific waveform I am trying to generate. Youre trying to solve this Y x GAPin = 30 x GAPcm. On the right side of the scope, you see different buttons in the panel. If you use a normal 10X probe, the voltage at the scope input should be 1/10 of actual--so 7V in your case. And when spark gap is at minimum distance it gives maximum voltage to lifter.Because spark gap is a short circuit. HV probe selections for measuring a 260 Vdc GaN transistor. all my designs have the safety earth (for the spark gaps) as a ring crimp connection that way you cant pull it out so easily if youre being vigorous! Figure 2. Use on screen cursors to take a voltage measurement between two points (top and bottom of the waveform) Use voltage peak-to-peak measurement Use a built-in DVM Learn more about oscilloscopes Check out Keysight's low-cost oscilloscope How do you measure capacitor voltage on an oscilloscope? The above chart summarizes all of this. Re: Measure higher voltage using oscilloscope. Oscilloscope. My design so far involves charging a large capacitance and rapidly discharging it through an inductor, but the switch connecting the capacitor to the inductor needs to briefly take about 20kA peak. 3. The high resolution Vds information obtained, can be used for indirect measurements such as: Measuring RdsON . However, there are also limitations. I hadnt thought of using brass dome nuts. Analysis includes dead time verification and switching loss measurements. To help distinguish between the models in this study, we've created a list of crucial performance factors to help cut through the . I still maintain my point GAPcm != GAPin / 2.54. Just a slight 'oopsie' with the switch and things get expensive. When measuring voltage, connect the terminal of the voltmeter in parallel with the part you want to measure. Here are two more photos of where Ive used the Fluke probe. 2. I got there in the end if you read my many replies. You can even use the built-in DVM. power. 720. Expected resolution = 5 A/division. If your circuit has a spark gap then when a spark occurs, thats ashort-circuit, dumping all your built up charge. I have a solution for that too. You are saying 1cm gap is 30kV and 1 inch, which is 2.5 times greater, is 11.8kV. Since the included software is really stable, this type of device is a great tool for great tasks! We say a voltage is floating when it is not directly referenced to ground, and similarly a voltage measurement is "differential" when measured between two points neither of which is ground.

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