Several measurements need to be made to select the right NTC. (20 min) When the scope boots up you should see the divisions, scale, and a noisy, flat line of a waveform. If you were sampling much slower the current might appear to rise instantaneously. This video shows two very simple methods of using the oscilloscope to measure current. Push the inrush button, on the face of the meter. A series of measurements are made to determine the maximum inrush current. But you can configure the oscilloscope to measure current as well. AC6801B AC source measurement panel displaying AC current peak, peak hold, and rms. Most scopes have this function. An oscilloscopeis typically set up to measure voltage versus time. Connect and share knowledge within a single location that is structured and easy to search. For higher power DC/DC converters, the input inductor may need to be unacceptably large or expensive to . This content cannot be displayed without JavaScript.Please enable JavaScript and reload the page. Making statements based on opinion; back them up with references or personal experience. Step 2: Plug in the high voltage probe into channel 1 [CH1] of your oscilloscope. Also the company name (first word) should be Littelfuse with 'el', not LittleFuse. 503), Fighting to balance identity and anonymity on the web(3) (Ep. Figure 2. Left 0 degrees, middle 30 degrees, and right 180 degrees. Most likely, the spike was from all the bypass caps we had. The turn-on phase can significantly affect the inrush current. Using an oscilloscope to measure currents requires converting a current to a voltage, and this can be done a few ways. I back up all my circuits with scientific research, solid engineering, and stellar customer service. 1,416 Oct 28, 2015 #2 Place a one ohm resistor or even 0.1 ohm resistor in the positive lead and measure the voltage across the resistor. An example is lower capacitance or lower inductance. LittleFuse provides a very nice app note with a lot of details for the design of these kind of devices. Many oscilloscope probes have a switch that allows you to switch between "1x" and "10x." The good thing about PTC fuses, in this context anyway, is that they take a bit of time to heat up enough to "blow" i.e. Contact Sales for product demos and consultations. Plug the probe into the input of the channel you want to use on the oscilloscope. It works the same as an electrician's clamp-on ammeter, where heavy-duty jaws clamp around the conductor in which the current flow is to be measured. Stack Exchange network consists of 182 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. Set the oscilloscope to AC coupling for now (I'll explain a little bit more about this at the end of the tutorial) http://se.farnell.com/lem/cksr-6-np/current-transducer-6a-5v/dp/2146828, Quote from: tautech on August 22, 2015, 10:21:21 pm, Quote from: Circuiteromalaguito on August 23, 2015, 03:47:42 am, https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg, http://www.dx.com/p/hantek-cc-65-ac-dc-current-clamp-meter-multimeter-with-bnc-connector-blue-black-197938?utm_source=GoogleShoppingAU&utm_medium=CPC&utm_content=197938&utm_campaign=428&tc=AUD&gclid=CNnM3Zj23rkCFUpZpQodBgcAYg#.VdwRkH3oSf4, Quote from: ez24 on August 25, 2015, 07:38:26 am, Quote from: alsetalokin4017 on August 25, 2015, 07:21:37 am, Quote from: Circlotron on August 25, 2015, 11:55:54 am. An oscilloscope is typically set up to measure voltage versus time. To answer your question, how you measure the inrush current with an oscilloscope, you can improvise a current transformer: - get a ferrite tor (for example from a broken PC power supply, if you happen to have any, or from a filter gland like those you see on various cables This current measurement will be the startup current? Alternatively, you can use a current probe. Request Repair / Calibration Now that we've seen how to select a value of Rsh and measure current flowing through it, let's take a look at how we might configure our oscilloscope to measure current. input 1000 V,. Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. @Oli I'm assuming it does not have persistence refresh. For that, you need to perhaps consider an overvoltage protection IC or circuit. After that the current draw dropped to about 5-10A (ca. There was a 3ns 6A spike at power on we didn't see with our scope. We'd love to hear your thoughts. An AC6801B AC source can be used to characterize the inrush current of a device quickly, helping you design a device with inrush current that you and your customers can trust. Figure 9. A good strategy to follow in such cases, is to estimate the current at which either the power supply, or some malfunctioning part of your device, is likely to suffer damage. Using the resistor on the positive rail is known as a high-side shunt resistor. Read this blog to learn more about how to use an oscilloscope to measure current. Inrush current is measured as a peak current and is useful for sizing fuses or designing additional protection circuitry. www.tektronix.com/accessories7 Inrush current can only be measured by meters that have an inrush button. Resistor measured 9.7 ohms +resistance of connecting leads + amplifier output impedance. Which one is more appropriate to capture inrush current at 5A instantaneous peak? I'll explain the two methods to measure inrush current using oscilloscopes in detail. Each subsequent measurement uses a 10-degree higher turn-on phase. you cannot measure current simply using an oscilloscope and the normal (voltage) probes. Using an NTC to reduce the inrush current into capacitive device. Figure 3. Consequences resulting from Yitang Zhang's latest claimed results on Landau-Siegel zeros. That would be like trying to measure current with a volt-meter. 1A with the NTC) while the FC and ESCs booted. Only meters that offer an inrush button can measure inrush current. You need to use two probes for doing this measurement and subtract the value of one from the other - DO NOT CONNECT THE GND OF THE PROBE TO EITHER SIDE OF THE RESISTOR- you will in effect cause a short circuit if you do this. I also explain how an electrothermal circuit breaker works by preventing overloads and short circuits. The first one is to add a series resistor to reduce the current flow in the circuit line and the other one is to use line filter impedance in AC supply input. On the meter's face, press the inrush button. Adjust the VOLTS/DIV and TIME/DIV settings until you can see the sine wave. Center the jaw or flexible probe around the device's live wire. Inrush current for a capacitive device, 12 VDC power supply vs. phase. use oscilloscope math capability (or just yourself) to do a difference between the two channels and this will be your current. * Circuit breaker instantaneous tripping current, should it be RMS or peak current?Equipment used:* Agilent / Keysight DSO-X 2000 Oscilloscope* HT Instruments HT9022 Power Clamp Meter* Yokogawa CW10 Power Clamp Meter* Fluke 43B Power Quality Analyzer* Thermal magnetic circuit breakerUseful links:Circuit Breakers - How they Work, What's Inside :https://www.youtube.com/watch?v=u6I7dKDk7hECircuit Breakers:http://en.wikipedia.org/wiki/Circuit_breaker------------------------------------------------------------------------------------------------------My website and forum:- http://www.mjlorton.comDonations and contributions:- http://www.mjlorton.comMy techie channel MJLorton - Solar Power and Electronic Measurement Equipment - http://www.youtube.com/MJLortonMy Techie Amazon Store: http://astore.amazon.com/m0711-20My other channel VBlogMag - For almost any topic under the sun! Here is a quick and dirty method. The meter probe must be clamped around the wire of the tested circuit and the knob must be set appropriately, depending on the current type: AC or DC. Figure 6. Use MathJax to format equations. Configuring the AC source for inrush current measurements is a two-step process. Measuring inrush current is a task that many customers that use DC Power Supplies want to accomplish. Engineering News. To do so, I am using an external power supply in series with a resistor on the external power supply pins, and then using an oscilloscope to measure the voltage across the resistor. Then if you measure the voltage drop across the resistor at power up, with your scope, you will get a fair idea of the inrush current . (My meter isn't that fast, but I do have an analog 100MHz oscilloscope.). Hooking the probes up is series is a sure fire way to blow up your scope. Let us know if you're having trouble or if we're doing an outstanding job. The only sense resistor current probe available . By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Then pick a current between the expected steady state and this estimated overcurrent, and use a PTC of approximately that current rating. I'd like to add a resettable (PPTC) fuse to them but I am not sure what value to select. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. A related, useful question on PTC fuses and low-current applications: Does your scope have a persistance refresh mode (some of the old tek scopes do for example - I have one here) Either that or maybe set up a camera for multiple "sports" type shots (or video) The other option is to work it out using the basic formulas (or simulate it). test the circuit continuity or perform a diode test. The Ohm's law approach is the best option to measure on the A or nA level. We will explore how to use, connect, and choose the right oscilloscope probe for your measurements. Here are steps for measuring it, in this case when using the Fluke 381 (see illustration above): With the device to be tested turned off, turn the meter's dial to . Since all three methods require that the current being measured pass through . 11/13/2008 . Some devices will have to be designed to limit the inrush current. Mostly the voltage is about 15 volts peak but I forgot to bump up the amplifier output as the voltage fell away slightly at high frequencies. Need help on product selection? The devices have a capacitance of about 122F. How to measure current on an oscilloscope ? Have some patience here, some scopes take as long to boot up as an old PC. Small step down transformer fuse, primary or secondary? As the current probe provides 0.1 V/A, the vertical scale in above measurement is 50 A/division. A Free & Open Forum For Electronics Enthusiasts & Professionals, Login with username, password and session length, I came across this graph where current is on the Y axis, YouTube and Website Electronic Resources ------>. Onto the branch of each load, place a Measurement Pr Why are standard frequentist hypotheses so uninteresting? Figure 7. I think I'd try the video/sim options and see how you go there. Normal max. What is this political cartoon by Bob Moran titled "Amnesty" about? You must measure the voltage across a series resistor ("shunt"), or, using something like a current transducer (a torrodial coil or a Hall-effect device). I'm still concerned that the event will be over far more quickly than I can measure. Okay. We are the measurement insight company committed to performance, and compelled by possibilities. All you have to do is to so supply it with some kind of voltage signal that changes over time, and it will display it on the screen. If your inrush current is brief, the PTC does not get enough high-current time to react, before current has settled into steady state. My personal strategy is to simply use a cheap, high input voltage range buck regulator on the input line. In that case, I recommend using a Current Transformer (CT). Measuring inrush current is always interesting. When sampling fast enough you can see that it does indeed take some finite time for the current to rise. A small series resistance (small enough that it doesn't affect the DUT, but big enough that the scope has enough voltage to measure). Is it possible for SQL Server to grant more memory to a query than is available to the instance, Find a completion of the following spaces. Just use a 0.1 ohm shunt resistor, and measure voltage drop across it, do some ohm's law calculation to I = E/R.
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