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| Cheap 100:1 2KV Oscilloscope probes - any experience ? |
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| David Hess:
They work fine however be aware that they cannot be used safely at high voltages with AC coupling. If a x100 probe has a 100 megohm input resistance which is all of the common inexpensive ones, then it has 99 megohms in series with the oscilloscope's input resistance of 1 megohms. But when the oscilloscope's AC coupling capacitor is included, the capacitor will charge to the voltage at the probe's tip and the input voltage rating of the oscilloscope will be exceeded by several times causing high voltage breakdown in the oscilloscope possibly damaging it. Better x100 probes have a shunt resistor preventing this problem and can be identified by a lower input resistance specification. |
| Miyuki:
--- Quote from: David Hess on March 22, 2017, 08:16:20 pm ---They work fine however be aware that they cannot be used safely at high voltages with AC coupling. --- End quote --- Oh that is important info thanks :-+ So I ordered two Hantek T3100 |
| ziakansi:
Hello Folks I found this discussion quite useful. I am using T3100 Probes. Since, it is 100:1, so it should attenuate the voltage by the factor of 100. However, in my case it does not perform attenuation and gives me output as 1:1. I ordered four probes and all has the same output. Am I missing something here? Please guide me how can we get the correct attenuation. |
| wasedadoc:
--- Quote from: ziakansi on March 11, 2024, 11:47:31 am ---Hello Folks I found this discussion quite useful. I am using T3100 Probes. Since, it is 100:1, so it should attenuate the voltage by the factor of 100. However, in my case it does not perform attenuation and gives me output as 1:1. I ordered four probes and all has the same output. Am I missing something here? Please guide me how can we get the correct attenuation. --- End quote --- Sounds like you are missing the required 1 MOhm "load" on the probe output. What are you connecting the probe to? |
| G-son:
--- Quote from: amspire on March 20, 2017, 11:36:57 am ---...you have to look carefully at the voltage derating. At 1500V, the maximum frequency is 2MHz. At 20MHz to 100MHz, the maximum voltage is about 400V. If you are talking about a waveform with a lot of transients or noise, there may be a significant high frequency component. --- End quote --- I read somewhere that this derating is because the current flow through the capacitance of the probe cause a significant power loss = heat in the probe at high frequency. Is that the only issue? I'm thinking if it's only heat we're worried about we should be able to more or less ignore the derating if we only get short high frequency, high voltage transients, with plenty of cooldown time between - but things tend to be more complicated than they seem so it might not be that simple. |
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