High voltage measurent

[umesh49]

Hi;
I need to measure an transient voltage in the range of 2kV - 4KV.
This is the voltage actually an inductive coils generates for very short time when the switch got open. We did not use an freewheeling.
so is there any way to measure this voltage. I am not concerned about accuracy but looking for some hardware/probe with the help of which I can see it in real time in Scope.

Thanks in Advance for your help.

Regards,
Umesh

 

[FvM]

Usually the voltage range will be handled by a 100:1 passive probe, available from oscilloscope and accessory equipment manufacturers. If you want to measure AC only, a simple capacitive voltage divider might serve your application. You should have an idea about the source impedance and acceptable probe capacitance.

 

[mtwieg]

What kind of bandwidth do you need, and what kind of money do you have to spend?

 

[umesh49]

Actually, it is a transient impulse voltage. I am looking for some solution within $100. I have all the high end scopes in our lab but looking for some circuit/probe to interface with it. I can design some circuit, but it is high voltage and I dont want to have a risk situation due to my in-experience with high voltage design.
Regarding bandwidth, it is a pulse which will rise from 30V to 2K within 50usec and drop to zero in 50msec.

 

[mtwieg]

For a 50us rise time you can get away with a resistive attenuator. Just find a good pulse-withstanding resistor in the range of 1-10Mohm (or use a series string of normal resistors), use it in a resistor divider, and just connect that right to your normal scope probe.

 

[chuckey]

I think that with a CRO input capacity of 50 PF, which is typical and ignores any connecting cable, the resistive attenuator should be compensated, unless the bottom resistor is less then 10K.
Frank

 

[WimRFP]

I would also go for the resistive divider with about 1 k parallel with the input of the oscilloscope (so don't use a 1:10 probe). As mtwieg suggests, a series circuit of resistors would be OK. Compensation is very likely not requried.

When your want 400 mV output with 4 kV input, you need a division ratio of 10k. So the series resistance should be 10 Mohms (using 1k parallel to the input of your oscilloscope).

About 21, 470k resistors (just use leaded types) will do the job. If you have a pulse generator available with relatively large output, you could have just enough output voltage to measure the flatness of your home made probe (you may need averaging function on the oscilloscope to reduce noise).

If your application needs more then 10 MOhm, you may reduce the output voltage to say 40 mV. Make sure that your (plastic) support for the resistors is clean before assembling/using your probe.

 

[avrilcory]

There is develops and manufactures high voltage probes which define the state of the art in high voltage measurements. Riello-ups also develop and manufacture support circuits for closing tubes including Thyratrons and Ignitrons at affordable prices in a national laboratory.


Thanks