Mesuring High voltage (500V)

You don't say if it's ac or dc.
If AC you could of course use a transformer.
If it's DC you could maybe chop it and use a transformer.
Or use it to drive an opto coupler and measure the shift in output, you'd need precision resistor to limit the current of course.

For more ideas please insert another coin or send tuna.
Del

soory it is DC voltage

Any particular reason why you don't want to use a simple resistor divider? I think you'll find any other solution will be more complex & expensive, and no more accurate.

Thanks friend

God bless.

A simple voltage divider will likely be your best bet to step down these voltages to a usable range for your A/D card. But you leave out a lot of critical information to design a suitable divider network.

• What is the input impedance of your A/D card?
• What is the anticipated source impedance?
• How accurate do your measurements need to be?
• How much resolution does your measurement require?
• How noisy of an environment will this be?

That's all that I can think of for now, but I'm certain I forgot something.

Another solution is to use an electrometer amplifier with a very large value input resistor in a current to voltage converter configuration. This way you do not have to deal with a divider arrangement and a very high value input resistor can be used. Analog Devices makes some good electrometer amps or even a very high input impedance op-amp can be used if configured correctly.

Adding any active component will always add additional error sources. If you don't know how accurate the measurement has to be or the resolution required then you cannot say that the errors will not be significant.

Yes you state what is very obvious. The basic request was for alternative methods which is the suggestion fulfills. Whether it is suitable for the particular application we must leave to the person with all the details. In my answers I assume the asker to be capable of evaluating the suitability of the response. I don't have time to second guess all the possible unknowns.

I would use your voltage divider with good quality resistors (look into wire wround) that are not to sensitive to temperature changes since this changes resistance. Then I would use a 10 turn high quality pot to balance trim +- say 2%. This will allow for temperature changes and tolerances in the voltage divider and therefore you can trim to 0% or as close as possible. Calibrate as needed.

A company by the name of Caddock makes precision voltage divider networks that are used in many of the high-end voltage sensing applications (voltmeters, etc.). The multiple taps of the resistor network correspond to the different ranges on the voltmeter. Please see their website for more information, the link below is to the product page for their precision divider networks.

Caddock Resistors

Hope that helps,

Tom

The OP doesn't define "good accuracy". Please define that. If it is within 1%, I also vote for a simple voltage divider. If it is higher than this, then you can still use a "trimmed" voltage divider as mentioned by others. At 500V you can get and choose components that will not vary much due to temperature and/or voltage. Don't make things more complicated than is necessary.

Use a high voltage probe. Here is a URL for a Tektronix P5100 (about $ 400 list).

http://www2.tek.com/cmswpt/psdetails.lotr?ct=PS&ci=13471&cs=psu&lc=EN