# How can I measure high voltage?

How can I measure high voltage?

Voltage measurement range: -150 to 150 [V]

1. How to measure through voltage distribution (using resistors)
2. Other methods

Help me.

1. Use a voltage divider to measure positive voltages. Standard values 270K and 9.1K will give you a division ratio of 31, to reduce 150 V to 4.84V. Don't forget to connect the grounds.

2. Multimeter

myksj12:
How can I measure high voltage?

Voltage measurement range: -150 to 150 [V]

1. How to measure through voltage distribution (using resistors)
2. Other methods

Help me.

What accuracy are you looking for? AC or DC?

myksj12:

1. How to measure through voltage distribution (using resistors)
2. Other methods

Other methods: electroscope for DC, capacitive dropper for AC.

The voltages you are talking about can be lethal, never forget that.

Better reduce the voltage to measure to <1V and use the internal reference. Will give more stable measurements. That’d require a 1:300 divider for the full range, and possibly some resistors for an appropriate offset so 0V comes to 0.5V, -150V to just above 0V and 150V to about 1V.

In addition to a [u]voltage divider[/u] it's a good idea to add an [u]over-voltage protection circuit[/u]. All multimeters & oscilloscopes have protection so you don't fry the meter if you connect to a high voltage while on a low-voltage range. (Although you can still fry stuff when reading current with a meter. )

If you are measuring AC, remember that you are "sampling" a constantly-changing wave. You can either find/measure the peaks, take an average of the absolute values, average the positive values (and ignore the negative values), or directly calculate the RMS.

For sine waves there is a known relationship between peak & RMS or average & RMS. For other/arbitrary waveforms you'll need to make a true-RMS calculation if you want to know the true RMS value. (Most multimeters are "calibrated" for sine waves only. Meters that measure true RMS are more expensive.)

The Arduino can't read negative voltages (relative to it's ground). If you have a floating/isolated power supply (or a battery ) for the Arduino, you an reverse the connections to read the negative voltage. For AC, you can bias the input and then subtract-out the bias in software.