Will a 50Hz Meter give false readings for currrent, voltage and watts on a 60Hz supply?

Question

I have a UK combination meter to measure Voltage, Current and Wattage. It is 230V 50Hz appliance used to test household appliances. I'm using it to test Computer equipment power usage.

I need to measure the three metrics on a 230V 60Hz supply. I want to know if the meter will return an inaccurate reading for any of these. I think the Voltage will be fine but not so sure about the current!
Thanks

Answer 1

It depends on what you're actually measuring.

If you're measuring the circuitry inside the computer (i.e. between power transformer and circuit boards, or elements attached to boards), you're reading a DC signal. Effectively, the frequency is zero ... which means it doesn't matter whether the set is geared to 50 or 60 Hz AC operation. You'll get 'true' readings for all DC measurements of voltage, current, and power.

If you're measuring the power transfer from the AC outlet to the computer's power transformer, you might see some errors. It depends on whether the tool is a 'true RMS' meter, or not. A 'true RMS' meter checks the actual signal in very short (high frequency) pulses to average out the results using the RMS method. On the other hand, one that is not a 'true RMS' meter simply checks the peak-to-peak values and multiplies by a hard-wired factor that is dependent on the signal being a real sine wave AND operating at a specific frequency.

The 'true RMS' meter will give you accurate results ... the other will likely give erroneous values for both AC current and AC voltage ... and therefore for AC power.

Answer 2

Most meters first convert AC to DC before displaying results (they display DC values, if you prefer).
Since the rectifier does not really care of the frequency (within certain limits, a few kHz), the readings will be ok.
Current is the same: the AC current passes through a shunt, the voltage across is rectified, then displayed.

Answer 3

If its an old analog meter it won't be accurate, but if its an electronic / digital type it should be OK.