[Amps] Volt-watt meter

[Gary Schafer]

What is full scale power of the meter?

You could use a precision resistor in series with the load and measure 
the voltage across the resistor to get current. However keep in mind 
that most ac voltmeters don't do a very good job. If you get with in a 
few percent you will be doing good.

73
Gary  K4FMX


Will Matney wrote:
> I have a Simpson volt-watt meter here I'm thinking about getting calibrated. The thing is, I'm not really sure how accurate it is. After I bought it, I tried it out on a lamp in the house using a 100 watt buld. Something didn't jive about the watt reading when I calculated the wattage from the line voltage shown as the meter showed a lower wattage. I wonder just how accurate those bulb ratings are? Simpson is known for good accuracy because of their meter movements, but I'm not too sure about this. I'd like to test it again before I pay a fortune for calibration on it. I thought of using a transformer but then your not sure what the power actually is due to losses. I don't have any power resistors large enough handy to at least get a 1/2 scale reading. What might be a good circuit I'm not thinking of to test this? Note; this meter is designed for power readings on a 120 or 240 Vac line.
> 
> Thanks,
> 
> Will
> 
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