Real Power Calculation on Omnimeter II UL v.3

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thill7881
Posts: 1
Joined: Wed Dec 15, 2021 2:13 pm

Real Power Calculation on Omnimeter II UL v.3

Post by thill7881 »

Hello EKM Support,

I am attempting to perform power consumption analysis on several products. Specifically i am looking at a 120V , two-wire, single-phase device, powering two electric motors. I am measuring the power using a Omnimeter II UL v.3.

My question is how is your reported "RMS_Watts" value calculated internally? Based off of the recorded current, voltage, and power factor my hand calculation of what expected Watts should be does not match the value reported by the meter. I've attached a screenshot of some example data.
Whether my calculations are incorrect or if there are some other variables i am not accounting for, any insight would be greatly appreciated!

Thanks,
Thomas
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Jameson
Posts: 812
Joined: Fri Nov 04, 2011 7:42 pm
Location: Santa Cruz, CA
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Re: Real Power Calculation on Omnimeter II UL v.3

Post by Jameson »

Hello Thomas,

Yes, the Omnimeter uses this formula to calculate watts and kWh internally on each phase:

Volts x amps x power factor = watts

In your top row that would be 117.7 x 7.4 x 0.74 = 642.9 watts

Im sorry if this is an unsatisfactory answer, but the calculated watts does not often come out to the reported watts, this has to do with how the metering chip reports each of these values and that each of the values comes from an different instance in time). We do stand behind the reported kWh being accurate.

I hope this helps.
Jameson
EKM METERING
http://www.ekmmetering.com
831.425.7371
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