Percentage of Error in Analog Meter Readings

In my opinion, having worked for GE Meter DPT. for some years ( although I am not an EE), is that good quality analog (or mechanical) meters are just as accurate as modern solid state meters provided that they have been properly calibrated. The switch to digital meters was motivated by lower manufacturing cost, not by any improvement in accuracy.

If there is significant discrepancy between the service entry meter and the sub meters, there is most likely a problem in the building's electrical system.

There will be no error in any of the meters. The power usage fees will precisely reflect the readings of these meters. It is customary to also include some fixed added offset fee for providing the wiring infrastructure when totalling the fee. These meters and only these meters will be the basis for the additional kilowatt hour fee. If you take any other opinion or perspective you will be setting yourself up for many arguments. Keep it simple.

Mr. Redfred, Analog or digital, there will always be a tolerance, and % of error associated in any of those meters. In usage, we analyze each type or model make a decision, then select which one is more acceptable for any given application, analog or otherwise. Sensitivity of the movement in a mechanical meter is a good example and in digital, the technique, sampling technique used in digitizing the analog information also affects the reading accuracies of such devices. Age of the mechanical device may also be a contributing factor for such accuracy. Thank you, VSAR - NYC

Oh I very much know that all measurement devices have linear and non-linear error tolerances. But without knowing anything about the model numbers, how many digits each model displayed, or how much power usage each meter was recording in a month I knew that any answer I provided on an analog or digital meter would be a completely uneducated guess. You are also quite correct though that mechanical wear and tear will likely increase the tolerance in an old meter. I did a little extrapolation on why the question was being asked here at a public forum by somebody not employed by the power distribution company. (An employee would be able to simply look up the meter's expected tolerances from the unstated model numbers.)

Since any answer would then require a guess on the equipment, I decided to guess why the question was being asked instead. I guessed that the root question was why the service provider's usage bill did not agree with the anticipated usage. In making my leap to this other question, I also considered that even an old worn meter would not have even a 5% error. This small of an error would likely not even be noticed. At the time I felt that the OP was only considering that the meters were recording incorrect power usage and wanted to know the errors to explain a billing discrepancy. I then tried to explain that these meters are the basis for the utility to establish the bills, not any other method of testing the OP may come up with. I particularly wanted to point out that a zero power usage would not result in no bill for anyone because the utility was still providing the value of power being available at the flip of a switch.

I also hoped that the OP would respond to my tangent by providing some more details so that somebody could accurately answer the real question that is making a problem.

Oh - ok, I missed reading between your lines. Thanks.

just quickly do the total sum of the sub-meter and compare to your digital meter and see if there is any difference. If there is then work backward with your meters (amp and volt) to work out which % error of each sub meter.

The reading error of an analog meter is usualy written on the scale itself,

in the lower riight edge usually you can see some symbols, these are the informations about the meter,

Full sacle error, type, class.etc.....

Well the error of actual consumption and shown reading will be sum of percentage errors of main meter and submeter

the %55555age error is called accuracy class and its always mentioned on meter inside dial or else where like

class 0.5, class 1 or class 2 means 0.5%, 1% and 2 % if u have CTs in circuit the error may increase more

how ever diorect meters the error will not be more

In anlogue energy meters,accuracy class is indicated in the meter name plate/ dial; from the above one can understand the percentage error( viz. for accu. class of 0.5%, percentage error is +/- 0.5% on full load condition.). If the meter is CT operated, CT error should be added. Also it is to be noted that energymeter registers energy consuption of LOAD in which it is connected i.e. it is measuring energy consuption ( Power*Time) of the circuit it is connected. It will not register energy consuption of incoming circuit. Therefore, it is verymuch important that location of submeters from main incomer meter for comparing energy consuption data. For better result, it should be very close vicinity of main incomer meter

the analog meter is hardly 1meter apart from the digital meter.

the difference in reading between digital and analog meters are almost 25-30%.

digital and analog meters are CT operated

regards

salahuddin zia

Well at least we now have a little more information to work with. I don't mind playing twenty questions, but only if you answer our questions. Let me restart with with a few questions.

What is a sample set of power usage readings that prompts your question? Don't give us your analysis results without the raw data because we won't be able to tell if your data or analysis maybe the problem.

Speaking of raw data, maybe your primary meter has been scaled to handle the expected larger draw of being the primary meter and reporting the power of the other three meters combined. Are you certain of the raw data numbers?

Lastly (for me) are you certain that the three analog meters are not running off of a separate feed from downstream of the digital meter? It doesn't make sense to me that your utility provider would configure these meters with a primary feed meter. Each meter produces a bill somewhere. By having the same power run through two meters, they're double dipping.

The error will be composed of the error of the metering system. The system is composed of the error of the :

1. Meter Error

2. Instrument transformer error if instrument transformers are used

3. The error introduced in the interpretation on the analog dial or dials

The meter should be tested initially to determine the as found error and tested every three years to verify the accuracy.

The system error would be the square root of the sum of the square of the individual errors. The individual errors would the meter error and the error of the instrument transformers.

Dear Salladdin
Dear participants and all
Read the responses and discussion, but I have not an idea I intended to ask
My question is to Mr. Sallah:
Is your circuit is among the three phase digital meter, series with three single phase meter?
Or is it otherwise?
In this case if it include a capacitor in the circuit ( if it has a damage in 1 ph. Of it ) then the phasor diagram will be not correct. Then the cos of angle will differ and value of the consumed energy in the meters is different ( to less or up ) as COS value.

You will find that one of them to score high , the second exact and the third register is set inverse( stop if has reverse brake ) .
The first meter is not affected ( it has one disc ).
This make a difference between the total meter readings of the three single-phase meter reading and the three phase meter ( the main one ).at least the reading of the three single ph meters will be more than that of the 3 ph meter.
I hope I have brought the information.
And excuse me if I have error in writing or Translation
Thank you
Engineer Saad