I was given a gift from an estate of a nice looking wattmeter, scaled zero to 120 MEGAWATTS.
That is a lot more power than I intend to work with, so it seems that some scheme should be available to possibly even have multiple ranges, , zero to 12 watts, zero to 120 watts, and zero to 1200 watts. would be perfect for servicing most devices.

The model is listed as " 8AB 18K5 AB1
amps =4 volts =120 C.T.=1400:1, P.T. 120:1
Cal.watts 557 P.T. x C.T.
AND the tag claims it to be 3 phase. Clearly it is not a modern electronic meter, but it looks really cool and a benefit is that it does not need an external power source.
On the back end there are 8 terminals without even identification numbers.
Has anyone ever worked with a meter like this?? Or is it so terribly complex to use that there is no hope for it???

 

Is this an analog meter? If it is it should be possible to rescale it.

Perhaps you can provide a photo?

 

Is this an analog meter? If it is it should be possible to rescale it.

Perhaps you can provide a photo?

WHAT would a photo reveal except the size, which is not small. It has a cylindrical housing, about 3 7/8 inches in diameter and about 6 1/6 inches deep, and a medium shade of grey. The fact that, as I stated, "it does not need an external power source"should tell you it has no digital circuitry at all. The pointer can rotate about 300 degrees, like most of those older GE meters. Internally it has two sets of coils, one on the shaft and one fixed. so the force to move the pointer is the sum of them both. So there are two pairs of coils applying torque to rotate the center shaft to move the pointer.

 

You can scale it down with the ratio of current and potential transformers, all the way down to 557 watts if wired it directly.

 

Good point. Then I still need to fake the three phase power.

 

The pointer can rotate about 300 degrees, like most of those older GE meters

A photo would tell me it's an analogue meter, which you haven't, although that can be inferred from your comments.

 

At a guess the terminals would be L1-L2-L3-N for the current transformers on four of the terminals.
If the meter movements are commoned on N you should be able to find the N terminal by resistance measurement.
Does PT mean “potential transformer” and indicates that the voltage is measured by transformers as well?If so that would explain the other terminals.
As a power meter, it should be able to cope with unequal loading on the phases, so it might work with just one phase connected.

 

@Ian: YES, C.T. is for current transformer and P.T.is for potential transformer. And certainly it is an analog device, very much analog. And god thinking on the three phases not needing to be identical! With what looks like two wattmeter coil sets inside, it evidently is able to do vector math and know what the third phase is doing. Thanks for that suggestion.