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previous: Derrick Back to the problem, I checked the... -- 5/7/1998 9:55 AM

Re: Not your typical bias problem!

5/7/1998 10:45 AM
Doc	Re: Not your typical bias problem! Derrick- Are you certain that the meter you're using for the bias measurements is accurate & calibrated? Many meters don't have accurately calibrated internal currrent shunts. If the current scale is accurate, with your shunt resistance being 1.2 ohms, and the transformers resistance being 16 ohms, what you read will be about 10% lower than what's actually passing through the plate, because of the unmeasured portion still skating around the meter path through the transformer. Now if your meter reads 10% low (not calibrated) on the portion of the scale you're using, you can see there's a problem with using that meter. Can you try taking a shunt reading a with a friend's meter that's a known quantity? Another way to check accuracy is to place both meters in series. They should read the same current. Doc

5/7/1998 10:45 AM

Doc

Re: Not your typical bias problem!

Derrick-

Are you certain that the meter you're using for the bias measurements is accurate & calibrated? Many meters don't have accurately calibrated internal currrent shunts.

If the current scale is accurate, with your shunt resistance being 1.2 ohms, and the transformers resistance being 16 ohms, what you read will be about 10% lower than what's actually passing through the plate, because of the unmeasured portion still skating around the meter path through the transformer. Now if your meter reads 10% low (not calibrated) on the portion of the scale you're using, you can see there's a problem with using that meter.

Can you try taking a shunt reading a with a friend's meter that's a known quantity? Another way to check accuracy is to place both meters in series. They should read the same current.

Doc

Replies:

HM Doc is that meter you have a dedica... -- 5/8/1998 6:00 AM
Derrick As of now, I have two areas to chec... -- 5/8/1998 10:36 AM