DIYbanter - View Single Post - Greenlee DC clamp meter, need schematic or cal procedure

spamme0[_2_]

wrote:
On Wed, 22 Jul 2009 12:59:44 -0700, spamme0
wrote:

I have a Greenlee CM-750 DC current clamp meter.
The power-on DC reading is 7.5A.
Yes, the zero button fixes it, but I'd rather have
it power on close to zero. The 7.5A has been VERY
repeatable. I'd be satisfied with equivalent repeatability
at zero.

The thing has nine variable resistors on the current board.
Need to determine which sets the DC offset.
Anybody figured this out?
Or have access to the super-secret documentation?
Or maybe it's equivalent to another brand with
available documentation?

Would save me reverse-engineering the thing.

I did try demagnetizing the clamp with a tape degausser...no effect.

Greenlee support has been useless. They seem to know
what to do, but won't say. "press the zero button"
is about all they'll admit.

Yes, I can send it in and have it tweeked for free...
Problem is that they won't tell me if it will fix the
zero problem..."press the zero button" Grrrrrr!!!!

Help???
Thanks, mike

Was it actually 0 when new?
NO idea, didn't buy it new.

I can see the 7.5 being a model identifier at power on.
Where do you see that?
On mine, it's the amps reading before you press the zero button.

John