any good substitution for 845AB?

[goodpass71]

Does anyone know any good substitution for Fluke 845AB Null Detector?

[CalLabSolutions]

I think Tegam has a replacement meter.

Also, the HP 3458A (And Several other Meters) have a null measurement function.

Mike.

[beadwork]

Check out Fluke article "Self‐Calibration of the Fluke 752A Reference Divider using the Fluke 8508A Reference DMM in place of the Fluke 845A Null Detector".

I would not recommend getting the Tegam AVM-2000 Null Meter.

[rjf1957]

Do you have a link to that? I can't seem to find it.

[sdmetrol]

I agree with beadwork,  we have shifted that workload to a Fluke 8508A Reference Multi-meter as well.

This link has many great resources, you will see the articles you require listed under Electrical Calibrations http://us.flukecal.com/category/literature-type/articles-and-education.

[measure]

Check out Fluke article "Self‐Calibration of the Fluke 752A Reference Divider using the Fluke 8508A Reference DMM in place of the Fluke 845A Null Detector".

I would not recommend getting the Tegam AVM-2000 Null Meter.

The idea of using any digital multimeter (DMM) as a null detector is flawed by the fact that DMMs contribute input bias current and pump-out noise to the measurement, not to mention how frustrating it can be attempting to null a manual device, such as a Fluke 752A, while watching the digital readout bounce around like a ping-pong ball. The Fluke application note mentioned is a good one, but merely offers users a band-aid workaround when what the industry really needs is a good, decent null detector.

I have no specific idea what the poster meant by his comments regarding the Tegam AVM-2000, but would add that in my limited experience with same, I found it somewhat trying when attempting to use it to perform the 752A Self-Calibration routine.

[Pylarinos]

Hi I have used the 3458A in a differencial mode with excellent results.

[scottbp]

In a pinch, I've used a HP 34420A nanovolt meter in place of an analog null meter, though I have heard from others that a Keithley 2182A works better for this application...

[Squidley]

The AVM-2000 is about as rugged and reliable as a wet matchbox... Everyone I have ever worked with failed.

[yonker08]

The AVM-2000 is about as rugged and reliable as a wet matchbox... Everyone I have ever worked with failed.

RUN..., don't walk away from them!

[Karl]

34420A works but you have to do a coarse and fine setup
as you get towards a null. We use it with metcal to capture the readings from the 752A
cal.
Karl

[measure]

Karl, believe me or not, but if you're using a 34420A as a detector with a Fluke 752A, your not getting the true picture (I'm in a position to know!). The 752A MUST work into a high impedance, and the 34420A, along with some other design oversights, does not satisfy that requirement. If you don't believe me, borrow a good working Fluke 845AB (if you can find one) and make comparative measurements. I'm certain you'll find differences, especially on the 100:1 ratio and in varying amounts, based on the individual characteristics of the 34420A. Trust the readings from the 845AB and shuck the rest.

[Ex-Navy]

My Fluke 845AR randomly wanders approximately +/- 1/4 microvolt on the most sensitive ranges.  This happens with the meter in either zero or operate mode.  I suspect this is a common problem.  Has anyone heard of an effective fix?

Thanks,
Joe

[CalLabSolutions]

Ex-Navy,
My first thought is Thermoelectric Voltages.

http://www.callabmag.com/?p=2180

[USMC kalibrater]

Better cables and connections