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Fluke 800A bench multimeter: normal behaviour or defect?

G'day,

I've recently acquired an old bench multimeter, a Fluke 800A.

On the most sensitive AC-range (200mV AC) it seems to 'overflow' (displaying 1999mV) when leads are attached. Is this normal behaviour for this equipment? When shorting the leads, it displays correctly. On the 2V AC range, it displays about 0.3VAC...

Is this because of RF interference in the air (but why don't my other multimeters have it so badly?) or is it in need of repair?

If it's repair that's needed, any idea where to start looking? Or, does anyone have a schematic or service manual available for this Fluke

800A?

Sincerely,

Peter, The Netherlands.

Reply to
peter_dingemans
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If you mean just hanging not connected to anything, it's probably normal. If it zeros when they are shorted, then it's likely working.

Measure something to confirm.

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Reply to
Sam Goldwasser

With the leads hanging in the air, being unterminated, it is normal that the instrument will pick up some voltage, or AC radiation from the surrounding environment, such as from the wiring in the walls, and etc. The 200 mv scale is very sensitive.

The proper way to test this is if the leads are shorted, and the meter zeros, indicates that the meter is able to be referenced.

The second part of the basic test is to have a known proper calibrated AC voltage source that is in the 200 mv range, to see if the meter is accurate.

Jerry G. ======

Reply to
Jerry G.

Thanks, Sam and Jerry.

Will give it a try with a (more or less accurate :-) ) mv AC-source. All the other ranges work fine, as far as I can tell, only the mV AC range overflowed. Strange that none of my other multimeters show this behaviour (or at least much less; about 30-40mV on the 200mV range).

All that's left to do is find some good testleads for this Fluke, and it'll be ready for everyday use.

Grtz,

Peter PE1VCC

Reply to
peter_dingemans

The 8000A was designed before anyone cared about RFI to instruments. It has a very sensitive front end and an A/D conversion scheme that is susceptible to rfi.

The cool thing about the 8000A is that is uses calibrated current sources to measure ohms. It has 200mV and 2V basic ranges and the currents are adjusted to give the right full scale range. For example, the 2k range puts out 1ma. Fluke later featured this range and called it diode test on the newer instruments. You can push in both the current buttons and the ohms buttons to measure your current.

Makes a nice little current source for match>Thanks, Sam and Jerry.

--
Steven D. Swift, novatech@eskimo.com, http://www.novatech-instr.com
NOVATECH INSTRUMENTS, INC.      P.O. Box 55997
206.301.8986, fax 206.363.4367  Seattle, Washington 98155 USA
Reply to
Steven Swift

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