Anyone know a DVM exorcist?

I have an old original Fluke 87 that did that. It turned out that the switch rotor had got chipped, allowing the switch to rotate just a bit past the "Off" position.

Cheers

Phil Hobbs

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s a

Now THAT's dedication, sleeping with your DVM. ;)

and

never with my Fluke 77 but did have it with a SOAR 3210 DVM with low battery

Sorry. I meant annunciator. Ouch.

Uh... It was on the floor. Next to the bed. Really.

My Fluke 77 does that when the 9V battery is not quite totally dead.

Yep. You'll also find that it gives wrong voltage readings with a low battery. The irritating part is that it will give bogus readings long before the battery is obviously dead.

Jeff Liebermann wrote in news: snipped-for-privacy@4ax.com:

doesn't it have a LOW-BATT indicator on the LCD screen?

To avoid the incorrect readings, use alkaline batteries. The meter will remian more accurate for longer this way.

Yes, the Fluke 77 has a low pattery indicator. I have found that the unit gets a bit unstable before that indicator comes on. I check the battery regularly to prevent this. I don't rely on the low battery indicator.

Dan

Yes. The Fluke 77 has a rectangular battery symbol in the upper left corner of the screen. When it comes on, the battery is certainly dead. However, voltage measurements go insane somewhat before the indicator comes on. I was checking my supply of AA alkalines in the fridge and noticed that I was tossing far too many batteries as dead. I checked the readings with another DVM and found that the Fluke 77 was erratically reading about 300mv low. The battery indicator never came on. When I replaced the battery, the readings returned to normal. I don't recall if the flashing display happened before or after the battery indicator.

That was with an alkaline 9V battery. I'm tempted to spend the $7.00 and get a "smoke alarm" lithium battery such as an Ultralife:

You mean useless. If it were dead...

This is Most Amusing, because I was checking a pile of NiMH AA cells, and most of them read a few tenths of a volt. Then, a few hours later, they were all fine.

In case you're wondering... Of course I use an alkaline battery. A lithium would be an even better choice. MCM has name-brand lithium 9V batteries for about $5 right now.

Can you calibrate the Battery Low feature? One would think so...

John :-#)#

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FWIW, I had two 87s (early type) die slowly, and in the same manner. It started out with the beeper making various noises for no reason. In both units, I opened up the case and disabled the sounder with some cellophane tape between the sounder and the main board. Later, they became flakey and eventually stopped completely. My 77, which has outlasted two 87s, is bulletproof, but doesn't have the features, speed, resolution, or immunity to noisy situations, like reading dc voltages in flyback\smps circuits that the 87s have.

John

Could it be just the function switch is flaky and needs cleaning?

Mark Z.

Don't think so. You can see where the missing chunk allowed the rotor to go about 60 or 80 mils past the "off" position, and preventing this fixed the problem.

Cheers

Phil Hobbs

It's a common design problem. How does one provide an active indication that the power source is dead, when the indicator is powered by the same power source. The usual "solution" is to have the indicator proclaim a dead battery, long before the device ceases to function. My HP calculators mostly do it that way. I can run them for months with the dead battery indicator showing.

Ummm... I don't think that's the result of a low battery in your Fluke

1. My 77 is similar and simply produces modest errors before it quits completely. A few tenths of a volt is a rather drastic error. Check the probes?

Cool. I need some other parts from MCM. Thanks.

Calibrate? Methinks not. There no adjustments.

I got lazy and tried to measure the battery voltage using the voltmeter. I suppose I could install a switch to do that automatically and call it a "battery test" function.

I have an analog battery tester that puts a small load on the battery when measuring. It works much better than any open circuit measurement. However, I can never seem to find it when I need it.

What about adding a terminal or test point somewhere on the case that connects to the positive terminal on your battery? On my cheap (but remarkedly durable after ten years of being dropped) meter the readings I get on the battery positive terminal are 3.06 (using the red + probe) and -6.03 (with the black - probe) this shows a battery of 9.09VDC charge.

My meter did not like my using the negative probe on the negative terminal of the battery - it buzzed at me!

John :-#)#