Author Topic: Fluke 87V "bricked" when probing own battery  (Read 5894 times)

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Offline Z-mann

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Fluke 87V "bricked" when probing own battery
« on: May 19, 2014, 10:16:49 pm »
I discovered the following thing:
When you touch (accidentally!) the positive terminal of the 9V Battery, with the COM lead in VDC Mode - the meter will reset and shows "bAtt" continuously.

I think the Batt.-Voltage detection has failed.

Of course the Battery is full and the fuses are fine.

I downloaded the service manual, and I'm currently looking for a voltage divider (or similar) for measuring the Vbat.
I would appreciate some advice or a hint to look for, in the schematics.

Greetings  :-BROKE
 

Offline NANDBlog

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Re: Fluke 87V "bricked" when probing own battery
« Reply #1 on: May 19, 2014, 10:41:59 pm »
Every manual states: Remove probes when opening. No probes, no measuring battery. I don't know why you would even try??? It has low battery indicator for you.
 

Offline retrolefty

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Re: Fluke 87V "bricked" when probing own battery
« Reply #2 on: May 19, 2014, 11:59:52 pm »
Every manual states: Remove probes when opening. No probes, no measuring battery. I don't know why you would even try??? It has low battery indicator for you.

Come on he said "(accidentally!)". The question is it recoverable or did it cause some component damage?

 

Offline FrankenPC

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Re: Fluke 87V "bricked" when probing own battery
« Reply #3 on: May 20, 2014, 12:14:23 am »
Every manual states: Remove probes when opening. No probes, no measuring battery. I don't know why you would even try??? It has low battery indicator for you.

I honestly didn't know that.  I do now though.  Thanks for the valuable lesson bricked Fluke guy!

NOTE:  In the 25 years I've been using DMM's, I've never used the meter on it's own internals.  Just for the record.
Chinglish poetry: In the hot summer. In the car ran full steam. It tastes strange. For this worry? With this fan will bring you a cool summer. Suitable for all kinds of cars. Agricultural vehicles. Van. Tricycle.
 

Offline Napalm2002

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Re: Fluke 87V "bricked" when probing own battery
« Reply #4 on: May 20, 2014, 12:24:56 am »
It's the whole don't push that button thing. You know u wanna!
 

Offline DJ

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Re: Fluke 87V "bricked" when probing own battery
« Reply #5 on: May 20, 2014, 01:47:09 am »
 

Offline echen1024

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I'm not saying we should kill all stupid people. I'm just saying that we should remove all product safety labels and let natural selection do its work.

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Offline John Coloccia

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Re: Fluke 87V "bricked" when probing own battery
« Reply #7 on: May 20, 2014, 03:04:20 am »
Did you try removing the battery and putting it back in?  They could just be using a comparator, and some of them are very low current draw (just a few microamps) so it might just be on all the time, even when the meter is "off".  This would also typically include some sort of hysteresis setting so it doesn't continuously trip on and off around the threshold.  That could be set very wide, and now you're just stuck in low battery mode until you completely remove it and pop it back in.

Just a thought before you start tearing stuff apart.
 

Offline Z-mann

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Re: Fluke 87V "bricked" when probing own battery
« Reply #8 on: May 20, 2014, 08:36:43 am »
Every manual states: Remove probes when opening. No probes, no measuring battery. I don't know why you would even try??? It has low battery indicator for you.

Come on he said "(accidentally!)". The question is it recoverable or did it cause some component damage?

Yea my fault, NANDBlog you're right, the manual says exactly this steps.
Anyway, I left the battery out for 20 minutes with the meter turned on (discharge). Still no luck.
I think some components are damaged.

Of course the meter will be fine, but the meter won't operate when thy ┬ÁC detects a low battery.

 

Offline eurofox

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Re: Fluke 87V "bricked" when probing own battery
« Reply #9 on: May 20, 2014, 08:57:05 am »
I discovered the following thing:
When you touch (accidentally!) the positive terminal of the 9V Battery, with the COM lead in VDC Mode - the meter will reset and shows "bAtt" continuously.

I think the Batt.-Voltage detection has failed.

Of course the Battery is full and the fuses are fine.

I downloaded the service manual, and I'm currently looking for a voltage divider (or similar) for measuring the Vbat.
I would appreciate some advice or a hint to look for, in the schematics.

Greetings  :-BROKE

This is an instrument suicide (Latin suicidium, from sui caedere, "to kill oneself")  :-DD :-DD :-DD :-DD :-DD
eurofox
 

Offline han

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Re: Fluke 87V "bricked" when probing own battery
« Reply #10 on: May 20, 2014, 09:31:13 am »
is warranty still cover it?


if not, see page 2-9
at:
http://assets.fluke.com/manuals/83_85_87smeng0500.pdf


you can check the component mentioned
good luck  ;D
 

Offline NANDBlog

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Re: Fluke 87V "bricked" when probing own battery
« Reply #11 on: May 21, 2014, 11:44:01 am »
Every manual states: Remove probes when opening. No probes, no measuring battery. I don't know why you would even try??? It has low battery indicator for you.

Come on he said "(accidentally!)". The question is it recoverable or did it cause some component damage?

Yes, that is true. Sorry, I thought he actually wanted to measure the battery by the very same multimeter.
Anyway, it is highly possible, that they keep the positive terminal at a certain voltage, compared to the battery terminal. In such case if there is an active component doing this, that is probably fried.
 

Offline saturation

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Re: Fluke 87V "bricked" when probing own battery
« Reply #12 on: May 21, 2014, 06:23:12 pm »
This is the first I've heard of this issue on this forum.

Most good DMM power supplies are isolated from its measurement circuitry.  To illustrate, see the Fluke 87-I regulator section in the schematic linked.  Thus, the input section floats relative to the 9v supply.  Probing the battery on any DMM with its own probes even with proper polarity should not be done, not just on Flukes.

Note, you can get old DMMs and some modern panel meters that have common ground with it its power supply, such as the negative terminal of a 9V battery.

What to do now?  The manual of the 87 can be illustrative but it may not be relevant to the details of the 87V as its 4 versions old.

I'd suggest trying any of the following procedures as you've nothing to lose, on the assumption its not physically damaged, try it one at a time and see what happens:

Remove the 9v battery, and short the 9v inputs assuming waiting 20 min with battery removed was not long enough

On the service manual of the 87V, do all the performance check tests, the LCD, the fuses, etc., see if will reset the battery annunciator.  Also, you'd like to know if the DMM is actually truly working right.  The hope is that when in 'test' mode the firmware executes some form of full reset before executing the test sequence and could reset the battery reference indicator.

If the above doesn't work, engage the calibration mode, then abort it.

If the above doesn't work, reset the security password for calibration to "1234".

All the above assume that the firmware will begin any test sequences with a full reset, a function that isn't available directly through another user control.

Keep us posted.


Best Wishes,

 Saturation
 

Offline SeanB

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Re: Fluke 87V "bricked" when probing own battery
« Reply #13 on: May 21, 2014, 07:06:59 pm »
If you are lucky all you did was cook the power switch fet, otherwise you have damaged part of the meter asic itself, and that is not repairable. On the diagram above that would be Q3 or Q8.

Next time if you really want to measure battery voltage, measure using the positive lead only with the meter in manual range, and add the 2 voltages together.
 


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