Multimeter won't zero, only on DC volts
 

(WbSearch) writes:

Have a Micronta M/N 22-191 multimeter that recently won't display zero only on
DC at the 2 volt selection or higher. The 200 mv scale is fine, as are all
scales of AC volts. The display shows between 0.100 - 0.500 volts, even when
the plus and minus leads are touched together. I have cleaned the PCB and
switches which helped for a short time. All diodes, resistors, batteries and
fuses check fine. All other functions work properly as well. Any other help
is appreciated.
Also, does anyone know what the 2 POT's are for? The manual doesn't go into
that detail. Thanks in advance.

In any case, a sudden change in behavior isn't an adjustment.

I also have a DMM that reads slightly off 0 on just 2 or 3 ranges but is
otherwise accurate.

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Multimeter won't zero, only on DC volts
 

I didn't mean to imply I was going to mess with the POT's. I did find in the
manual they are to calibrate the DC and AC volts. So I assume they are OK and
haven't/won't change them. I agree something else is happening.

Multimeter won't zero, only on DC volts
 

"WbSearch" wrote in message
...
Have a Micronta M/N 22-191 multimeter that recently won't display zero
only on
DC at the 2 volt selection or higher. The 200 mv scale is fine, as are all
scales of AC volts. The display shows between 0.100 - 0.500 volts, even
when
the plus and minus leads are touched together. I have cleaned the PCB and
switches which helped for a short time. All diodes, resistors, batteries
and
fuses check fine. All other functions work porperly as well. Any other
help
is appreciated.
Also, does anyone know what the 2 POT's are for? The manual doesn't go
into
that detail. Thanks in advance.

If cleaning the PCB and switches solved the problem previously, there may be
something there that needs further investigation. Look vewy, vewy closely,
using a magnifying glass or other high-powered optics, at the CPB and the
area around the switches for anything that may look out of place. Like a
burned area such as may be caused by arcing. Have you used the DMM to check
a high voltage source just prior to it exhibiting the problem? How about
moisture or spilled liquid? Or component leads touching?
In this case, your eyes may be your best tool.

Cheers!!
--
Tweetldee
Tweetldee at att dot net (Just subsitute the appropriate characters in the
address)

Time is what keeps everything from happening all at once.

Multimeter won't zero, only on DC volts
 

On 02 Aug 2003 13:12:45 GMT, (WbSearch) wrote:

Have a Micronta M/N 22-191 multimeter that recently won't display zero only on
DC at the 2 volt selection or higher. The 200 mv scale is fine, as are all
scales of AC volts. The display shows between 0.100 - 0.500 volts, even when
the plus and minus leads are touched together. I have cleaned the PCB and
switches which helped for a short time. All diodes, resistors, batteries and
fuses check fine. All other functions work porperly as well. Any other help
is appreciated.
Also, does anyone know what the 2 POT's are for? The manual doesn't go into
that detail. Thanks in advance.

You may have checked this already but..............if it has a
rotary switch built into a circuit board then check to make sure
that no conductive smears have formed between the different
contacts of the switch.