Does anyone know why my old micronta multimeter won't zero with the ohms adjustment? Then it gives me the wrong voltage reading for a small 9volt battery.

 

Note that a 9 V battery does not necessarily put out 9V. It can be as high as 9.5 V and anything lower than that.
What reading does it show for your 9V battery?

On ohms measurement, the meter is not particularly accurate. Try changing the battery inside the meter if it does not zero properly.

 

zeroing Ohms scale requires full scale swing which is maximum current used for resistance measurement. if that maximum cannot be reached, either battery need to be replaced or meter is damaged - indicator needle or swing mechanism are catching on something, or the circuit is damaged (worn out potentiometer, burned components).

to see if the meter mechanism is free to move, use it to measure known voltage. to be sure reading is correct compare with the reading by another meter. if the other meter is different (DMM) reading voltage of dead batteries will produce different results, because your unit has much lower internal resistance and old batteries have high internal resistance. to avoid such discrepancy, connect both meters to same voltage source at the same time.

 

Does anyone know why my old micronta multimeter won't zero with the ohms adjustment? Then it gives me the wrong voltage reading for a small 9volt battery.

What does "ohms adjustment" have to do with the voltage of a 9V battery?
You don't use the ohms setting to measure voltage.

 

To get a proper zero ohms reading on my old digital Micronta multimeter I need a few things.

1. Fresh batteries.
2. Quality probes.
3. Rotate the ends of the probes in their sockets to get a good clean connection.
4. Hold and press the leads together with a lot of pressure.

 

The volts function in an analog meter doesn’t require any batteries to operate.
The batteries are solely for the resistance function.
The exception to the rule above would be whether your meter was a FET VOM, but from your photo, it isn’t

 

yup, my guess was that he was using the meter to measure battery that was in it. that could explain everything...
but according to manual, this device uses single AA type battery.

to zero voltage scale, short the probes and turn little black knob and the lower edge of the display. battery is not needed.
to zero Ohms scale, short the probes (assuming inserted battery is ok) and use the red knob on the left, below display.

 

There is another possible explanation. My experience was with a similar meter given to me because "it had gone crazy" after the batteries had been replaced. Nothing worked right, not voltage, current, or resistance..
What I discovered was that when the previous batteries had failed, they discharged a conductive fluid mist that was a good conductor, and that had coated everything with a conductive film. My fix was a major washing off with denatured alcohol, brushed on and allowed to run off, several times. Then an air dry in the hot sun for a few hours.
With another meter that would not zero the ohms, it was corrosion on the battery connections. Again, a serious scrubbing with the alcohol and a brass wire brush removed the corrosion, and a small bit of electrical anti-corrosion grease solved that problem.

 

That meter is what, forty or fifty years old? It could be as simple as it's not working as well as it should because, like us and everything else, it's simply worn out. Maybe normal wear and tear, maybe something in it's long service that damaged it -- such as bent the needle a bit by getting connected to too large a signal at some point, which would account both for the inability to zero on the ohms and for too-low readings of everything else (you didn't say whether the voltage reading was too high or too low or how you even came to the conclusion that it was wrong).

But if that's not the case -- and the old Micronta meters, both analog and digital, were surprisingly well made, especially for the price -- then, as others have said, first put new batteries in it (for the ohms function) and be sure to compare the voltage reading with another, reliable measurement of the same voltage (keeping in mind that the other measurement is not going to be perfect, either). Do that and, if it's not resolved, come back and tell us what tests you did and what the results were and we can discuss it some more.

 

The first thing to check are the contacts for the battery connection. If ever a battery has leaked a bit, they can be corroded a bit and add some resistance, making a zero setting impossible. The second step would be to use some spray contact cleaner on the range switch. And then use a bit of the spray on the test probe jacks, because they can become a bit corroded.

 

The ohms adjust doesn't zero at that end of the meter, it zeros at the other end (FSD).
The zero end shown (to the left) is zero'd with the black screw head at the meter needle pivot point.

Given the smashed case in the picture, I should say I've fixed several meters failing to swing properly by cleaning metal crumbs from the gap between the armature and the magnets.

 

That meter is what, forty or fifty years old? It could be as simple as it's not working as well as it should because, like us and everything else, it's simply worn out. Maybe normal wear and tear, maybe something in it's long service that damaged it -- such as bent the needle a bit by getting connected to too large a signal at some point, which would account both for the inability to zero on the ohms and for too-low readings of everything else (you didn't say whether the voltage reading was too high or too low or how you even came to the conclusion that it was wrong).

But if that's not the case -- and the old Micronta meters, both analog and digital, were surprisingly well made, especially for the price -- then, as others have said, first put new batteries in it (for the ohms function) and be sure to compare the voltage reading with another, reliable measurement of the same voltage (keeping in mind that the other measurement is not going to be perfect, either). Do that and, if it's not resolved, come back and tell us what tests you did and what the results were and we can discuss it some more.

Multimeters really do not "wear out", except for possibly the range selector switch and the probe connection jacks. Certainly they can fall victim to abuse and incorrect use, and the carry handles do wear thru, but my Micronta multimeter purchased in 1969, still works very well. They are subject to mechanical injuries, but that is not the same.