DVOM reads somewhat low

[m]

I acquired an old Micronta (Radio Shack) DVOM.

It generally reads about 8-10% low.
I have other DVOM's, 3 different brands all read the same, "good"
batteries act good in equipment, "low" batteries act low in equipment.
So I trust them, and this one is low.

I looked on the circuit board, no pots to adjust.

What is the usual/typical cause that results in a low reading?

MS

 

[Tim Kettring]

"ms" <msa@nospa.com> wrote in message news:40A5528A.B312181D@nospa.com...

I acquired an old Micronta (Radio Shack) DVOM.

It generally reads about 8-10% low.
I have other DVOM's, 3 different brands all read the same, "good"
batteries act good in equipment, "low" batteries act low in equipment.
So I trust them, and this one is low.

I looked on the circuit board, no pots to adjust.

What is the usual/typical cause that results in a low reading?

MS

Is it auto-ranging ? or do you have to manually select the range ? If it
manual range select , you probably have a resistor (s) half burnt in the
low range .

 

[Michael Black]

ms (msa@nospa.com) writes:

I acquired an old Micronta (Radio Shack) DVOM.

It generally reads about 8-10% low.
I have other DVOM's, 3 different brands all read the same, "good"
batteries act good in equipment, "low" batteries act low in equipment.
So I trust them, and this one is low.

I looked on the circuit board, no pots to adjust.

What is the usual/typical cause that results in a low reading?

MS

This is likely not a common cause, but I once had some problems (I can't
remember the exact details) that turned out to be a not-good fuse. It
wasn't outright bad, but it had indeed gone flakey or gained resistance.
I had the DVM apart, and cleaned the switch, and then caught on tht it
must be the fuse.

Michael

 

[m]

Tim Kettring wrote:

"ms" <msa@nospa.com> wrote in message news:40A5528A.B312181D@nospa.com...
I acquired an old Micronta (Radio Shack) DVOM.

It generally reads about 8-10% low.
I have other DVOM's, 3 different brands all read the same, "good"
batteries act good in equipment, "low" batteries act low in equipment.
So I trust them, and this one is low.

I looked on the circuit board, no pots to adjust.

What is the usual/typical cause that results in a low reading?

MS

Is it auto-ranging ? or do you have to manually select the range ? If it
manual range select , you probably have a resistor (s) half burnt in the
low range .

I'll look into that, a user could have measured on the wrong range and
damaged a resistor.

MS

 

[m]

Michael Black wrote:

ms (msa@nospa.com) writes:
I acquired an old Micronta (Radio Shack) DVOM.

It generally reads about 8-10% low.
I have other DVOM's, 3 different brands all read the same, "good"
batteries act good in equipment, "low" batteries act low in equipment.
So I trust them, and this one is low.

I looked on the circuit board, no pots to adjust.

What is the usual/typical cause that results in a low reading?

MS

This is likely not a common cause, but I once had some problems (I can't
remember the exact details) that turned out to be a not-good fuse. It
wasn't outright bad, but it had indeed gone flakey or gained resistance.
I had the DVM apart, and cleaned the switch, and then caught on tht it
must be the fuse.

Michael

That's a good clue- it happens the fuse was blown, someone wrapped it
in alum foil just to make a connection, so it has less resistance than
a good fuse.

MS