Re: [Amateur-repairs] Calibrating test equipment?

Hi Mike

It is quite obvious  for Analog meters, but the same has happened to ones that read in base 10 digits; one range  goes  bad. Perhaps those use manual ranging. I'm not even a micro expert. I don't know how any of the auto-Ranging  schemes actually work, so have no idea of how such a "failure" mode can happen, but is has happened and the nearly 50% error was …eventually… diagnosed and reported on another Forum.. The failure is in the meter..Not the radio!

End …don

From: Amateur-repairs@groups.io [mailto:Amateur-repairs@groups.io] On Behalf Of Mike Dinolfo via groups.io
Sent: Saturday, July 26, 2025 10:18 PM
To: Amateur-repairs@groups.io
Subject: Re: [Amateur-repairs] Calibrating test equipment?

 

Don Root:

 

Excellent point.  And analog multimeters, in particular, typically switch between different circuits, with different resistances, for different measurements.  The measurements might be quite accurate on some particular range(s) or measurement(s), but wildly inaccurate on others.

 

I have probably a half dozen analog multimeters that I've acquired over the years.  Most of them (on voltage measurements, at least) tend to agree closely with each other.  But there are exceptions.  I have a Simpson 260 series 2 (1960's vintage) which is great- consistent measurements, and acceptable accuracy IMO.  And a Simpson 240 (vintage 1960's I _think_) which I believe was mis-wired, possibly at the factory, and even after correcting the mis-wiring is only accurate to +/- 25% on some ranges.  I keep it as an interesting item, but don't use it for measurements.  If you don't have a laboratory-accuracy-traceable instrument, all you can do is compare one in-hand instrument's readings to that of another, and go with it.

 

Analog multimeters (as one example) might be quite accurate and consistent on certain ranges but unacceptably inaccurate on other(s).

 

"An individual with one watch knows the time.  An individual with two watches is never sure."

 

Mike N4MWP

 

On 7/26/25 19:08, don Root via groups.io wrote:

Hi David , that verifies one range on DC .. good.. but what about all the others. We have seen where people trust the meter so much than they don't believe that it is ONE input range that is "out" by a factor of 2  maybe;  not exactly a "calibration" problem, but…

---don---

 

From: Amateur-repairs@groups.io [mailto:Amateur-repairs@groups.io] On Behalf Of David VK2CZ via groups.io
Sent: Saturday, July 26, 2025 6:12 PM
To: Amateur-repairs@groups.io
Subject: Re: [Amateur-repairs] Calibrating test equipment?

 

Hi Tom,

Fully agree that petrology calibration costs are prohibitive for the average punter.  I use what's called a 'transfer' method to validate voltage measurements. 

 

This involves something as simple as say a lithium button battery, where you physically take that battery to a place that has say a 7.5 digit multimeter, log the reading, then compare it to your own multimeter.. 

 

David Burger VK2CZ 

--
73  don va3drl