A
[email protected]
- Jan 1, 1970
- 0
How do DMMs measure resistance? I was testing some relay coils that
are specced at 50 ohms resistance, but they read 0.5ohms on both
"Brand X" DMMs we have at work. If the DMM was in manual ranging in K
mode, it would have read 0.05. The coils don't have built-in snubbers.
Naturally I will confiscate these meters Monday morning, but I want to
know what's going on here.
At home, on a 10$ Mastercraft made in China analog meter, they read 50
ohms. On a Tektronix 249 DMM, they read 50 ohms.
The last time I put a scope across a DMM while it was measuring
resistance I saw narrow pulses. This must cause the coil to react and
cause false readings on naive DMMs?
are specced at 50 ohms resistance, but they read 0.5ohms on both
"Brand X" DMMs we have at work. If the DMM was in manual ranging in K
mode, it would have read 0.05. The coils don't have built-in snubbers.
Naturally I will confiscate these meters Monday morning, but I want to
know what's going on here.
At home, on a 10$ Mastercraft made in China analog meter, they read 50
ohms. On a Tektronix 249 DMM, they read 50 ohms.
The last time I put a scope across a DMM while it was measuring
resistance I saw narrow pulses. This must cause the coil to react and
cause false readings on naive DMMs?