26-10-2016, 03:45 PM
Re-read the VCM163 article I linked.
Almost all valve testers are essentially halfwave. Neither Analogue, ordinary DMM or even true RMS meters can give the same results as the built in meter calibration. That's why when I was replacing Valve tester meters:
1) Got a meter with same FSD current sensitivity. More important than terminal voltage or movement resistance, though it can help if close.
2) Scanned current scale.
3) Resized it to not just size, but arc of replacement meter, printed and fitted replacement scale
4) Did suitable calibration if possible.
You can usually calculate on external regular meter readings to find the actual readings if you know how the valve tester works and what your DMM or analogue test meter does.
Almost all valve testers are essentially halfwave. Neither Analogue, ordinary DMM or even true RMS meters can give the same results as the built in meter calibration. That's why when I was replacing Valve tester meters:
1) Got a meter with same FSD current sensitivity. More important than terminal voltage or movement resistance, though it can help if close.
2) Scanned current scale.
3) Resized it to not just size, but arc of replacement meter, printed and fitted replacement scale
4) Did suitable calibration if possible.
You can usually calculate on external regular meter readings to find the actual readings if you know how the valve tester works and what your DMM or analogue test meter does.
