I did a video on the TM3B as well, even having the rear cover off effects the readings. I mounted a PP3 battery holder on the outside of the rear panel so it makes it easy to pop a new battery on as needed.
This is a nice idea and got me thinking. Actually, rather than adding a RMS converter, I just connected a normal TRMS-capable multimeter to the output terminals of the TM3x. This works great. The problem with TRMS chips is that they need relative high signal levels which limits low you can measure. Even very expensive meters do not go below 5mV or so. Yes you can see lower voltages but if you check the specs, any claim on accuracy is gone. Using the TM3x amplifier solves this problem and you can measure TRMS with a normal (TRMS) digital multimeter down into the microvolt level ! I think I may even do another video on this because its so neat. The only caveat is that the analog output is always scaled to 0..150mV AC so when you use any TM3x range that goes 0..500 you need to do some math to convert the digital readout.
@@TheHWcave I also have BM869s, absolutely hate the fact that it can't read Freq and RMS at millivolts. So I diy'd a 20/40 dB preamp in an Altoids cinnamon mint tin with 9v battery (TM3B is a little more extravagant) ...and another PET PIEVE, why don't digital scope manufacturers put DAC for the vertical output on the back like the old dinosaur analog CRT beasts? It would be nice to have the vertical amplifier after the range switching direct out?
I did a video on the TM3B as well, even having the rear cover off effects the readings. I mounted a PP3 battery holder on the outside of the rear panel so it makes it easy to pop a new battery on as needed.
That is an excellent idea. I will do that as well.
Nice find! Plenty of room to add an RMS convertor, DIY or off the shelf chip.
This is a nice idea and got me thinking. Actually, rather than adding a RMS converter, I just connected a normal TRMS-capable multimeter to the output terminals of the TM3x. This works great. The problem with TRMS chips is that they need relative high signal levels which limits low you can measure. Even very expensive meters do not go below 5mV or so. Yes you can see lower voltages but if you check the specs, any claim on accuracy is gone. Using the TM3x amplifier solves this problem and you can measure TRMS with a normal (TRMS) digital multimeter down into the microvolt level ! I think I may even do another video on this because its so neat. The only caveat is that the analog output is always scaled to 0..150mV AC so when you use any TM3x range that goes 0..500 you need to do some math to convert the digital readout.
@@TheHWcave I also have BM869s, absolutely hate the fact that it can't read Freq and RMS at millivolts. So I diy'd a 20/40 dB preamp in an Altoids cinnamon mint tin with 9v battery (TM3B is a little more extravagant)
...and another PET PIEVE, why don't digital scope manufacturers put DAC for the vertical output on the back like the old dinosaur analog CRT beasts? It would be nice to have the vertical amplifier after the range switching direct out?