Hello,
I have an Voltcraft VC-523.
This clamp-multimeter is based on an DTM0660L too.
I tried to read out and change the EEPROM data to switch on data output via EUART TX and switch off auto power down.
While the last is working the data output does not.
I connected an 1k resistor as pullup and hooked up the scope.
Switching on the clamp meter and then pressing and holding the REL key until it beeps - but still no data output.
Hm. When I understand the datasheet for HY12P family correctly, the TX pin must be activated as such inside the ROM (not EEPROM).
If so, there will be no chance to get a data output.
Can anyone confirm this?
BTW: Two pictures of the PCB and the two EEPROM dumps (original and modified).
The op amp for the current clamp is an OP07 (instead of the chopper type op inside the UT210E).