Hacking DTM0660L based Multimeters

[AlphZeta]

I picked up an ennoLogic eM860T multimeter a while ago, and as it turned out this meter is also based on the single chip design based on DTM0660L (quite a few meters I know of use this chip, such as UNI-T 139C, Velleman 4100, Tekpower TP40...) Because the calibration and configuration data is stored in an external EEPROM, it is actually quite easy to hack this thing (e.g. enable RS232/UART, change range switching point, backlight duration, auto timeoff duration, etc.).

I did a write up on this (http://www.kerrywong.com/2016/03/19/hacking-dtm0660l-based-multimeters/) and also did a quick video:



The datasheet can be found following the link on (https://sigrok.org/wiki/Multimeter_ICs). Note that the datasheet is available in Chinese only. But if you are interested in it I can translate it and post on my website. Sigrok supports this chip already so if you enable the RS232, you can log data with it.

[AlphZeta]

For those who are interested in the datasheet, I just translated it into English and the PDF version can be found here: http://www.kerrywong.com/2016/04/03/dtm0660-datasheet-translated/

[PedroDaGr8]

That is really cool! Great job, nice of the meter maker to make things really easy for you (with the resistor already soldered) and the easy pinouts available.

[AlphZeta]

That is really cool! Great job, nice of the meter maker to make things really easy for you (with the resistor already soldered) and the easy pinouts available.

Thanks @PedroDaGr8! Yeah, I was wondering if ennoLogic had a RS232 enabled version of the meter. But they didn't, the eM860T is the only meter they offer. It probably is just a re-badged meter anyway as there are many meters out there sharing almost identical designs.

[vinibali]

Hello there!
I have a Zeast282 multimeter which uses a HY12P65. That might be the original OEM processor for this DTM0660L.
I was able to change the backlight and power off registers with the tutorial, but I was not able to switch on the UART.
Long pressing the REL just activated the REL function immediately and doesn't let it to switch on the UART.
Do you have maybe any ideas, how could I get this work?
Thanks

The other thread for Zeast282 is here:
https://www.eevblog.com/forum/microcontrollers/multimeter-eeprom-modding-zeast282-rxtx-enabling/

[shianne]

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).

[Texmisure]

Which chip is used by Uni-t Ut139b? Thank you.

Tom