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| Amazon Commercial 90DM600 multimeter hacks |
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| sequoia:
Amazon Commercial 90DM600 DMM appears to be a rebadged CEM DT-9560/9561 meter. This is a rugged (IP67 certified) 6,000 count meter that has Intertek/ETL safety certification and currently sells for about $30 (US): https://www.amazon.com/AmazonCommercial-Count-Compact-Digital-Multimeter/dp/B07W3BXNMP/ Chipset is DM1106EN (found on many meters from UNI-T, Victor, etc...) that stores its configuration/calibration data in a 24LC02B (2Kbit) I2C EEPROM. Searching information about this chipset brought up multiple threads here on this forum about hacking UNI-T, etc. meters based on this same chipset. So it would appear it is possible customize settings on this meter and possibly enable 10,000 count mode (as chipset appears to support it). I was able to dump the EEPROM using a CH341A programmer using a SOIC8 test clip and temporarily holding CPU in reset mode by grounding R25 (end that connects to IC1 pin 55) to the PIN 1 on the Program header. Meter needs to be powered on (I used the V~ setting). No soldering needed if you have steady hands :) EDIT: To be extra careful, I may be best to use "pull down" resistor (1k to 10k range) to hold CPU in reset. NOTE! Most (if not all?) CH341A programmers have flaw that Vcc is 3.3V but the signals are 5V, so using a unit that is not fixed, might damage your DMM... (This post shows one possible fix: https://www.eevblog.com/forum/repair/ch341a-serial-memory-programmer-power-supply-fix/msg1347050/#msg1347050) Backup of factory settings of the meter: --- Code: ---0000000 ff ff ff ff ff ff ff ff ff 52 00 0e 01 e8 d4 03 0000010 10 27 38 18 4e 02 66 66 3d 3d ff 3b 0a ff 40 ff 0000020 bb 99 1b 81 fa 00 32 00 00 80 2d 8d ad 8d 95 f7 0000030 4e 02 09 04 12 09 6b f8 0a d0 1b 0a 1a 01 0a 00 0000040 00 01 00 01 00 07 98 00 64 00 64 00 64 00 c0 00 0000050 00 80 00 80 00 80 00 80 00 80 00 80 00 80 00 80 0000060 c4 7f bd 84 01 00 0c 2b 00 00 00 00 00 00 00 00 0000070 28 80 00 80 a4 83 e8 7d 0a 27 00 00 00 00 00 00 0000080 00 00 00 00 00 00 11 0f 00 13 0d 12 02 07 04 03 0000090 00 00 00 00 00 00 10 0e 00 15 0c 00 01 0a 00 00 00000a0 00 00 00 00 00 00 00 00 00 00 00 00 00 09 00 00 00000b0 00 00 00 00 00 00 00 00 00 00 00 00 00 0b 00 00 00000c0 0d 00 02 20 0d 00 03 20 20 00 03 20 20 00 03 10 00000d0 41 00 03 08 41 00 03 05 41 00 03 05 0d 00 02 20 00000e0 e2 f1 0b 80 00 80 db 7f cc 7f a6 7f 9d 7f 00 80 00000f0 00 80 00 80 00 80 00 80 5a c6 ec 0f 05 00 00 00 --- End code --- Comparing this to examples found in thread https://www.eevblog.com/forum/testgear/a-look-at-the-uni-t-ut210e/ seems to point that it should be possible to "hack" this meter by by reprogramming the EEPROM. Lot of information about modifying EEPROM for DM1106EN/DTM0660L chipsets can be found at: https://github.com/bdlow/UT210E It would seem like it may be possible to modify this meter to 10,000 one and possibly even enable the temperature measurements mode (to make this functionally same as the more expensive 90DM610 model...) |
| Muttley Snickers:
--- Quote from: sequoia on May 01, 2020, 04:16:36 am ---So it would appear it is possible customize settings on this meter and possibly enable 10,000 count mode (as chipset appears to support it). --- End quote --- Nice work but what about the LCD ? :-DMM ??? The LCD layout in the image above appears to be for a 6000 count or less meter as the DC icon is in a position where it would conflict with any additional digits. I suspect their higher count models probably have a completely different layout in the display when compared to the lower count models. |
| sequoia:
--- Quote from: Muttley Snickers on May 01, 2020, 06:41:29 am ---Nice work but what about the LCD ? :-DMM ??? The LCD layout in the image above appears to be for a 6000 count or less meter as the DC icon is in a position where it would conflict with any additional digits. I suspect their higher count models probably have a completely different layout in the display when compared to the lower count models. --- End quote --- LCD is 4 digits only, so cant get 10,000 count but should be able to get to "9,999 count"... Looking the factory EEPROM settings it would seem full range value is set from factory to 10,000 counts (0x2710). And and upper limit (for automatic range switch) is set to 6,200 (0x1838), so presumably changing that to 9,999 (0x270f) might work? |
| sequoia:
Success! I was able to enable temperature measurement by adding those modes to the "Hz %" selector setting (now pressing mode button toggles between "Hz", "C", "F" modes). I also changed successfully uA, mA, A, and mV ranges to default "DC" mode instead of factory default "AC"... To update meter save copy of the original settings and then edit following locations: |
| sequoia:
I guess this could be called "9999 Counts" ? I changed factory limits for the autoranginng: upper limit changed from 6200 to 9999, and lower limit changed from 590 to 990: |
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