RS-232 output - I can't see the IC TXD pin bonded.
1. Change Amps to mA - I know you've stated that it can be done by changing shunt resistors but can the EEPROM also be hacked to give the correct display? I don't want to measure Amps, just mA and uA.
Any other low-hanging fruit?
1. Change Amps to mA - I know you've stated that it can be done by changing shunt resistors but can the EEPROM also be hacked to give the correct display? I don't want to measure Amps, just mA and uA.
Quote1. Change Amps to mA - I know you've stated that it can be done by changing shunt resistors but can the EEPROM also be hacked to give the correct display? I don't want to measure Amps, just mA and uA.
I changed the 0.01 ohm shunt resistor for the AmA jack to 0.095 ohms and now with the leads in the COM and AmA jacks, but the AN8008 rotary switch in the uA position, I measure mA current up to 99.99 mA with 0.01 mA resolution and 0.1 mA resolution up to 999.9 mA with the decimal in the correct location. 999.9 mA is the maximum current which can be read now. The mA readings are now typically 0.35% high. I haven't tried to change the meter's software yet. Others might need a slightly different value shunt resistor.
Thanks, what size is that 0.095 Ohm resistor?
RS-232 output - I can't see the IC TXD pin bonded.How did you check this?
For one AN8002 unit I removed die potting epoxy to reveal pin 20 pcb pad. I added a pull-up resistor and measured the signal. Nothing was visible. I sacrificed this unit and removed the potting epoxy to reveal the bonding wires and the die. The pin was unbonded.
RS-232 output - I can't see the IC TXD pin bonded.How did you check this?
For one AN8002 unit I removed die potting epoxy to reveal pin 20 pcb pad. I added a pull-up resistor and measured the signal. Nothing was visible. I sacrificed this unit and removed the potting epoxy to reveal the bonding wires and the die. The pin was unbonded.
For lowest cost, I assumed unused pins would not be bonded out. TXD would be very useful for testing.
Here is the region on the PCB I guessed TXD would be brought out. I do not see any traces there, however I do not have the exact die pinout. I'm not using the QFP pinout.
What are you using for a solvent on the encapsulant? TXD may very well be accessible.
Missing are the 9.999mA and 99.99mA ranges.
Right now, it has 10mR and 100R shunts only.
There is a IC (QFP) footprint under the encapsulant. The die is bonded to the inner end of the pads. So you can carefully remove the encapsulant to reveal the outer end of the pads without harming the bonding wires. I just used hot air to soften the encapsulant and removed it carefully with a surgical knife. The TX pad is the fourth from the top on the left side in your image. Check the DTM0660 datasheet pinout.
There is a IC (QFP) footprint under the encapsulant. The die is bonded to the inner end of the pads. So you can carefully remove the encapsulant to reveal the outer end of the pads without harming the bonding wires. I just used hot air to soften the encapsulant and removed it carefully with a surgical knife. The TX pad is the fourth from the top on the left side in your image. Check the DTM0660 datasheet pinout.
Ok sounds good, maybe post a pic I have no idea what it looks like under the blob.
Part two to getting serial data output is hitting the RS-232 button. Oh wait we don't have one
The button matrix is 2x3 mux and "REL/RS-232" button should be PT1.0 pin 42 to EEPROM SDA, both traces are available.
The AN8008 has oddball button assignments in firmware.
The DTM0660 datasheet gives two schematics for a 3V multimeter; 13.1 QFP and 13.2 with die pinout. The pin numbers are much different, some pins are joined 2-1, at the corners or power pins.
MY meter now reads XXX.X and XX.XX mA readings with less than 0.1% accuracy.
Due to the 1% resistors involved, other meters might require that a 2.2 or 2.0 ohm resistor be used in place of the mentioned 2.1 ohm resistor to achieve similar accuracy on your meter. The approximately 5% change in resistor value will only change the parallel resistance by about 0.23%. So, an even greater change in the value of the 2.1 ohm resistor might be needed.
Less than 1% accuracy? You mean more than 1% error?
And, yes I mean better than 0.1% accuracy using a hand selected 1% resistor to provide the best accuracy. I don't think that this model meter warrants any effort for better accuracy than that.
uV resolution has unneeded gap around zero (shows only 0 or -5uV or +5uV - nothing between), toy like.