If you look at the diagram for a full bridge rectifier it will be apparent why it tests open on the 'AC' side. There is no path for DC, it is like a bunch of valves that reverses the connection on each mains cycle.
I think the problem is that COM on a meter is not the same as battery ground, it is going to be floating at some midpoint reference. Maybe 3V for instance. Then the ADC can measure voltages above and below COM potential.
If what you did is to either short COM to battery ground, or to +9V, then it's very likely that the reference will have been damaged.
Unfortunately on many meters this reference does in fact come from the main ASIC.
I'll point people to this thread when they ask why anybody needs more than one multimeter.
I'll point people to this thread when they ask why anybody needs more than one multimeter.
Yep!
Sadly, this isn't the first post that I've read over the years of someone frying their meter trying to read the voltage of the internal battery.
It might be worth posting a warning about attempting to do this as a permanent sticky.
WoD
So we can consider the meter dead right? Replacing the FPGA from another meter would cost as much as a new one...ASIC, not FPGA. An FPGA is a very different type of device.
report back the voltages returned, as well as what is on the F177's LCD.
Here are the DSO captures for :LTC2435
As far as I know about SPI, SCK signal doesn't look good...(pin 13)
Before any of that though, can we recap on some earlier measurements? If the ADC is meant to be getting 3.3V and it's getting 5V that's not good. In the 8x series the ADC is supplied with +/- 2.5V, the REF and VIN are connected to GND. It would be useful to know which is correct for your case.
Before any of that though, can we recap on some earlier measurements? If the ADC is meant to be getting 3.3V and it's getting 5V that's not good. In the 8x series the ADC is supplied with +/- 2.5V, the REF and VIN are connected to GND. It would be useful to know which is correct for your case.
REF- is the only pin tied to GND.
VCC pin has 5V on it (datasheet says between -0.3V to 7V)
REF+ 2.5V
IN+ 2.5V
IN- 2.5V
All display related traces come exclusively from the microcontroller, most of them are on the top layer. So the ASIC has nothing to do with dispaly (I guess).
I've found a great offer for around 16$ shipped to my country (Romania, Europe) for the ADC and ASIC chips.
The question is, may it work with those things new? (I know meter will need recalibration).
But, I have a stupid question here, the ASIC comes already programmed, doesn't it? I know these things can do only one task... from Bitcoin mining ;D
Thank you for that intel. I'll order the ASIC and the ADC. Keep you guys posted with this.
Meanwhile is it a good idea to just desolder the current ASIC and power on the meter without it? See if the behavior changes in any way? :scared:
2. Is there a Fluke ASIC for switching the front-end ranges, like there is in the 8x series? Given your reported input impedance of 2-ish megohms, when it should be 11, I'd want to look more closely at this first.andyB2022: I would also look into what AVGresponding asked above, as Alonso tested you should have 11M input impedance but it is 2.5M on your unit.
UTE61E: AN8009:
OFF: 25.60M 36.4M
1V: 11.15M 10.982M
10V: 10.13M 10.085M
100V: 10.04M 9.995M
1000V: 10.03M 9.985M
I think the problem is that COM on a meter is not the same as battery ground, it is going to be floating at some midpoint reference.
Yeah, it's a bit out of my capability... An X-ray machine will do the job in seconds... Anyone here with something like that? Or maybe someone has a photo with the PCB already?
I bought the meter second hand (even tho was brand new) so no documents came with it. I've called an authorized repair center in my country and they told me that without some receipt / invoice when and where I bought it, they can't take a look at it.
I'll leave it in a drawer and check on it again when I'll have more time, for now I'm aiming towards an 87-V.
Since the OP doesn't live in the USA then the Brymen may make sense.
Since the OP doesn't live in the USA then the Brymen may make sense.
Are the Greenlee branded Brymens horribly overpriced or something? :-//
Are the Greenlee branded Brymens horribly overpriced or something? :-//
I've got an used 87 V which I enjoy better, maybe because of more features and more accuracy...
Still miss the robustness and slimmer feeling of the 17x series.
I do not see the 17x series as more robust than the 87x. The yellow cover of the 17x series tend to come off.They only come off if you get certain solvents/oils on the meter.