AMPX1 Process Calibrator Multimeter - Page 1
Forum section: electronics / testgear

author: amspire
author_rank: Super Contributor
timestamp: October 10, 2019, 11:33:52 am
content: Here is some code to dump the USB output of the "INSANE A 0.02% Process Meter for $9? WTF" multimeter describes in Dave's #1248 blog.It is a modified version of the code from this site:https://sourceforge.net/projects/qm1571-multimeter/files/It gives a continuous output like this:+2.496 V DC, AUTO+2.496 V DC, AUTO+2.496 V DC, AUTO+2.496 V DC, AUTO+2.496 V DC, AUTOYou have to edit it for the correct COM port. This one is set to COM3, but check Device Manager for the correct port. For Linux, you will have to change it to something like '/dev/ttyUSB0'.It should work with Python 2 and 3, but I tested it on Python 3.7.Richard

author: amspire
author_rank: Super Contributor
timestamp: October 10, 2019, 12:08:59 pm
content: Found a couple of typo's. Here is an updated version.If the code from the multimeter is messed up, you get an output like this:-018.0 mV DC, AUTO-018.0 mV DC, AUTO? 17.2f.3d.40.55.67.7f.8f.9d.a0.b8.c0.c0.e8-018.0 mV DC, AUTO-018.0 mV DC, AUTOIn this case, there were two 0xC0's and the 0xD0 was missing.

author: amspire
author_rank: Super Contributor
timestamp: October 10, 2019, 01:18:27 pm
content: This program also works to capture the serial output of the AMPX1:http://www.postcogito.org/Kiko/UtSixtyEDecoder.html#FeaturesThis means that it should be possible to get Sigrok to work, but I haven't worked out how to use it yet. Sigrok-cli can see the Silabs CP2101 on the COM3 port, but when I run this:sigrok-cli -d uni-t-ut60e:conn=COM3 -C P1 --continuous -O analogit complains about no HID-PID. There should be a way to use the com port, but the documentation is very meagre.Any sigrok experts out there?

author: Smokey
author_rank: Super Contributor
timestamp: October 11, 2019, 08:54:43 am
content: Cool. Marked.

author: Electro Detective
author_rank: Super Contributor
timestamp: October 19, 2019, 10:49:37 pm
content: Quote from: amspire on October 10, 2019, 11:33:52 amFriendly FYI: the infamous'Metergate'blog post #1248 is at this url > eevblog.com/forum/blog/eevblog-1248-insane-a-0-02-process-meter-for-$9-wtf/

author: amspire
author_rank: Super Contributor
timestamp: October 20, 2019, 01:28:01 am
content: Quote from: Electro Detective on October 19, 2019, 10:49:37 pmThanks. I wanted a thread for the useful info on the meter. I actually managed to damage my first meter, so I have to do a bit of digging into the hardware now. Turns out the calibrate inputs have very little protection. Not sure what I did - I may have put 15V into the 10V input, or I may have had a negative polarity - the inputs are for positive polarity only. I think I have caused some semiconductor device to fuse shorted.Richard

author: Electro Detective
author_rank: Super Contributor
timestamp: October 20, 2019, 02:01:55 am
content: Ouch!post what you can here, am certain it will attract the usual suspects to help outand or suggest somenon sledge basedoptions and troubleshoots

author: maginnovision
author_rank: Super Contributor
timestamp: October 20, 2019, 02:26:07 am
content: Quote from: amspire on October 20, 2019, 01:28:01 amWhat sort of output are you getting now? I have one here counting up before resetting.

author: amspire
author_rank: Super Contributor
timestamp: October 20, 2019, 04:30:09 am
content: Something is completely shorted - even on Ohms I get 0 ohms. Obviously something different to your problem.Was the counting up only the calibration ranges?

author: maginnovision
author_rank: Super Contributor
timestamp: October 20, 2019, 04:50:58 am
content: Yes, my failure mode everything worked except calibrated output. Even then if it's set to <2V it outputs 0. After 2V it goes 0-10V pretty quick. One of the opamps is very hot and both of its outputs also count up(and down) so 0-5V and 0-(-5)V. I haven't had a chance to look at it with a scope though, and it's not an easy board to follow with vias everywhere and sort of a messy layout.

author: amspire
author_rank: Super Contributor
timestamp: October 20, 2019, 04:57:18 am
content: I think it will be very valuable to work out the calibration circuit since it can be damaged far more easily then a conventional multimeter.In your case, a hot opamp sounds like a problem that could be solved easily with the help of a circuit.

author: maginnovision
author_rank: Super Contributor
timestamp: October 20, 2019, 05:13:20 am
content: I just scoped the output and it's odd. Maybe a failed dac?

author: BradC
author_rank: Super Contributor
timestamp: October 20, 2019, 05:14:29 am
content: It'd be interesting to pop a PIC ICSP on and see if they enabled code protection.

author: thm_w
author_rank: Super Contributor
timestamp: October 21, 2019, 11:00:06 pm
content: Quote from: BradC on October 20, 2019, 05:14:29 amJ1 pinout:1: Vpp/mclr2: 3.3V3: ground4: ICSPDAT (RB7/pin 37)5: ICSPCLK (RB6/pin 42)It says it reads out the file OK, verifies OK, but the hex file is all 00's so I assume its protected.Normally you'd see a read error no? I'm using mplab IPE v3.edit: PIC16F1947