EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: itsthatidotagain on August 03, 2016, 11:00:26 pm
-
I picked up a Victor VC921 True RMS pocket multimeter to add to my growing pile of ultra cheap (and mildly hazardous) multimeters used mainly for low voltage microcontroller hacking, and naturally the first thing I did was take it apart.
(https://lh3.googleusercontent.com/CP4CaE8mvsQgV0PW9RxWPHOXmkJGQh4X6-UYxtIEN9RUDTYtRYsZVwxfoATSUbJLLjgxLqoMfcuxNngfQq39xQo9m55CCnFcYIyUtu13mCCGrvJXPKG1xtIW-afXsivsH4koE2zJlfvqu9SQ1CKgmqsZGZxR_WFGJ87cxtibi-joo0hyPcSAzgaKDxKWJ39-lrzj9_mqUwOP414M8Phqin8Z_pykwquXTIW1qXq2D-YjJzFmPb77bBJeH_SFvLEpmYD1E_AZnKsBoIfc7dUvcDoKTQcDLZqlsTRKp3dTUcJu4jsI7Xv1o7krymHc4HbPQvp9UCqDkWOOCSBCNawHeee2_DuFhZQhNGoR-MgHfCaSgmSt06RxlqBvCMDSwrSQAG_XpzNy6PTx6ncHF_E1wQWRVXvpdRF0n4ROYDd2O2ucBnVEwrt6b9WQWaEWWvaWEQPz0_3zRYrNB2-Q_PsegNONL4ZgjCFsg7-Sfu3oceKMDooJ4VnCdDQ6BOo09MqapW_ZnHEgVAePCYXng_875JUVMdUm3cbQWuluE8OjvEZJpot8i52rAe-mJb4zOCPvmu4phNJpvmfDSQcRsEdqGMpw1-mzyxQ=w480-h639-no)
It seems there are at least two variants of this meter, the one I have is the 4000 count "true RMS" variant.
It turns out this meter is based on the DTM0660 chipset, which means it is possible to hack in a serial port (using an optoisolator IRLED and a 100 Ohm resistor), so that mod was promptly done. NOTE: You will need to update the contents of the 24c02 eerom to switch this on.
More details here. (http://www.kerrywong.com/2016/03/19/hacking-dtm0660l-based-multimeters/comment-page-1/#comment-876829)
For additional fun, I also modified it to 8000 counts.
It should also be fairy simple to add a Select and Hold button, and perhaps even Temperature modes.
A full set of teardown pictures are available here... (https://photos.google.com/u/0/share/AF1QipPykJgrz2vMySXTkFdst6YsfoTs0Mzs1vmWZXa-XQ5EGBxVeRmFiqj-jO2c44IFcA?key=T01ITXVCa015U0x5WV9UZUV6dUdiSGdXUTBENF93)
(https://lh3.googleusercontent.com/2o3F98yZ3p9yGBR4rAwLM8e_VGOMKZ5LW-km_2I7iHLdabDmVdSQxbLpYfJUNPhQ6AOmQ5bbPvblgNeOKQdtr5jghzRV5_seqUMjjTK-mtAep18TJl2W2I2s_Odvjg_YUCqnNDwuORveQaKruRMRVKf7f1I-TRZ4-1sso3SGYyq5RAzGey8NDS5hv5leNeLxM2W1enURWK1xWCpuUkHJbjyEVUmNMbaJZuAr2_Dp3rtwJqFomOnO6zVEQc2_xc560iC47D6RIopyX6l3vNAFiNmHYxQUDvDF1kReo_Tw6dYiufLI0ZPosl7Tc_Raq2hhD831bu784Lo_jZtB1t6sFNhSmpvA_tDV2chWUQ5Q8fnDW9hOhAwFLkjBA0TNyYhTrilfRXoOYR-2XiOCzW2SmvkOz0pWNaGTNVKAg2maLh9mk66C-7MmbwknL8dCxHkfKoZTXnyzOAMzcUJd_pUAnipZTXcSkaAQPwnIVhXm7DR7ArQkTEPI25VujPNw6qshiddE_nSNZCl4qhYUzs2puYJYsUhbP7gvWtVi7IQNoKcZ8IKKyd-ltkxyhAr90ko2ZNKRXp0yAkXSqfNBYgjAzBTZluAXNW8=w618-h639-no)
I also added the DTM0660 protocol to QtDMM (a Qt based DMM readout and logger).
Code on Github here.... https://github.com/pingumacpenguin/QtDMM-DTM0660-Version (https://github.com/pingumacpenguin/QtDMM-DTM0660-Version)
(https://lh3.googleusercontent.com/W65bDyfgaUl1pokRrqAhvMveFaACmSuEG7O0h6HT8y9wqFNLDXO0A-yTZ7eN-160ASnTEzAy3tjMy73TvPVYy0pMsbjUVN7wmw4D7c2b061Fm0Beq9cRmV3JqJCdZi3f7X1BtPAaBgOM4m_iew5EkaNi0gOXcHbOykN2auKJ09BoU4b0xFZWJp7rHID6xsVCd7TguY0_rxPOGxZ4rNjq5nwGZkH1rF5mghK76NfA3NGYHGfWj0pJLJ-3dLwzgRzl4MtOWKgAPjpVvSHl8u4Id5NOFBWAdwZbAeAqp9IzaqPIUloXTb5pj4s7ey9U4nm8F9tBhOx_AOixU5deEXq6OE0uXsKZjfIEfowcH7UPhYVdlnAA01OBBtCtuVq1f1ELlEC7ZWRNDZyL7R8nx62qYHvKEZEeTS7m5pEsNxH11k0tW3-aI7K_TZ1iBg5mmtis876pwY1soyt490m8Cfei_FlnJKjDuS8QaT3GyvoRR18kZFDv3WC6aHf5E6AnDa3vD9dqDjeleDXIJCA5HqJdrx5b1vFSvYe1pUe8FF1Mw5P0E4nGFiKdea-yiqHYUMw8UlrMsbYP4YWq2lKf62A8TZxy_wbVvEQ=w614-h342-no)
Enjoy. :-+
-
Some reading from Russia:
While versed with his instrument, a lot of looking for information, came across the instrument baby Victor VC921 several times. Think again failed to include in its frequency device, then buy something else with a frequency counter. VC921 has multiple versions, I was looking for just such where they were and Hold the Select button under the battery cover. ... I bought and upgraded.
ALL WORK MODES!
Scroll down and use google translate
http://kazus.ru/forums/showthread.php?t=112135&page=68 (http://kazus.ru/forums/showthread.php?t=112135&page=68)
more
http://kazus.ru/forums/showthread.php?t=112135&page=69 (http://kazus.ru/forums/showthread.php?t=112135&page=69)
-
Some reading from Russia:
While versed with his instrument, a lot of looking for information, came across the instrument baby Victor VC921 several times. Think again failed to include in its frequency device, then buy something else with a frequency counter. VC921 has multiple versions, I was looking for just such where they were and Hold the Select button under the battery cover. ... I bought and upgraded.
ALL WORK MODES!
Scroll down and use google translate
http://kazus.ru/forums/showthread.php?t=112135&page=68 (http://kazus.ru/forums/showthread.php?t=112135&page=68)
more
http://kazus.ru/forums/showthread.php?t=112135&page=69 (http://kazus.ru/forums/showthread.php?t=112135&page=69)
Thanks for that, I had already read it, but it makes interesting reading for those following on. If you look carefully at http://kazus.ru/forums/showthread.php?t=112135&page=69 (http://kazus.ru/forums/showthread.php?t=112135&page=69) the image of the DTM0660 based variant includes my knees. :-DD alvadep has "borrowed" the image from my Google Album here => https://photos.google.com/share/AF1QipPykJgrz2vMySXTkFdst6YsfoTs0Mzs1vmWZXa-XQ5EGBxVeRmFiqj-jO2c44IFcA?key=T01ITXVCa015U0x5WV9UZUV6dUdiSGdXUTBENF93 (https://photos.google.com/share/AF1QipPykJgrz2vMySXTkFdst6YsfoTs0Mzs1vmWZXa-XQ5EGBxVeRmFiqj-jO2c44IFcA?key=T01ITXVCa015U0x5WV9UZUV6dUdiSGdXUTBENF93)
The rest of those pictures might also help anyone trying to replicate the hack.
This might also be of interest. http://stm32duino.com/viewtopic.php?f=45&t=1296 (http://stm32duino.com/viewtopic.php?f=45&t=1296)
-
Ready for surgery.
As far as I can understand:
Anode of LED to pin 8 on 24c02 and cathode of LED to pin 20 on DTM0660? Series resistor to the most convenient pin.
Make sure I have +3,3V on pin 8 / 24c02 from programmer as a power supply while programming.
Anything else to consider?
-
Do they also sell a version with all options provided by the chipset enabled by default?
How much does that one cost extra?
Or is that one not sold under Victor but under another brand?
-
I think I am in need of a helping hand...
I have got this programmer and clip as sugested in the UT210E tread.
http://www.ebay.com/itm/252228485325 (http://www.ebay.com/itm/252228485325)
http://www.ebay.com/itm/252135254293 (http://www.ebay.com/itm/252135254293)
I use the parallel driver and program version 1.13 from here
https://tosiek.pl/ch341-eeprom-and-spi-flash-programmer/ (https://tosiek.pl/ch341-eeprom-and-spi-flash-programmer/)
because virustotal.com indicates no extra payload in the *.zip for 1.13.
I have seen this on youtube
https://www.youtube.com/watch?v=L0ChYNwunUE (https://www.youtube.com/watch?v=L0ChYNwunUE)
and I am aware of the correct orientation of the clip and the program says the programmer is connected so I assume the driver is OK.
I have +3,3V on pin 8 / 24c02 and the same on pin 56 / HY12P6x.
When I try to read the 24c02 I get only 00 00 00...
If I try to read without connecting the clip I get only FF FF FF..., so something is alive.
I can choose between different manufacurers in the program, and I have selected 3V chips, all 24c02 of course. Same result for all.
What have I got wrong? :-//
I have zero experience with seraial EEPROMS. The VC921 apperas to be OK after the reading so I guess I have not damaged anything.
-
I have a lot to learn...
I read about another CH341 programmer, and it seems like they are not meant for in-circuit programming on the fly. A suggestion was to stop the targets x-tal oscillator. I paralleled the x-tal with a 1k resitor, and now I have read the chip. Next will be to figure out how to program it.
-
Conclusion:
The cheap CH341 prorammer can read and write to the 24c02 if we clamp down the x-tal oscillator. No other modifications needed.
I used a 1k resistor because I dislike to short pins on an IC without being sure its OK.
At the moment I have a flashing led and a nice pulse-train on my scope when the RS-232 function is activated. ;D
I need to tweak the optical receiver as I use other parts than suggested.
-
Some tweaking got me a working optical receiver.
Our Russian friends suggested a software from PeakTech.
They are obviously nice people, so they offer the software free of charge to everyone. ;D
http://www.peaktech.de/productdetail/kategorie/software/produkt/dmm-tool-basic.1034.html (http://www.peaktech.de/productdetail/kategorie/software/produkt/dmm-tool-basic.1034.html)
I used the large complete ISO version, but I think the smaller EXE will do as well. There are no need for drivers to be installed, except the one for the serial to USB coverter. Be aware that the files are compressed with Win rar. A free evaluation copy will do. http://www.rarlab.com/download.htm (http://www.rarlab.com/download.htm)
When installed, select PeakTech 3415 as device in the connection tab, and off we go.
I noticed that the transmitting LED in VC921 is still lit when the instrument is automatically powered off. No problem with manual power off.
Next will be to try bluetooth serial communication.
Proof of function.
-
I have played more with this little cutie.
"macboy" gave inspiration to try the mV-ranges.
https://www.eevblog.com/forum/testgear/canadian-tire-mastercraft-dmm-new-and-old-revision-teardown/msg927276/#msg927276 (https://www.eevblog.com/forum/testgear/canadian-tire-mastercraft-dmm-new-and-old-revision-teardown/msg927276/#msg927276)
They are available here too, and seems quite useful. They must be programmed to either the ohm, capacitor, diode or continuity position of the rotary switch. I don't use continuity, so it became DCmV. Continuity became a second function under ohm, so it is available. If you don't want to add the "select" button and have no need for one or more of the original four switch positions, you just program for instance DCmV as first on continuity as I did.
It's a lot of info floating around on the internet about the DTM0660, and I have tried to compile the most useful for VC921 into the modified HEX-dump attached.
As of today I have RS232, 8000 count scale length, temperature in °C and °F, warning level of 110V AC/DC and overload for 120V AC/DC (I don't trust VC921 for 230V) NCV, and toggle between AC and DC when in ACV or DCV.
I have found that the TX-LED for RS232 becomes lit when the instrument enters auto power down, so I have disabled APO. I have also found that the warning and overload does not function as expected if programmed to a value below 100V. In my instrument with 8000 counts, the warning did not work at all, and it entered overload at 80V regardless of what I programmed. From 100V upwards it seems to be OK. In the Chinese datasheet for DTM0660 they suggest a 500 ohm resistor in series with the TX-LED. I have not encountered any problems using that, and the benefit is less current consumption.
I am awaiting some small micro push-button switches from China so I can get the "select" on front of the instrument. While waiting I made an X-ray like image with a 5mm raster to help finding some free space for the switch. I attach it here.
-
Hi,friends! :)
On a photo buttons which I used are visible. I changed a firmware to 10000 counting, flight normal. On a photo comparing with HP-890CN when sampling about the ION of AD584-10Volt(Agilent=9.98857) and also from independent reference supply source of Uout =8.9027.
On measurement of capacity - upper limit 99.99milliF. The lower limit at VC921 managed with the help of constants to be held on to 50 pF. Self-correcting of zero on capacity in a firmware at it is driven into minus if to draw out up, then nonlinearity of measurements appears.
On measurement of frequency in the "Hz" mode - I decided to check an upper limit. Apparently on a photo, takes also 100 MHz, but in case of Vpp>10V from the generator without loading.
-
Hi indman, I try to follow the Russian forum but some details are lost in translation.
I can see that some of you use a separate button for Hz/Duty. What is the reason for that? Do you get access to more functions than by using a combined Hz/Duty and REL button?
-
Hi, tronde! Yes, I added 3 buttons on the front panel of a multimeter. I will explain functions of each button. "Hold/Backlight" - can add illumination of the display and holding of indications. "SELECT" - if to retain this button clicked in case of switching on of a multimeter, then the APO mode won't work, also this button has awakening function if the device entered a doze mode. "Hz/Duty" - this button allows to include measurement of frequency in the mode V ~.
I think that clear I explained everything, excuse for my English! :)
-
"Hz/Duty" - this button allows to include measurement of frequency in the mode V ~.
OK, so when you use a separate Hz/Duty button you get the option of frequency in ACV. What have you changed in the EEPROM to achieve this?
I have seen some images published in a zip-file by AST78512 (18.07.2016, 14:47 ) http://kazus.ru/forums/showthread.php?t=112135&page=69 (http://kazus.ru/forums/showthread.php?t=112135&page=69) so I understand that you cut some traces on the PCB, and connect the switches directly to the DTM0660 chip.
I am aware of the APO disable function, but I have found that the LED for RS232 transmit will light up when the instrument is turned off by APO if RS232-function is enabled in the EEPROM. This seems to be a bug, because the LED will use almost the same current (or even more) as the instrument without the LED. Is this bug still present when you use a separate button for Hz/Duty?
-
I think that the photo of a board will explain everything. For operation of this mode it isn't necessary to do any changes in EEPROM. I connected the Hz/Duty button on contacts 31-24.
The RS232 mode isn't necessary to me therefore I didn't include it. :)
-
Thanks, indman. This makes a lot more sense than google's understanding of the Russian language... ;D
I have tried it, and it works fine on the normal ACV function as well as the the extra ACmV function.
I am a little puzzled by this image. It's from the same zip as yours. It seems like they cut one trace? What is the reason for doing so? The translation does not make any sense to me. I have marked it with yellow.
-
Ok!I will try to explain. Ast78512 assigned the Hz/Duty (31-24) function only to the blue button. And it assigned the "Rel/RS232"(19-24) function to one of 4 gray additional buttons. For this purpose it is necessary to cut off the track from contact 19 which goes on the blue button, otherwise it will hinder the correct operation of all functions. :)
After updating of a firmware, technical characteristics of a multimeter look as on a photo :D
-
Thanks again, indman! This makes good sense. It is kind of challenging to grab all the finer details when I have to rely on google translate, especially when the discussion covers several different instruments as in the Russian forum.
I think I have all functions working now, except backlight which I have not tried yet. I will also try to change the RS232 protocol to Volfcraft VC840 as shown. "alvadep" also mention "PC-LINK" as an option for RS232. Is that the software for HP-890CN?
-
No. PC-Link-is a software for a multimeter of HoldPeak HP-90EPC. The most interesting is the fact that else none of owners of HP-890CN managed to include the RS232 mode?! Possibly, this mode is disabled in the DTM0660 processor which is set in this model. And in VC921 the RS232 mode works perfectly. :)
-
If you read the documentation for HY12P66 you will see that the chip is one-time programmable to suit your needs. It is also an RS232 receive function available for programming in addition to the transmit we use. I guess it is meant for a remote controlled instrument.
It seems like Victor saved some money and re-used a chip design from a more advanced instrument.
The EEPROM for VC921 contains current modes, hFE, mV and temperature as functions on the rotary switch as well.
Compare the hex dump shown earlier with this image from the Chinese data sheet for DTM0660.
-
Yes, I agree! I would make in addition some more buttons on the front panel of a multimeter, for example, MAX/MIN,hFe, but is very difficult to find the empty seat in this miniature casing. :D
-
I think you must add some more circuitry and probably make some changes to the rotary switch if you want hFE and current modes. The data sheets show some examples.
Another thing - you have extended the counts to 10000. I have read that the AC/DC converter is a digital signal processor, and that it will fail if the measured value is above ~12000 internal counts. A pure sinus will have 14142 internal counts for 10000 counts AC voltage. This should give that a pure sinus ACV of more than ~8485 counts will show some error. Have you tested this?
-
No, I didn't test in details the ACV mode. I work generally with the mode DCV therefore I was interested in operation on measurement of constant voltage more in case of 10000 counting. Besides it is necessary to remember that there is the known problem of this update - in case of 10000 counting automatic switchings of limits only about 400 Hz correctly work in the ACV mode. If alternating voltage with a frequency over 400 Hz or there are high-frequency harmonicas, then the automatic machine works not correctly. It is in that case expedient to transfer to a manual choice of limits.
-
Inspired by hgg in the UT-210E tread
https://www.eevblog.com/forum/testgear/a-look-at-the-uni-t-ut210e/msg1058296/#msg1058296 (https://www.eevblog.com/forum/testgear/a-look-at-the-uni-t-ut210e/msg1058296/#msg1058296)
I did som testing with an modified and an unmodified VC-921. I used 60Hz sine.
The modifed (8000 counts plus added functions) shows some strange behaviour in the 800mV range (06H). The unmodified instrument has 400mV native. Between about 150mV and 500mV it shows some 5 - 10mV too much, decreasing at higher value.
I have added the 80/800mV ranges as well (02H). No errors there. The unmodified VC-921 did not show any errors in the native 400mV range.
Anyone experienced something like this with their hacked VC-921?
-
A pure sinus will have 14142 internal counts for 10000 counts AC voltage. This should give that a pure sinus ACV of more than ~8485 counts will show some error. Have you tested this?
Hi! I checked operation upgraded (9999 counting) multimeters of VC-921 and HP-890CN in the ACV (mV) mode. From the generator the sine signal with a frequency of 60 Hz is measured. Video can be watched according to this link https://yadi.sk/i/F2N06kz9ybS4v
-
If anybody has a bit of spare time and wants to hack another DT0660 based meter, they might like to take a look at the
http://www.ebay.co.uk/itm/302325367550?_trksid=p2055119.m1438.l2649&var=601161562576&ssPageName=STRK%3AMEBIDX%3AIT (http://www.ebay.co.uk/itm/302325367550?_trksid=p2055119.m1438.l2649&var=601161562576&ssPageName=STRK%3AMEBIDX%3AIT)
http://www.ebay.co.uk/sch/i.html?_from=R40&_sacat=0&_nkw=zt+102+multi+meter&_sop=15 (http://www.ebay.co.uk/sch/i.html?_from=R40&_sacat=0&_nkw=zt+102+multi+meter&_sop=15)
AN8002 also known as the ZT102 and the RM102 and others.
(http://i.ebayimg.com/images/g/sIgAAOSwax5YxkbQ/s-l1600.jpg)
This is actually quite a good value and reasonably robust meter.
It differs from the VC912 in that the pads for the COB are not all broken out, so the pins for the IR serial port may not be available.
https://www.youtube.com/watch?v=HrcxnbkkhYg (https://www.youtube.com/watch?v=HrcxnbkkhYg)
-
Hello all,
I am new to all this software EEPROM stuff and have some questions. I have a VC-921 pocket meter that I would like to change the EEPROM to allow it to be 8000 count and maybe change the auto power off time. I have a Minipro TL866 universal programmer and was able to read the eeprom and get the following. I however don't know what to change to get the above unlocked. Could someone tell me what I need to change and how do you find out what to change and what to change it to when doing something like this.
Thanks
FF FF FF FF FF FF FF FF FF 52 00 FA 00 00 BE 03
A0 0F 68 10 7C 01 6E 50 64 4B 3C 3C 0A FF 40 FF
80 98 F1 81 64 00 96 00 00 80 00 80 00 80 00 80
4E 02 09 58 05 09 1D 04 0B B9 11 0A 7B FF 09 00
00 01 00 01 00 07 98 00 64 00 64 00 64 00 00 00
00 80 00 80 00 80 00 80 00 80 00 80 00 80 00 80
7D 7F 00 83 01 00 81 2A 00 00 00 00 00 00 00 00
08 81 00 80 8A 82 E0 7C 18 01 00 00 00 00 00 00
00 00 00 06 00 00 00 05 00 07 00 0A 12 09 0B 0E
00 00 00 00 00 00 00 0D 00 02 11 0F 00 00 00 15
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0D 00 02 10 0D 00 03 20 20 00 03 20 20 00 03 10
41 00 03 08 41 00 03 05 41 00 03 05 0D 00 02 20
00 80 00 80 00 80 00 80 00 80 00 80 00 80 00 80
3C 7F FF FF FF FF FF FF 5A C7 CC 0F 0F 80 00 00
-
In the datasheet of the chipset is everything you need.
You just need to open a .bin file and change it and reflash the eeprom with the changed .bin file. I cant think of other solutions with a TL866.
It got a VC921 too, and this is where I'm stuck atm....
Sent from my A0001 using Tapatalk
-
Hey guys and gals,
I got my vc 921 to be a 6000 count meter thanks to the data sheet from http://www.kerrywong.com/2016/04/03/dtm0660-datasheet-translated/ (http://www.kerrywong.com/2016/04/03/dtm0660-datasheet-translated/) . It's for the dtm0660 chip that this meter has under that blob. I did try to change the auto off time but it gave me an error when I tried to program the EEPROM. I took a screen shot of the programming changes. changes are in RED. The one red one at the bottom was me trying to change the auto off time. It has the default of 0f.
thanks Rbastler
-
How did you manage to make the changes in the eeprom ? I cant figure out how. Is it possible right with the tl866 ?
Sent from my A0001 using Tapatalk
-
You will need a SOIC 8 dip to clip cable. see photo. You hook up the cable to the ZIF socket on the programmer and clip the other end on the legs of the EEPROM on the PCB. Make sure pin 1 is lined up with pin 1 on the cable. Red stripe is pin 1 on the cable. On the programmer pick Atmel 2402 and hit the read button. Save what you read from the chip to a bin file just in case you mess things up and need to load it back into the chip. Make your changes by clicking on the address you want to change and typing in the values you want. Now push the program button and you should be all set. I got my cable on Amazon for about $10 but I'm sure you can find it on Ebay too. Try a search for SOIC 8 clip programming cable.
Hope that helps. 8)
Good luck.
-
You will need a SOIC 8 dip to clip cable. see photo. You hook up the cable to the ZIF socket on the programmer and clip the other end on the legs of the EEPROM on the PCB. Make sure pin 1 is lined up with pin 1 on the cable. Red stripe is pin 1 on the cable. On the programmer pick Atmel 2402 and hit the read button. Save what you read from the chip to a bin file just in case you mess things up and need to load it back into the chip. Make your changes by clicking on the address you want to change and typing in the values you want. Now push the program button and you should be all set. I got my cable on Amazon for about $10 but I'm sure you can find it on Ebay too. Try a search for SOIC 8 clip programming cable.
Hope that helps. 8)
Good luck.
Yes, that did help ! :-+
Didn't knew you could modifie EEPROM content in the MiniPro software.
I bought a Soic adapter cable, when I bought the VC921 on Aliexpress, so no problems there.
-
Here my successful attempt at modifying the EEPROM for more counts plus a comparison to my Fluke 8050A measuring a quick and dirty AD584 reference:
-
Nice photos of the modified meter in action. I am glad you got it all working. I got mine set to 8000 count as well. I made a how to video if anyone wants to see how its done. DO THIS AT YOUR RISK.
https://www.youtube.com/watch?v=-xFG4pAU3V0 (https://www.youtube.com/watch?v=-xFG4pAU3V0)
Its kind of neat that you can change this stuff!! Fun fun :-+ :-DMM
-
Just wanted to add - Zotek ZT102 has a button placeholder on the back of the PCB called RANGE. It actually works and switches AUTO to MANUAL range mode!
-
This time a really really simple hack. The lead storage for Lab use is silly, so I cut a piece out of the case for the leads. Now I can close the lid without worrying about trying to store the leads.
Youtube short video here https://youtu.be/pQweOiUN2hI (https://youtu.be/pQweOiUN2hI)
-
Hey, I just found that you can enter calibration mode on VC921 by holding REL and RANGE button while it's turned on, switch off and then switch on the meter, it will beep few times while display all the character on the screen then it will enter "CAL" mode with some weird looking character, I worry that I might mess up the calibration of my meter so I switched it off immediately, it still seems fine though
-
Hey, I just found that you can enter calibration mode on VC921 by holding REL and RANGE button while it's turned on, switch off and then switch on the meter, it will beep few times while display all the character on the screen then it will enter "CAL" mode with some weird looking character, I worry that I might mess up the calibration of my meter so I switched it off immediately, it still seems fine though
Didn't work on mine... :popcorn:
-
Hey, I just found that you can enter calibration mode on VC921 by holding REL and RANGE button while it's turned on, switch off and then switch on the meter, it will beep few times while display all the character on the screen then it will enter "CAL" mode with some weird looking character, I worry that I might mess up the calibration of my meter so I switched it off immediately, it still seems fine though
Not on mine.... Afaik you need to short two pads in order to get into cal mode.
-
Somehow I was not able to enter it anymore, the screen blinking with all character and beeping but it never ends.. huh, strange!
edit: sometimes I power it up while holding two button and it only display APO REL but the number doesn't show up, maybe it enter some kind of secret mode?
-
I ordered a Victor VC921 recently (24.05.2018), after i only found offers for the Zotek VC921/Aneng 8203 for a while, which is based on a different chipset/design afaik. I was a little bit afraid that the seller didn't know the difference and that i might instead receive a Zotek/Aneng "clone". To my surprise, i really received a Victor VC921, with the tall numbers on the display and the oval buttons.
But what's really interesting is that it came with the DM1106EN as QFP instead of as COB, just like in my UT210E. Not sure if this changes anything in regard to hackability as all pins seem to be in use anyway, so i guess a COB would have had all pads bonded as well. Still, i prefer this over a COB with (maybe) unbonded pads under the black gunk.
What i don't like is the bend PTC with its bare feet coming quite close to the (i guess) clamping transistors. Solved that with some kapton tape until i have access to my iron again.
Edit: Actually, on a second glance, four pins seem to be unused and could potentially be unbonded on a COB. And sorry that this is more of a teardown post, i have a second unit in the mail that i will hack, once i have access to my tools again, and report here.
-
So, I've needed cheap platform for logging with some degree of safety for some time. After searching, I've found this and similar threads and ordered Victor VC921. Couple days ago the box arrived and I got to work.
Chinese seller sent me different rev. The knob and buttons are a different color, PCB rev. is different too.
EEPROM editing is simple.
Chip is not COB on my rev. it is in TQFP as per datasheet! UART TX pin is small and fiddely to solder a wire to, huge pain in the ass!
To insure some safety I've made IR interface as in datasheet example schematics. But added ring - magnet connection like Apple mag-safe. The IR LED and IR photo-transistor can be salvaged from decommissioned electricity meters/counters(same duty there).
Also I've added input banana sockets and deleted original probes.
Anyway, after I finish the tests, wait for glue and make some stickers - I can take some pictures
-
Thanks everyone for this hack and links and descriptions. I successfully changed my ~7 year old one to 8000 count.
I was unable to change any byte past $0080 (like in the Select multi function table). The programmer would write the earlier changes to the count area ($0010) but would get a verify error on the random things I tried above $0080.
Anyone else experience this? Any ideas why?
On a tangent, I tried to read the 24C02 on my ANENG 8008 and it failed to read at all giving an error during read. Do I need to remove the XTAL or short across it or is it something else? I don't think there are any hacks for it (only the earlier 8002) but wanted to read out the eprom now since I was working with testers.
-
Photos of my dataloging setup, as promised.
-
more photos