VC8145 thread ... It's here, finally

[gatoazul]

Do you Know whats the reference voltage used in VC8145 (Chip?)
?

[nctnico]

It seems I took one of mine apart 4 years ago:
https://www.eevblog.com/forum/testgear/vc8145-thread-it's-here-finally/msg174988/#msg174988

I re-uploaded the pictures today because Imageshack has stopped.

[torch]

Mine's been powered up 24/7 for about a year now and it seems to be as accurate as when I got it. Not that I have a Keysight to check it against or anything. (I've been meaning to buy one of those inexpensive calibrated voltage standards. Maybe it's time to toddle off to eBay). But comparing voltages to other volt meters and frequency measurements against my faithful Rigol, I don't think it wandered very far. Even the on-board square wave generator seems to be on the money, which would be great if it wasn't limited to 5KHz  .

I really like the large, clear, easy to read display.

[ziplock9000]

@ k2teknik :
Hello, thanks a lot for suggestion!
The UT70D software runs well and i's good enough for a common use.
It's a pity for the wrong position of decimal point, as You said.

Do you have a link to it please?

[k2teknik]

Do you have a link to it please?

Try https://drive.google.com/drive/folders/0B4Jyby-tjH5oMkdsX0pGT2piZkk
I did not test any of these, but the link is from Uni-T them self http://www.uni-trend.com/productsdetail.aspx?ProductsID=600

[pascal_sweden]

It seems I took one of mine apart 4 years ago:
https://www.eevblog.com/forum/testgear/vc8145-thread-it's-here-finally/msg174988/#msg174988

I re-uploaded the pictures today because Imageshack has stopped.

Do you have more than one? How many?

[nctnico]

I have two and I'm thinking of getting one or two more but that depends on whether I can score one or more of the GW Instek DMMs from the ITT auctions. Sometimes I need more DMMs in a test setup.

[torch]

Hi,

im interested in this meter.
How is it going over this years in terms of accuracy?
Could someone who owns this bench multimeter do some accuracy tests?

I'm sorry it took so long, but I ordered this reference module on eBay and it just arrived yesterday. Vendor claims it is measured with a calibrated HP3458A and provides calibration data indicating the actual outputs are 2.50175, 5.00392, 7.50688, and 10.00845 vdc.

I measured the 2.5, 5.0, and 7.5 v outputs 3 different ways: Auto, Rel and manually increasing the range one step.

So, for the 2.50175 vdc standard output, the VC8145 measured:
2.5013 (auto)
2.5022 (rel = -0.0008)
02.500 (manual range)

for 5.00392 vdc standard output:
5.0038 (auto)
5.0046 (rel = -0.0008)
05.002 (manual range)

for the 7.50688 vdc standard output:
7.5069 (auto)
7.5077 (rel = -0.0008)
07.505 (manual range)

The 10.00845 output measured 10.007 in auto and 10.006 in manual, although the rel read 0.

I have had this meter well over a year now and it is generally left on.

Edit: so DCV accuracy works out to +/- 0.02%. Spec is +/- 0.05%+5, so mine is in spec on that range, anyway.

[k2teknik]

I checked my VC8145 vith a reference module from eBay too and I cheked all my multimeters, my best one is a Solartron 7150 so I show that one just for a reference.
So my VC8145 is not within spec and that is ok with me, on the other hand I had not seen any drift too.

VoltReference  Solartron 7150            VC8145
  2,50124          2,50152  -0,011%      2,5031 -0,074%
  5,00253          5,00307  -0,011%      5,0068 -0,085%
  7,50426          7,5051    -0,011%      7,5109 -0,088%
10,00489        10,00595  -0,011%    10,014   -0,091%

[mentaldemise]

Could someone provide an image of the CD with the VC8145? I got mine today but the CD is bad so I can't install the app to use the RS232 interface.

[mentaldemise]

Nevermind. I left the house for 2 hours, returned, and now it won't display anything and the beep is muted. Time for a return.

[k2teknik]

.. now it won't display anything and the beep is muted. Time for a return.

Had you try to disconnect the power, wait a minute, reconnect power and then turn it on?
It is a Chinese designed unit sometimes it do strange things.

[sn4k3]

My VC8145 temperature function never worked. It shows only current temperature i think.
I test with other probes as well.
Anyone have this issue? I have done the backlight ON mod

[coromonadalix]

hi @ll   is there a known calibration procedure for these meters ?

[nctnico]

My VC8145 temperature function never worked. It shows only current temperature i think.
I test with other probes as well.
Anyone have this issue? I have done the backlight ON mod

You have to press the select button to toggle between internal and external sensor.

[sn4k3]

My VC8145 temperature function never worked. It shows only current temperature i think.
I test with other probes as well.
Anyone have this issue? I have done the backlight ON mod

You have to press the select button to toggle between internal and external sensor.

Dam that's did the trick. Thank you 

[ultrablog]

Hi

I think my Vici 8145 developed a problem. I wonder if there's a reset procedure or some known issues?
I don't think I should send it in for repair, it came from china and it's a few years old, so very doubtful that is a good idea. The shipping would kill me, and with no guarantee to see it back repaired...

Most of my ranges work. VDC, VAC, mV, mA, 20A, Ω all seem fine. The button for backlight too. But the other buttons adjacent to those react weird. They beep, and the mode changes, so it's not that the button is dead. But the functions are fubar. For example, selecting temp mode displays Ω in the display. Selecting capacity displays mV, and so on. It's erratic. Sometimes it also goes wild beeping. I'm having trouble so determine when that happens if it goes berserk or that it switches ranges continually.

This post is twofold... in a way to warn people, but hopefully someone has a good tip to try and reset it to its working order again...

[nctnico]

Perhaps check the ripple on the power supplies. Or the rubber mat with the bushbuttons got dirty and needs to be cleaned. It could be a bad solder joint too; shouldn't be hard to find if you follow the connections to the keypad.

And if you think this is a problem for cheap Chinese products: I had a similar problen on a >$20k Lecroy scope where it turned out a whole bunch of diodes in the front panel switch matrix where broken because they used a diode which is unsuitable for the purpose.

[coromonadalix]

Does anyone made a eeprom dump ??   wanna check something ...

[MBY]

One thing I HATE about this meter: It beeps loudly anytime, anywhere. Several beeps on boot, beeps on every button press, beeps on ranging.
One thing I like about this meter: Even if the continuity beep isn't latched, it's fast and loud.

Removing the buzzer or wrap it in something doesn't cut it, because I want the loud beep when doing continuity.

Solution:
Turns out that the relays are high-side switched and in diode/continuity mode, only the relays K1 and K3 is activated. The other modes has other combinations, but K1=on, K2=off, K3=on, K4=off seems to be unique for this mode. So a simple diode AND-function could be used to only enable the buzzer in the diode mode. The buzzer rests at +6.66V and the relays are 5V-driven with respect to ground. So the LED is to avoid that current from the 6.66V rail (or whatever it is) creeps into the 5V circuits. Any red or green LED with a forward voltage of about 1.6-2V should do it. I don't think the component values are critical in any way. 1N400X or 1N4146 is probably fine, or even two LEDs for the "AND" (negating the need for the pull up LED). I just happened to have 1N5819 schottkys. The buzzer is dynamic, so no need for a "return path" or relying on the implicit back diode in the 2N7000, so a bipolar transistor will probably also work just fine.

If you want a quiet beeping in the other modes, just parallel the DS on the transistor with whatever resistor feels right (the buzzer is 16 ohms).


Here is the back side of the analog PCB. There is no need to remove the shield as the relay is accessible from the back side. Don't mind the blue LEDs, I just mounted them there in order to see which relays were on in which modes.

...and here is the "ghetto mod" itself.

It work very well, the buzzer is off in all modes except for diode/continuity. The instrument even "feels" more professional, as you now hear the relay switching when you change modes, something that the buzzer shouted down before.   

Edit: So the "embedding" of the pictures didn't work. Sorry if the context got messed up, but you have the pictures below.
Edit2: Do'h! Naturally I misspelled "marked" in the schematics as "maked". Another thing to note, is that the buzzer itself has a +-marking and as far as I can tell, it was mounted backwards on the PCB. And yes, I damaged the plastic of the buzzer with my soldering iron as you see in the pictures... 
Edit3: Clarification: The "positive terminals" on the relays refers to the *coil*, not any of the contacts.

[Microcheap]

Thanks for sharing. I will definitely have to try that mod.