VC8145 thread ... It's here, finally

[EEVblog]

Guys, stop the slanging match now, or the thread gets locked.

Dave.

[Wytnucls]

I'm done. My apologies to Dave and others who are still reading this thread, but I had to get it off my chest.

[SeanB]

I bought a UT81B this weekend ( second owner) and am pretty happy with it. Nice little addition to the toolbox, and has come in useful already. Yes, has drawbacks, but I am still learning how to use it and what it's capabilities are, but so far very nice and usable. Nice big display in meter mode is a nice plus for viewing, and I did use the hold mode in scope mode already as I ran out of hands and used a pinkie to press the hold while holding probes in the circuit in question.

[nctnico]

I'll try to take a stab at a review:

I think I already made clear in this thread what I want from a bench multimeter so I won't go into that again. The VC8145 offers many features besides just measuring volt, current and resistance. It can measure capacitors, frequency, RPM,  duty cycle, diodes and temperature. As an extra bonus it is also capable of generating a square wave with adjustable duty cycle. The frequency of the square wave is selectable from 16 frequencies between 0.5Hz and 5kHz.

It has a dual display so it can display two values at once. At the bottom of the screen there is a bar-graph which gives a quick indication of the measured value. For instance it can display both DC and AC components in the volt and current modes but also the frequency when selected. The 2nd view button controls what is in the secondary display at the right top of the screen. In temperature mode it shows both Celcius and Farenheit. There is something odd about the temperature mode though. When pressing the 'TEMP' button it apparantly shows its internal temperature (which is supposed to be the room temperature). You need to press 'select' for the meter to use the external temperature probe. This tricked me into thinking the temperature probe that came with the meter was broken.

When measuring AC it can also display the values in dBm with a large selection of reference resistances ranging from 4 Ohm to 1200 Ohm including 50 Ohm, 75 Ohm and 600 Ohm which are often used.  Other neat features include auto-hold and positive and negative peak hold. Most advertisements say the meter has an isolated serial port but you actually need an extra adapter which provides the isolation and RS232 interface. Talking about adapters.. the input bushes are spaced according to the 'standard' distance so they accept a 4mm 'banana' plug to BNC adapter.

Overall the designers of the VC8145 did their best to pack as many usefull en less usefull features they could think of into an affordable bench multimeter. I think they came up with a very complete product. I always like equipment where the engineers clearly got some say in the product specifications.

I own the VC8145 for over a year now and I must say I don't regret buying it. It has become my preferred DMM. It defaults to autoranging but the autoranging is not as slow like on some hand-held meters. The autoranging works faster than having to press a range button. The casing doesn't have rubber feet so it tends to slip away. Some stick-on feet solved that problem. Furthermore the meter likes to beep a lot. It beeps when it is switched on, when you press a button and when it needs to make a big switch in range. The probes that come along with it are just standard el-cheapo probes. I use these probes which are much better for probing around in SMT circuits:
http://uk.farnell.com/hirschmann-test-measurement/pms0-64-smd/test-kit-micro-60v/dp/1011414

[Rick]

I bought a UT81B this weekend ( second owner) and am pretty happy with it. Nice little addition to the toolbox, and has come in useful already. Yes, has drawbacks, but I am still learning how to use it and what it's capabilities are, but so far very nice and usable. Nice big display in meter mode is a nice plus for viewing, and I did use the hold mode in scope mode already as I ran out of hands and used a pinkie to press the hold while holding probes in the circuit in question.

Can you plug it into the wall socket and visualize the mains voltage in the oscilloscope mode?

[SeanB]

Why would I want to do that? I have a perfectly good set of other CAT3 meters to do that with.

[Rick]

To visualize the waveform for example. Somebody was talking a few days ago about sending a modulated carrier through the mains. I have in the past done a small such project. In which case if you want to inspect what is being sent to the other side of the transformer, it would be very useful, wouldn't it, see the amplitude etc.
If you pay an extra $60, you can get the cheapest UNI-T which has a better screen I believe. But somebody was saying one channel handheld scopes are useless...  the 2 channel ones cost at least $500. What is your opinion?

[SeanB]

If I do that I will use an external 10X capacitive divider to drop the voltage, as it will be safer for me to work with. In most cases i will be using it for low voltage work, where it has good utility. May be rated to 1000V but I still need to check the calibration, it overreads by 1 digit on 10V, showing 10.01V and is quite linear about it, 20V shows 20.02V

[T4P]

The probes that come along with it are just standard el-cheapo probes. I use these probes which are much better for probing around in SMT circuits:
http://uk.farnell.com/hirschmann-test-measurement/pms0-64-smd/test-kit-micro-60v/dp/1011414

Yeah, the probes are pretty crappy. I think i mentioned this but again i might have forgot, i had some probes i got for about 5~6SGD that are miles better than the probes supplied. Not a problem, i'll always throw crappy probes into the bin

[iloveelectronics]

I usually keep the leads just so I have some spare thick-ish wires to use for some projects

The probes that come along with it are just standard el-cheapo probes. I use these probes which are much better for probing around in SMT circuits:
http://uk.farnell.com/hirschmann-test-measurement/pms0-64-smd/test-kit-micro-60v/dp/1011414

Yeah, the probes are pretty crappy. I think i mentioned this but again i might have forgot, i had some probes i got for about 5~6SGD that are miles better than the probes supplied. Not a problem, i'll always throw crappy probes into the bin

[T4P]

I usually keep the leads just so I have some spare thick-ish wires to use for some projects

The probes that come along with it are just standard el-cheapo probes. I use these probes which are much better for probing around in SMT circuits:
http://uk.farnell.com/hirschmann-test-measurement/pms0-64-smd/test-kit-micro-60v/dp/1011414

Yeah, the probes are pretty crappy. I think i mentioned this but again i might have forgot, i had some probes i got for about 5~6SGD that are miles better than the probes supplied. Not a problem, i'll always throw crappy probes into the bin

Actually that's what i do  But damn, 1 star rating -facepalm- It's all thanks to wytnucls for derailing the thread

[Wytnucls]

The truth does bother you quite a bit, doesn't it?
Let's see who derailed the thread, with personal attacks:

[Wytnucls]

Dave or Simon, please lock this thread, there is nothing to see here. We're not going to get an impartial review of this meter anyway. 

[Monkeh]

The truth does bother you quite a bit, doesn't it?
Let's see who derailed the thread, with personal attacks:

Personal attacks? Okay, we clearly have a very different definition of personal attack.

[ales22]

This thread is pointless from 2nd post, where all can see that this meter (and all cheap benchtops, Uni-T incl.) is handheld guts put in large plastic box with mains transformer. This fact implies all cons and pros discussed here. Someone finds all cons negligible and is very happy with that meter, someone won't buy just for only one reason. That's my case too, because my workbench is 0.6x0.9 meter, I can't waste space with fresh air packed in plastic box. I would go for handheld. But it doesn't mean that this meter is not good. It's not good for me.

[Rick]

There are 5 1/2 digit bench multimeters out there on ebay, for example the much praised HP 3478A for $150, I would buy one of those rather than the VC8145.
Of course you need to find the right seller (there are some) who has the device you want and not the crook who tries to pass his faulty device off on you as a good one ( I tried this verb for the first time I hope it is ok). Hey at least I improve (or I have the impression that I improve) my English here
Seriously having seen other people trying to repair their stuff is really dissuasive for us abroad. You pay lots of money for shipping and the guy sells you a crappy multimeter. You have to pay about the same amount to return it to USA. This is too much to bear.

[nctnico]

What multimeter you buy is up to you. All I'm saying is that people should give an unknown brand a try. Chances are that equipment for Tektronix, Agilent, Lecroy, etc is rolling of the same production line or designed by the same people. Anyway, I've taken some pictures of the inside of my VC8145:
The rear with the 'RS232' interface, power supply and transformer


The front:


A close-up of the inputs. I like the inputs bushes are not soldered onto the PCB but use screws (with a spring washer). Soldered bushes often give problems in the long run.


An overview of the display board with a Holtec 8 bit microcontroller and what seems to be a display controller:


The 'RS232' plug on the back seems to be isolated after all.


Here is the analog board without the shielding:


On the analog board there are several hybrid resistor ladders, a special chip and some regular stuff like an LM385 1% reference and a 12bit DAC. The DAC is interesting because it is relatively expensive costing more than $5 even when bought in large quantities. The designers clearly didn't cut a corner here.


Furthermore there are some relays from Omron and two HC4053 analog muxes from ST


Edit: moved pictures to Flickr

[nctnico]

Seriously having seen other people trying to repair their stuff is really dissuasive for us abroad. You pay lots of money for shipping and the guy sells you a crappy multimeter. You have to pay about the same amount to return it to USA. This is too much to bear.

Buying second hand test equipment is a bit of an art. If you want to buy something you need to check for known problems on forums like these. Also be sure to check the feedback when buying from Ebay. Actually most sellers from the US don't try to sell you crap because they don't want the fuss. If they don't know how to test it they are honest enough to sell it 'for parts'. Asians OTOH are very prone to sell bad used equipment. The prices usually are very reasonable but expect some hidden surprises!

[Rick]

Ok thanks for the good advice.
Right, especially stuff from a few sellers from Singapore seem dodgy to me, I don't know...
And when you buy from China it's better to buy new equipment of course.
Shall you make some measurements with that VC8145?
We don't have the possibility to go and pick up stuff ourselves like T4P, so... and shipping old stuff from Singapore and China is as expensive as shipping from USA.
Recently I have discovered that shipping by sea from Australia is very interesting but it takes up to 3 months for the items to arrive...
Actually I am fairly sure some sellers from USA know well their devices are no good but prefer to stay on the safe side by saying "for parts or repair" just in case the buyer would complain to ebay.
Generally speaking if the seller does not answer specific questions, it is better not to buy. People who don't know how to run basic tests should not be allowed to sell such items.
You say "could you please measure the voltage of a 9V battery, a resistance and the mains voltage" and you hit a wall of silence.
Obviously there is something wrong out there:)
On the other hand you have US sellers who make videos of the self test sessions or provide the pics of measurements. These are the rare good ones. I missed the opportunity to buy a Fluke 8840a from such a guy. It was quite cheap.
I mean generally buying on internet is a risk, we cannot accuse specifically US sellers, I talk about them because Fluke instruments are mainy sold in USA. We have plenty of crooks here on our local equivalent of ebay. If you are lucky you buy from the good guy but the others hide the faults of their devices.

[grenert]

On the analog board there are several hybrid resistor ladders, a special chip and some regular stuff like an LM385 1% reference and a 12bit DAC. The DAC is interesting because it is relatively expensive costing more than $5 even when bought in large quantities. The designers clearly didn't cut a corner here.

What is the DAC chip you see, and what is the multimeter doing with the DAC?

[rsjsouza]

I've taken some pictures of the inside of my VC8145:

Thank you for the time to put both the information and the pictures together... Plowing through the noise I really enjoyed finally seeing some info related to the actual equipment. 

What is the DAC chip you see, and what is the multimeter doing with the DAC?

I guess it is the SOIC-8 AD739J device. Maybe I am misreading the part marking, but I could not find an AD739, but instead an AD7390 (12-bit) or an AD7391 (10-bit) with the same package...

[Monkeh]

What is the DAC chip you see, and what is the multimeter doing with the DAC?

I guess it is the SOIC-8 AD739J device. Maybe I am misreading the part marking, but I could not find an AD739, but instead an AD7390 (12-bit) or an AD7391 (10-bit) with the same package...

No, that's an AD737J.

[rsjsouza]

No, that's an AD737J.

You are probably right, but oh boy, I must be getting blind...  I still can't see a seven there, but per the device description (TRMS-DC converter) it surely pertains to a DMM. Thanks!

[Monkeh]

No, that's an AD737J.

You are probably right, but oh boy, I must be getting blind...  I still can't see a seven there, but per the device description (TRMS-DC converter) it surely pertains to a DMM. Thanks!

Your eyes are fine, it's just a terrible picture of a dirty IC. More megapixels does not mean you can skimp on good optics.

[rsjsouza]

Your eyes are fine, it's just a terrible picture of a dirty IC. More megapixels does not mean you can skimp on good optics.

this is our current world of built-in cameras...