Question about VC8145-Newbie - Page 1
Forum section: electronics / testgear

author: nadona
author_rank: Regular Contributor
timestamp: November 21, 2012, 07:04:17 am
content: Hi everyone,I'm just beginning learn electronics and I am in the process of setting up my lab.I already had a $20 multimeter, so I decided to get a bench DMM and I might buy a better handheld. The bench type is the VICHY VC8145, and I am still thinking about the handheld. (I have the UNI-T UT-61E in mind.)Here is the question I am having with the VICHY.The problem arises whenever I measure higher than a DC 8.2 V. When I touch the probes a number shows up for a split second, and then there is 0L with a "beep beep beep" for about two seconds. After that it displays the value. If I measure something less than 8.2 V though, the screen displays the number with no delay. If I very slowly increase the voltage from this point higher than 8.2 with the probes still touching though, there is no problem.Is this problem easily fixed?I just bought this brand-new on Ebay from Shenzen, China, if that helps. If I cannot fix it, then I have to return it. But I'd rather just fix it if that's possible.Thanks in advance!

author: iloveelectronics
author_rank: Frequent Contributor
timestamp: November 21, 2012, 07:29:44 am
content: That sounds normal. It's a 80,000-count meter and at 8.2V it's auto ranging from the 8V range to the 80V range. It probably just has a slow auto ranging speed, hence the beeping (for overloading the lower range) before it reaches the correct range.

author: nadona
author_rank: Regular Contributor
timestamp: November 21, 2012, 07:58:09 pm
content: Is that what you think? Thank you!I'd like input from the owners of this same model. Does the same thing happen to them too?

author: ziplock9000
author_rank: Regular Contributor
timestamp: January 12, 2017, 01:48:51 am
content: Quote from: nadona on November 21, 2012, 07:58:09 pmIt happens to me, seemingly all the time. It often doesn't find 11.70v for example and will just continue to beep.

author: nctnico
author_rank: Super Contributor
timestamp: January 12, 2017, 11:22:40 am
content: Mine also beep when the voltage or current measurement switches to a higher range. It doesn't do that when measuring resistance or capacitance. Maybe it is some kind of warning for the user that the voltage or current is suddenly much higher.

author: Wytnucls
author_rank: Super Contributor
timestamp: January 12, 2017, 11:33:44 am
content: More likely to be a defect with the meter.Some meters have a proper warning on the screen when voltage becomes dangerous, being higher than 30V.

author: nctnico
author_rank: Super Contributor
timestamp: January 12, 2017, 12:49:57 pm
content: Quote from: Wytnucls on January 12, 2017, 11:33:44 amNo, it definitely is not. It is the way the VC8145 meters work! I can't say I like it but it is something you have to live with or buy a different meter.

author: pascal_sweden
author_rank: Super Contributor
timestamp: January 12, 2017, 01:04:30 pm
content: Why not file a firmware change request to the manufacturer?

author: Wirehead
author_rank: Regular Contributor
timestamp: January 12, 2017, 01:17:28 pm
content: Not firmware upgradeable, these units. Baked in.

author: Wytnucls
author_rank: Super Contributor
timestamp: January 12, 2017, 01:22:30 pm
content: More of a design flaw, but in the case of ziplock9000, if it can't display certain voltages, it is an unacceptable defect.

author: janoc
author_rank: Super Contributor
timestamp: January 12, 2017, 02:26:11 pm
content: I would also say it is a design flaw, reviews of this meter are full of complaints about the annoying beeps. Vichy is not exactly known for quality instruments - it is really the bottom of the barrel stuff built down to a rock bottom price, so corners are shaved everywhere. Your meter has been discussed on this forum before:https://www.eevblog.com/forum/testgear/vc8145-thread-it's-here-finally/I don't know how much you have paid for your meter, I have seen them sold for about $100-$120 online. However, you can often find an older HP/Agilent 34401a 6 1/2 digit bench meter on eBay, for example (or one of the more recent models). I have recently managed to score one for 200 EUR in perfect shape, with still valid calibration, only the display was a little dim from the years of use, but that was easily fixed. Those are time proven quality instruments built like a tank, with well documented service procedures and much better value than anything coming from Vichy, IMO. Especially if you actually need the accuracy of a bench meter and aren't buying it only to avoid having to replace batteries in a portable one.

author: nctnico
author_rank: Super Contributor
timestamp: January 12, 2017, 02:47:12 pm
content: Sorry but I have to strongly disagree. The VC8145 beats the 34401A hands down when it comes to features (20A current measurement, capacitance, big backlit display, temperature probe included, instant continuity test, dual display). The 34401A is only nice if you need the accuracy but for a daily driver bench DMM the VC8145 is just more comfortable and versatile. I also have a Keysight 34461A DMM but I almost never use it because of the fan noise and the slow startup.

author: doktori
author_rank: Newbie
timestamp: January 12, 2017, 03:10:32 pm
content: Yeah it's normal. You can always use the RANGE button to turn off the auto-ranging and it will read much faster.

author: ziplock9000
author_rank: Regular Contributor
timestamp: January 13, 2017, 07:57:47 pm
content: Quote from: Wytnucls on January 12, 2017, 01:22:30 pmIt's a bit hitty missy as to when and if it gets "stuck"..

author: ziplock9000
author_rank: Regular Contributor
timestamp: January 13, 2017, 07:59:17 pm
content: Quote from: doktori on January 12, 2017, 03:10:32 pmThis is what I sometimes do when it gets stuck. It's not too much of a pain.

author: janoc
author_rank: Super Contributor
timestamp: January 13, 2017, 09:21:23 pm
content: Quote from: nctnico on January 12, 2017, 02:47:12 pmDon't know about 34461A, but 34401A starts pretty much instantly (of course, you should let it warm up for best accuracy) and has no fan, so no noise apart beeps and relays clicking. Yeah, no temperature, no capacitance range and current only up to 3A, but that is not really what I have bought it for.Your requirements are usually not why most people buy a bench meter, but fair enough. However a newbie building up a lab would be probably much better off with a decent portable meter than the Vichy bench meter for those features.

author: nctnico
author_rank: Super Contributor
timestamp: January 13, 2017, 09:29:25 pm
content: I really don't get why a bench meter should be accurate. Who got that daft idea? Hand held meters are terrible for bench use because they (typically) have auto-power off and run out of batteries. Also visibility is poor unless you use a tilt stand (which probably hides another instrument) and you can't stack them.

author: janoc
author_rank: Super Contributor
timestamp: January 15, 2017, 06:43:35 pm
content: Quote from: nctnico on January 13, 2017, 09:29:25 pmI would say that for a 6 1/2 (or more) digit class meter accuracy would be the design objective. Otherwise nobody would pay that sort of money for it.Quote from: nctnico on January 13, 2017, 09:29:25 pmFair enough. I still wouldn't consider getting a bench meter for these reasons (takes as much space as 3 handheld meters, you can get portable ones with nicely readable displays too), especially from a company like Vichy, but everyone has own preferences.

author: nctnico
author_rank: Super Contributor
timestamp: January 15, 2017, 06:59:36 pm
content: Quote from: janoc on January 15, 2017, 06:43:35 pmWhy does a bench meter need 6 1/2 digits?BTW space is different than volume. Put a serious amount of equipment on a bench and you'll notice that a handheld DMM takes an awfull lot of space because you can't stack something on top of it and it sits in front of displays / controls of other equipment. Been there done that.

author: Wytnucls
author_rank: Super Contributor
timestamp: January 16, 2017, 06:53:34 am
content: Bench meters are very different from handheld ones, hence costly.They are usually meant for professional lab use, with GPIB connections, much higher crest factor detection, high bandwidth, 4 wire resistance measurement, external trigger, extended statistics and math functions and, most importantly, very high sampling rates.Probe jacks are provided at the rear of the instrument, to avoid the mess of cables in front of knobs and displays, in a professional set up.The Vici, like some of the Uni-T meters, is basically a handheld meter PCB, fitted in a box for the convenience of stacking and mains connection. It shouldn't be compared to legacy bench meters.

author: ziplock9000
author_rank: Regular Contributor
timestamp: January 16, 2017, 07:36:27 am
content: Quote from: Wytnucls on January 16, 2017, 06:53:34 amWhat you've described there is fairly high-end bench meters and what you said subsequently implies that ONLY high-end meters can be bench meters. This is of course absurd and smells very much of elitism rather than practicalities. Like everything else there's entry level, prosumer, pro and consumer versions of products. My personal opinion is if it's form factor is designed for your bench and it has mains power, it's a bench meter. It's capabilities are of secondary importance to the label "bench meter". The Vici for it's price bracket has some good features and accuracy.

author: Wytnucls
author_rank: Super Contributor
timestamp: January 16, 2017, 08:29:47 am
content: What I have described is the majority of current good quality bench meters.Fairly recently, some top manufacturers tried to make some of their instruments more affordable, like the Fluke 45 and the Keithley 2110, with reduced capability, with mitigated success.Some Chinese companies improved further on that attempt, deciding like you do, that a square box format is all that is required, even if you have to push a button indefinitely to keep the display lit.They figured they could charge a premium for that format, riding on the coattails of main stream manufacturers.

author: nctnico
author_rank: Super Contributor
timestamp: January 16, 2017, 10:26:36 am
content: Quote from: Wytnucls on January 16, 2017, 06:53:34 amLegacy bench meters like the 3.5 digit Fluke 8012A or the 3.5 digit HP 3435A??? Sorry but your idea of a bench DMM is completely wrong! If you bothered to look up teardown photos of the VC8145 you'd see the PCB has been designed to fit the bench DMM case and it has not been designed to be low power. So please no nonsense about fitting a handheld DMM PCB in a case because that just isn't true.

author: Wytnucls
author_rank: Super Contributor
timestamp: January 22, 2017, 12:14:13 pm
content: You couldn't have picked worst meters to characterize legacy bench meters, but then objectivity has never been your forte.Those two portables can both be powered from an internal battery. Fluke, which was only a two-bit player in the '70s bench meter market, actually called them 'bench like' portable meters. Look it up!Of course the PCB fits the enclosure, but that doesn't prevent the architecture to be close to a portable DMM, with a Fortune ADC with APO, low battery detection, low sampling speed, low power consumption and with a 9V feed for a battery. It also has a backlight button for the LCD.For the uninitiated, here are some of the best current and genuine legacy bench meters:Fluke 8846A 8845A 8808A 45 8842A 8840A 8860A 8506A 8505A 8502A 8520A 8400A 8375AAgilent 34401A 34405A 34470A 34465A 34461A 34460A 34410A 34411A 34450A U3402A 3478A 3468A 3458A 3457A 3456A 3455A 3490A 3450Rigol DM3068 DM3058 DM3058E DM3061 DM3051Keithley 2002 2001 2010 2015THD 2016THD 2000 2100 2110 199 197A 196 195A 193ATonghui TH1961 TH1951 Tektronix DMM4050 DMM4020Hioki 3239 3238 Advantest R6871E R6551 R6441B R6848 R6846Yokogawa 7562-01 7555 R&S Hameg HMC8012 UDS5 Thurlby 1905 1906Racal Dana 5006 6002 Solartron 7151 7150 Guildline 9578 9576 Datron 1271 1071 1062 1061ADCMT 7461P 7461A 7352A 7451A Iwatsu 7602 7522 Prema 8017 6048 6047 6040S 6030 6001 5017 5000Siglent SDM3055 Picotest M3500A M3510A

author: nctnico
author_rank: Super Contributor
timestamp: January 22, 2017, 12:49:04 pm
content: Sorry but insisting a bench DMM must be accurate or has to contain more than one PCB just isn't realistic. I call it BS unless you can show some law of physics which says a bench DMM should have at least 6.5 digits or more and have certain parts inside. Oh and which DMM on that list can handle 20A?

author: Wytnucls
author_rank: Super Contributor
timestamp: January 22, 2017, 01:28:44 pm
content: I never said a bench meter should have at least 6.5 digits, but these days most do, as the technology gets cheaper. Accuracy goes hand in hand, whether you need it or not.20A on a bench? What do you deal with? Hadron colliders? Equipped with a 13A medium blow British BS1632 fuse, a limit of 15 seconds and an accuracy of a few %? You must know that a lot of cheap DMM manufacturers often boast about that feature.I am surprised you even brought it up, as most professionals would rather connect a safer current shunt to measure anything above a few amps.That said, if on a budget and can get by with portable DMM features in a stackable box, the Vici is for you, but be aware of all its warts.

author: nctnico
author_rank: Super Contributor
timestamp: January 22, 2017, 03:58:10 pm
content: Every now and then I get projects involving power electronics and having some headroom over 10A (which is a nice round number to write in a specification) has proven to be beneficial. I'm aware of the time limits of the high current measurements capabilities but it is a convenience thing. Mostly I need to measure the current to check if the current read back of a circuit is within tolerance (usually worse than 1% accurate) or to measure efficiency. Both these measurements don't take longer than a few seconds.I wouldn't call a current shunt (typically without enclosure) safer. Putting a shunt in the 0V (low side) prevents me from hooking the ground clip of a scope in various places or connect other grounded equipment (like a PC). Also a shunt may become open (due to a fuse or whatever) which could wreck a whole lot of equipment if it turns out there is a ground loop after all (*). Therefore in my test setups I generally want one central grounding point which is 0V so I (typically) measure currents in the supply line (high side) which in some cases can be (way) over 48V. A shunt which is out in the open would be dangerous to touch and have an extra bunch of leads coming from it to a DMM. The DMM would also need to be able to convert the voltage reading into a current reading. All in all a DMM with a high current capability brings everything conveniently together in a safe-to-touch box and if the shunt burns out then it does so inside a box and not out in the open.(*) Some of the testing I do involve power supplies capable of delivering several kW of power which can do a lot of damage. This relay contact for example just melted away because of arcing:

author: Wytnucls
author_rank: Super Contributor
timestamp: January 22, 2017, 09:55:41 pm
content: Most people won't need them, but there are enclosed shunts, like the one below, made by Fluke (30$ second-hand).Direct connection is more convenient, but the problem with high current through the meter is that it could damage the internal shunt permanently, if the shunt temperature exceeds 120 degrees C, compromising further readings.The feature Y=mX+b is fairly common on bench meters. Both of my cheapish bench meters can easily do the V/I conversion (Rigol 3058E and Keithley 2000)You're still left with the ground loop problem though.http://www.ebay.ca/itm/Fluke-80J-10-10-Amp-100-mV-20-Amps-25-Accuracy-DC-to-10-kHz-Current-Shunt-/222031485558?hash=item33b21b9a76:g:9ysAAOSwezVWy3Ny