Fake VC830L digital multimeter

This article is intended to explain some bad things about cheap digital multimeters since these devices are available in large quantities in Serbia. The key point of this article is security since cheap digital multimeters are not tested/produced according to standards.

VC830L is one digital multimeter available in electronics distribution stores in Serbia, but we will avoid company names, since this article is more about “pay attention before you buy” cheap digital multimeter. The VC830L is about 10 euros, you cannot expect too much, but if you are not able to buy professional digital multimeter which costs over 100 euros, you will certainly buy the cheap one.

Front mask: VC830L digital multimeter.

The part interested for us is security so let see what we actually have regarding VC830L digital multimeter. It has three input connectors, starting from the left side: we have connector for 10 amps, common connector (COM) and the right one intended for voltage, resistance and miliamps measurement. That is all good, it doesn’t have a fourth input to provide more secure measurement by separating miliamps to additional input channel, but we can live without that. What we can see from the figure #1, it is clearly marked that all measurement inputs are protected by fuses. There are two fuses, one between 10 amps input and COM and second one between COM and voltage/resistance/miliamps input. And that is very good, it is a good protection. But, do not believe in these labels until you check is it really secured by two fuses.

Figure#1: VC830L inputs, left: 10 amps, middle: COM and right: miliamps, voltage and resistance input.

When you do open VC830L (figure #2) you will see that there are no fuses inside, more badly there is soldering place intended only for one fuse, and if you want that fuse, that means that you have to spend more money, buy required fuse (in this case 0.2 amps) and do manual fuse assembling (soldering). Who really wants to do that? It is not a problem to spend more money and do some soldering, but I’m expecting that digital multimeter VC830L is protected with two fuses as it is clearly marked on the front of the digital multimeter (figure #1). This is very bad, at the front mask it is clearly marked that protection does exist between inputs, but when you do open digital multimeter you will not find any fuse at all. 

Figure #2: Soldering place for one fuse only, and it is intended for 0.2 amps fuse protection. Look under red rectangle.

Question: where is the second fuse, fuse related to 10 amps input? There is no second fuse! It is completely skipped, removed from the design or? Ok, it looks that VC830L is not actually VC830L by initial design since original digital multimeter VC830L is designed with two fuses, isn't that right? Yes, it is, that is a good question about electrical circuit and which digital multimeter is actually packed inside VC830L case.

One is sure, this is not a VC830L digital multimeter! It is only the VC830L case and that is even more badly. Also, it is not possible to find any of the labels printed on the PCB and it is not possible to find additional information. The conclusion is simple: distributors sell VC830L digital multimeter as VC830L digital multimeter, but it is not VC830L digital multimeter inside! 

It is not possible to find additional printed labels on the PCB about electrical design version or revision.

Anyway, this article is not about distributors from Serbia and Hungary, since the main supplier of these digital multimeters comes from Hungary to Serbia with China origin, but we can only say that this is very bad situation and it could be very dangerous since digital multimeter is labeled with CAT II and that means that we are able to do measurements of 220V 50Hz as it is AC standard in Serbia. It is very important to “pay attention before you buy”! But, how to check digital multimeter against fuses? We can ask a seller is it possible to open the complete multimeter case if there is no additional place for the fuses like there is a place for the battery pack. If there is an additional place for the fuses, that case is simple, just ask the seller to open the additional case and you will see the fuses or not.

The question is: does all cheap digital multimeters includes additional place dedicated for the fuses as for the battery pack? The answer is NO, so ask the seller to open the complete multimeter case if it is possible. If it is not possible, the only way to check fuses before you buy the multimeter, is to search Google and find some articles about multimeter, or ask someone for help. Otherwise, you will never be sure what you are actually buying.

There is only battery pack place, there is no separated place intended for fuses. The only way to check does fuses are included is to open complete digital multimeter pack.

At the end, pay attention, figure #3, digital multimeter is not assembled completely, there are some soldering places intended for diodes which are missing, which lead us to the additional input protection problem, since the diode bridge is used to protect input circuit against high currents before fuse actually start to react. That is also bad for us, but not for the people/services who actually do assembling of these digital multimeters, so it is not bad to check existence of the diode bridge since it is an additional input protection.

Figure #3: diode bridge is not assembled, another protection issue. Look under red rectangle.

Poor soldering quality. It looks that this digital multimeter was not tested against soldering quality after it is assembled. But anyway, this is hand-soldering work and it is very poor in quality.



zilsel-invent assumes no responsibility or liability for any errors or inaccuracies that may appear in the present document. Specification and information contained in the present schematics are subject to change at any time without notice.


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