01 Sep

Ebay LCR meter

LCR meter is something to consider while your lab fills up with stuff to be repaired. Particular a meter with ESR measuring capality is vital. The most common problem with any electrical device is bad cap. Visual inspection usually gives a hint of bad capacitor, more over big electrolytic capacitors have tendency to blow.

Most multimeters have capacitance measurement capability but it does not tell whole truth eg. your measurement may indicate valid value but cap may still be dead. You need to measure ESR. Good thing with most ESR meters is that you can measure ESR while the capacitor is still on circuit. This is possible because the meter does not provide as big voltage level which would light up circuit's non-passives. You may want to check your meter manual if it's suitable for on-circuit measurements.

Price range of handheld LCR meters goes from sub 100 euros to 400 euros and beyond.  Note that not all LCR meters can measure ESR. If you only need capacitance and ESR measurements, Peak Electronics has nice meter to offer (here is review made by Martin Lorton).

If you want quality and accuracy go for well-known brand. Fortunately there exits a cheap meter on the market, DER EE DE-5000, which is accurate and recommended by the hobbyists. DE-5000 also has 100kHz measurement capability which is usually offered by high-end meters (see U1733C vs. U1732C).

So we gave a green light for DE-5000 and after week or so we got this beast



DE-5000 on the right. Size comparison to Brymen multimeter.

DE-5000 on the right. Size comparison to Brymen multimeter.


Pretty much dead already

The meter came with 9 volt battery included so it was ready to take measurements... except it did not start. The battery got very hot right after it was plugged in, which indicated short circuit (no, battery was not backwards whatsoever).

Of course situation like this your first thing to do is take screwdriver and tear it... NO! As faithful customer you contact to your seller and ask for refund or new meter. And that's what we did. In this case, seller wanted to send us broken meter back so he/she could inspect it and send a new one. But before doing that we took it apart...

Now there is your problem

A product with no warranty sticker is real "please look inside me" - sign. So lets take closer look of this meter.

No visual sign of fault. Lets probe some.

No visual sign of fault. Lets probe some.

Not much inside but all you need.  Power management, LCD chip and main custom chip. Layout is neat and clean. First thing to do was to verify short circuit. No surprise here, that is ladies and gentlemen, a top-notch short-circuit.

Class A short circuit

Yep, short circuit

If you follow the red lead you instantly notice that it is connected to R4 and also parallel to (glass) a diode D5. Purpose of this diode is reverse battery protection. See, if a battery is properly placed, the diode just sits there doing nothing since PV-junction is reverse biased; no current flows through it. Shit happens when the battery is reversed, the diode wakes up and let all the current flow through it, hopefully protecting rest of the circuit and eating your battery in a blink of an eye. Problem was, the battery getting hot even it was correctly placed (getting hot, current flows).


Measuring diode D5

According to other diodes, voltage drop is about 0.5V for each diode. D5 gave something else, no matter which way measured.


Shitty diode.

Measurement makes sense and fits nicely into context. The diode is dead and it is shorted in every possible ways making meter useless. Changing the diode would have been easy solution indeed, but whether damage already happened to the rest of the circuit, we did not know and we did not care since we shipped it back to seller and got a new one.


Even with negative experience with the first candidate of the meter, it still is decent meter. The new one works great and measurements seems to meet the specs. But like we said earlier, if you want quality, go for well-known brand.