Capacitance checker


ESR Meters… Is there something better than the MESR-100, or is it the Bee’s Knees (for the price)?

See also


MESR 100

I first saw the MESR-100 (along with the Fluke 12) in this annoyingly loud video, 3 Ways to Check Capacitors in Circuit with Meters & Testers, turn the volume down before clicking. It has a micro USB charge/power port.

On Stack Exchange the answers and comments to these questions poo-hoo the device somewhat, or rather the concept of in-circuit testing:

EEVBlog breakdown,

Unfortunately, one of the main issues is that the MSR-100 only checks using a 100 KHz test signal, which is not the same frequency at which electrolytic capacitances are specified, which is 120 Hz (the frequency of a fully rectified US mains wave). Other meters often allow the frequency to be changed.

However, that said, it is primarily an ESR meter and not capacitance. Also, SMPS operate at frequencies of 70-120 kHz, hence the ESR check frequency used by the MESR-100.


Other tools

Other options to consider include:

  • ESR-70 at around $90
    • No input protection
  • Agilent U1733C
  • The excellent Mastech MS5308, $200+, is a LCR meter. It has charged capacitor protection, the MESR-100 and ESR-100 do not.
  • DE-5000 is another proper LCR meter, manual: DE_5000_imThere is an IET DE-6000 (superceded by IET 1920) too, but I’m not sure what the differences are.
  • Uni-T UT612: Review and tear-down of UNI-T UT612 LCR meterCyrustek LCR bridge ES51919/ES51920 chipset
    • No input protection
    • The position of the banana sockets doesn’t allow a banana bridge
  • IET 5000
    • Cyrustek LCR bridge ES51919/ES51920 chipset
    • No input protection
    • Around the same price as the Uni-T (~4000 B$), but better design
    • Later designs have reverse polarity protection
  • CEM DT-9935
    • Cyrustek LCR bridge ES51919/ES51920 chipset
    • 30 V input protection
  • Extech 380193 (superceded by LCR200) – limited frequency range, no 10/100 kHz (only 120 Hz or 1 KHz)
  • BK Precision BK879B, as used in the Xerox Alto restoration, see Xerox Alto Restoration Part 1 – power supply restoration, disk drive surprise

These do not measure ESR (source):

  • AVO Megger B131,
  • Wayne Kerr 4210 and
  • Uni-Trend UT-203

Beware of version 1

Avoid the black V1 of the MESR-100: as shown here MESR-100 + JY6013 Capacitor Capacitance Cap ESR Meter Tester Combo DMM MESR-100 + JY6013 /free shipping

Why avoid this version? I can’t remember the link, probably eevblog, and the V1 had some issues. Note that the v2 comes in yellow or black, it is the shape that matters.


From DER EE DE-5000 vs MESR-100 Accuracy, an explanation of why the 100 kHz testing frequency of the MESR-100 is not ideal:

Capacitance is usually measured at 120Hz, with a 20% tolerance.
Tan d (or D on your LCR meter) is a better indication of the health of that capacitor.

So you measured 141.5uF, which is well within the 20% tolerance of a 150uF cap.
An ESR of 0.34 Ohm is probably correct, as it is close to the published max value of 0.5 Ohm.
You should also get a D (dissipation factor) of less than 0.22 for that same cap, at 120Hz.


It’s very easy to check how accurate the ESR measurement is. Take a cap, measure the ESR, then put a resistor (preferably metal film), put it in series with the capacitor, measure again. The second measurement should be equal to the first + the resistance of the resistor.

I’m going out on a limb here, but seeing as the DE-5000 is actually a proper instrument, and the MESR-100 looks like it’s been slapped together in a Chinese basement, I’d say the DE-5000 is the one that gives accurate readings here.

The DE-5000’s accuracy is given in the manual for all the ranges. What’s the accuracy spec for the MESR-100? Oh, that’s right, there is none. It’s essentially just a random number generator.

The DE-5000 has several frequency/capacitance ranges, like every other LCR meter. You can’t measure large capacitances at high frequencies, because the impedance of the DUT would be too low and thus the resulting voltage would be too low to measure. And it would be pointless, as well. That’s why capacitor datasheets specify the capacitance at 120 Hz for electrolytics or 1kHz for ceramics or film caps.

Yes, the capacitance changes with frequency depending on the type of cap. Electrolytics are extremely non linear. Try a a decent film cap, and you’ll see that the capacitance will measure essentially the same from 100 Hz – 100 kHz.

An electrolytic cap that has 2200uF printed on it really means “this cap has 2200uF at 120Hz“. At any other frequency the capacitance will be different.

In any case, measuring capacitance of electrolytics is a pointless exercise, because, they’re usually specced at -20+80%. What does measuring the capacitance tell you?

You can still measure the ESR of any DUT with the DE-5000. Simply switch to Rs mode. That will measure the real part of the impedance, i.e., ESR.

As Wytnucls already explained, measuring ESR to check if a cap is good or not isn’t very helpful. Measuring DF (dissipation factor) is much more informative. Measuring ESR can be useful when you’re comparing different types of caps for a certain application. Measuring ESR is a crutch, it’s just better than nothing if you don’t have a proper LCR meter.

So, the DE-5000 works fine and is very accurate. You just need to understand AC circuit theory better.


To measure a cap ESR, you can also do this with a function generator and an RMS multi-meter. Connect on leg of the cap to the output of the function gen (in 50 ohms output mode), the other leg to ground. Use a sine signal no higher then 100mv or so (at the frequency you want to test at), and connect the multimeter parallel to the cap to measure the voltage. We now have a 50 ohms resistor (output function gen) in series with the ESR of the cap => voltage divider network. As you know the voltage across the cap (Vcap) and the voltage of the source (Vs), the ERS can be calculated as follows:

ESR = (Vcap * 50) / (Vs – Vcap)


  • The MESR-100 is a cheap and useful device to have if budget is limited and you really do need to check ESR values
  • The DE-5000 is an excellent device for the additional cost, although with the case and all accessories, it can get up to ~£200
  • The UT612 seems to have a few failings and as it costs more than the DE-5000, it is not really worth it


Kelvin lead modification

Kelvin Resistance Probe Diagram

IMPORTANT NOTE: However, it should be noted that while these cheap Chinese (so called) “Kelvin clips” used in this video appear to be no different from those small crocodile clips that were replaced – where the sense is still terminated at the base of the crocodile clip on the same side as the test lead, rather than having the sense going to the other side – this is not the case. In fact both of the wires go to one side, but one is longer than the other and curves around to the other side, inside the croc clip handle:

Good (i.e. better) quality Kelvin leads and clips should look like these (note both the quality of the clip and the wires going to both side of the clip, not just one side – however, these are not shielded). From High Quality 4 Wires Type Microresistivity Test Lead Cable With 2 Kelvin Clip which are quite reasonable priced at £20-24:

The clips alone, are £47.83 from this supplier (there must be cheaper available), LAN]The new Taiwan ” Instek ” LCR Kelvin test clip , Bridge test clip–5PCS/LOT


Diode replacement

  • 0x000A – DE-5000 ESR Meter Diode Replacement, the early models do not have a reverse protection diode (source EEVBlog? I might have been confusing it with the Mastech AC supply issue, replies #8 and #9 – Re: Suggestions for ESR and LCR Meters). However, the later models that do have a reverse polarity diode, use a diode that blows and shorts when a reversed polarity battery is inserted, and then needs to be removed and replaced.

Other mods

ESR tables

From MESR-100 ESR Meter Review and Teardown

ESR table - MESR-100 ESR table – MESR-100

From this post on My latest bit of gear has arrived

From this post on the same thread

From ESR meter table

From electrolytic capacitor esr chart, which has a number of ESR tables, a poor quality gallery:

end of gallery

Cheapest sources


The DE-5000 has a strange (cunning?) price structure – the base unit is relatively cheap, but all of the accessories together cost more than the base unit (with the PSU and the USB option being the most expensive, and the guard cable is especially well over-priced), thereby doubling the price, and then there is the additional cost of the hard case to put it all in..!

The whole lot (including case) would set you back ~$195 (£150), but you could get the bare minimum set (meter plus probes) for ~$101-105 (£77-79), or the complete set (without the case) for $160 (£125). It really is the combined cost of the USB and the PSU that, IMHO needlessly (after all, how often are you going to use them (although as noted below, the PSU saves the calibration)?), bumps up the cost by another $60.

Individual parts

  • TL-21 $18 (£13)
  • TL-22 $19 (£15)
  • TL-23 $20 (£15)
  • PSU $26 (£20) – Useful, to prevent Auto Power Off (APO) as APO causes the calibration to be lost, and re-calibration is again required. Note that even unplugging the PSU ca cause the calibration to be lost. (Source at 17:43).
  • USB $70 (£53)
  • DE-5000 $80 (£60)
  • Case $34 (£25) – DE-5000-CS



There are multiple combinations of deals, each differing in cost (~$195), but all cheaper than the complete set ($210) by a saving of $15

Meter and three accessories + case = $104.50 + $33.77 = $138.27, while the cheapest, does not offer a cheap upgrade to completing the accessories (with the USB and PSU)

Meter and case + all accessories = $104.99 + $91.89 = $196.88

Meter and all accessories + case = $162.69 + $33.77 = $196.46


MESR-100 ESR Capacitance Ohm Meter Cap Resistance Capacitor In Circuit Tester, US $21.00 Approximately £16.15 (half usual price, looks like a scam). I purchased this, let’s wait and see what happens. I got an “item posted” notification, but that was about as far as it went… despite all of the tracking, and it stating that the item was delivered, I never actually received it:

However, I did get an immediate refund when I raised the issue with the seller.

Other example prices: MESR-100 Capacitor Ohm Meter Repair Capacitance Resistance Circuit Tester, £32.38+£3.50, £29.00 + £3.95



Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s