LCR meters are a handy tool to have in your kit, especially now that surface mount devices are the norm in designs.
I’ve always found LCR meters to be a handy tool in my kit, especially now that surface mount (SM) devices are the norm in designs. I don’t know about you, but there are times when I end up with a dozen SM devices on the desk and an LCR meter is invaluable for identifying resistors from capacitors from inductors!
A few years ago, I reviewed the Advanced Devices model ST5 “Smart Tweezers” LCR meter made expressly for measuring SM components. I also compared it to a similar product selling for about $30 (Reference 1).
I really liked the latest Smart Tweezer ST5, because it was small and easily fit into my EMC troubleshooting kit. However, the biggest issue was the short battery life and the fact that the “dark” current (current when the unit was turned “off”) tended to run the battery down. Every time I reached for it, the battery was dead and had to be recharged. The cheapo “LCR” meter tweezers, model VC6015, while accurate, lacked measurement capability for inductors, so wasn’t that useful, either. There are similar LCR meters to the ST5 advertised currently at Seeed Studio and on eBay, but they have a lot of negative comments about “wonkiness” and instability of the user interface.
Walfront/Mastech MS5308 LCR meter
So, in my continuing search for the ultimate LCR meter, I ordered the Walfront/Mastech MS5308 ($254.69) after reading some good reviews on Amazon. The meter came with two accessories I deemed imperative: a Kelvin probe for measuring leaded components and a surface mount tweezer probe. The probes plug into the front measurement slots. If the leads are long enough, leaded components can be measured by pushing them directly into the slots.
I tried measuring a few leaded and SM components at five different frequencies and found the meter to be unstable at some frequencies. Some components never settled to a steady value, with some measuring way off. Interestingly, about half the measured components were right on (as compared with the ST5 Smart Tweezers). The Kelvin probes seemed to be the worst as far as stability. In addition, the unit required eight (!) AA cells to power it. After loading fresh batteries, I still got only four out of five bars on the battery meter. I returned it.
DER EE DE-5000 LCR meter
This instrument looks very similar to the competing B&K Precision and Keysight meters. It also got rave reviews (not that I completely trust Amazon reviewers) and may be ordered with or without the Kelvin and SM tweezer probes. I ended up getting the full kit, which came in a nice plastic case with molded inserts. Besides the probes, included were a wall-wart power supply, ground wire with banana plug, an optical interface, 9V battery, and remote software ($179.99).
I’m happy to report this meter seems very stable with relatively good quality construction. The Kelvin probes are a little short for my taste, but the tweezer probe seems pretty nice; although, it could use some serrations at the tips of the tweezers to better hold components. Also, when the rear stand is deployed, the lack of rubber feet on the bottom allows the instrument to slide around on the desktop. Like the Mastech, the probe contacts slide into the front slots.
The DE-5000 includes an “open – short” calibration feature, where the calibration is performed with open probe connections, then shorted probe connections. The calibration cycle is 30 seconds per measurement, which I feel is a bit too long. Calibrating the meter helps “zero” out the 0.2 pF (typ.) parasitic capacitance (for example) of the tweezer probe.
Measurement results and comparison
I tested both meters with a variety of components I’ve been using as standards through the years. Both meters include test frequencies of 100 Hz, 120 Hz, 1 kHz, 10 kHz, and 100 kHz. They both provide secondary measurements of D, Q, ESR, and phase. Both can be configured for “pass/fail,” if sorting a bunch of identical component values.
I tested each component at several frequencies. For some components, the Mastech meter seemed unable to settle on a measurement at certain frequencies or gave me an answer way off from the others. The DER EE meter was stable at all frequencies and component types.
Typically, you’d expect a measured capacitor to gradually measure decreases in capacitance as the frequency increased. For example, a 470pF CK05 may measure: 474, 469, 462, and 451 pF as the frequency was stepped 100Hz, 1kHz, 10kHz, and 100kHz, respectively. This is entirely normal and is due to the frequency response of the dielectric material. Another example would be increasing Q with frequency for inductors (decreasing Q for capacitors).
Figure 4 shows the results of the past and current measurements. I’ve included past measurements taken using the HP4262A LCR meter, as well as the ST5 Smart Tweezers and the inexpensive VC6015 tweezers (Reference 1). As I mentioned, the VC6015 cannot measure inductance and is so indicated in the chart. The Mastech MS5308 had several bad measurements and had issues with unstable measurements.
Figure 4 The DE-5000 meter did very well during the comparison with the HP4262A and ST5 Smart Tweezers.
While there are many more LCR meters available, the DER EE model DE-5000 meter and accessories was impressive and came at an affordable cost, so I would recommend it. The Mastech model MS5308 had consistent trouble making some measurements and so is not recommended.
This article was originally published on EDN.
—Kenneth Wyatt is president and principal consultant of Wyatt Technical Services.