Why handheld DMM and LCR do not combine? - Page 1
Forum section: electronics / testgear

author: omgfire
author_rank: Regular Contributor
timestamp: July 08, 2014, 11:19:12 am
content: Hello,I am not sure about right subforum to ask this question, so sorry for inconvenience.I ordered DE5000 LCR meter from japan ebay seller. That made me thinking why do I need two dedicated devices for DMM and LCR measurement. I have looked attear downof DE5000, and, besides Cyrustek ES51919/ES51920 IC, LCR meter DE5000 consists of air and things that DMM has (battery, case, display). Price for DE5000 is 4700 Yen in Japan (google estimates it as 46 USD), which is lower than a decent DMM.There is continuous feature war between DMMs: diode test, frequency, duty cycle, capacitance, temperature, LoZ, etc.But, why can't I see any DMM with Cyrustek's LCR capabilities (ESR, 4wire, Q, etc.)?

author: Fsck
author_rank: Super Contributor
timestamp: July 08, 2014, 12:02:42 pm
content: space is a bit of an issue for full fledged DMMs. HRC fuses + HV isolation take up a big chunk of space. since an LCR meter wants 4 terminal measurements + possible guard, I don't see where you're going to put those on say a Fluke 87.add to the fact that DMMs are electrical-oriented, and you're not likely to find that many buyers for your DMM+LCR combo. (it'll also have to be like Fluke 289 size)it's possible that you could do a meter with like cat2 1kV rating and add that LCR combo in for electronics but it'd probably end up as a jack of all trades, master of none. could be a crowd-funding idea!

author: Psi
author_rank: Super Contributor
timestamp: July 08, 2014, 12:27:55 pm
content: Some DMMs do measure inductance, capacitance and of course resistance.Id be more interested in seeing ESR measurement built into a meter to be honest.Checking for bad caps has become something needed just as often as measuring capacitance

author: PedroDaGr8
author_rank: Super Contributor
timestamp: July 08, 2014, 02:13:56 pm
content: Quote from: Psi on July 08, 2014, 12:27:55 pmBut they don't do it nearly as well as a true LCR meter does.Also, you have to remember most LCR's have no input protection. That is for a reason, things like fuses, spark gaps, PTC, MOVs etc. all add capacitance and/or inductance to the input. While it might be possible to zero some of it out, if any of these are sensitve to temp or self-heating that would be virtually impossible to do.

author: jmoreland79
author_rank: Regular Contributor
timestamp: July 08, 2014, 04:36:40 pm
content: Quote from: PedroDaGr8 on July 08, 2014, 02:13:56 pmThat's the reason there. While an LCR meter and a DMM are about the same size and have a set of inputs, the circuit design in each is very different. It would be extremely difficult to design a DMM capable of measuring high voltages and currents while maintaining the isolation needed to measure the precise values that an LCR can. For example, my Fluke 189 will only measure capacitance down to 1 nF, while my BK 879B will read down to 40 pF. I only trust the 189 for capacitance measurement if it's a really large value, or if I just need a ballpark idea of a smaller component because it just isn't that accurate.And it isn't just the added protection components in a DMM that you mentioned, but the layout of the traces and components on the PCB itself that limits them for frequency dependent measurements.