Is the ability to measure the phase angle useful in LCR Meter? - Page 1
Forum section: electronics / testgear

author: fishandchips
author_rank: Regular Contributor
timestamp: April 17, 2017, 01:16:55 am
content: Due to the difficulty in finding an easy and accurate way to measure the inductance of a DC motor, I am considering to buy a LCR meter. I am considering the DE-5000, Signstek M4070 and the Aide Tek DM4070. I read that the DE-5000 could "measure Inductance/ Capacitance/ Resistance with secondary parameters including dissipation factor (D), quality factor (Q), phase angle , equivalent series/ parallel resistance (ESR or Rp)." Is the ability to measure phase angle useful?I guess the Signstek M4070 may be better than the Aide Tek DM4070 as the former can measure a larger inductance range. The DE-5000 is probably the best but cost about two times more.By the way, what is the difference between SODIAL (R) M4070, Signstek M4070, Hwydo M4070? It seems that just like the DE-5000, some may not include the probes nor usb cable.

author: mos6502
author_rank: Frequent Contributor
timestamp: April 17, 2017, 05:46:05 am
content: Well, of the meters you mentioned, only the DE-5000 is an actual LCR meter. Being able to measure phase angle is a prerequisite of an LCR meter. All the other values are derived from phase angle and voltage. So you usually get the option of displaying it, even if it's rarely useful.There are meters that claim to be LCR meters (like the two you mentioned), but what they usually do is have an LC oscillator and put the DUT in parallel of the L or the C and measure how the frequency changes. This is of course totally freaking useless, since that way you can't determine the most important parameters like DF and Q, and the measurement frequency will be who-knows-freaking-what (dependent on the DUT) and not selectable.

author: fishandchips
author_rank: Regular Contributor
timestamp: April 17, 2017, 01:13:02 pm
content: From user reviews in Amazon, users mentioned that the measurements of those two meters are accurate. So, they may think that the values are correct but they are not quite correct? I have been asking around but there is no step by step procedure to measure the inductance. To model the motor in computer simulations, is it worth to invest on the DE-5000? Can't think of other use of lcr meter except for this one time use. I already got two multimeters.

author: HighVoltage
author_rank: Super Contributor
timestamp: April 17, 2017, 01:35:30 pm
content: You sometimes can find a professional LCR meter on ebay cheap, like theFLUKE PM6306It measures phase angle of course and much more

author: fishandchips
author_rank: Regular Contributor
timestamp: April 17, 2017, 02:02:39 pm
content: So it is better to spend some money to get a meter than trying to measure it indirectly using a function generator?

author: RandallMcRee
author_rank: Frequent Contributor
timestamp: April 17, 2017, 04:46:10 pm
content: Before you spend hundreds of dollars (up to $1000s) on a new meter, perhaps you could tell everyone what you are trying to accomplish by measuring the motor? What's your end goal?There are two possibilities, I see here;1) The lcr meter will measure inductance, yes, but not at the frequency you need for your end goal;2) Inductance is actually NOT the important parameter (or just one of many) in YOUR application and so an lcr meter is not the answer.

author: edavid
author_rank: Super Contributor
timestamp: April 17, 2017, 06:12:58 pm
content: Quote from: mos6502 on April 17, 2017, 05:46:05 amI think it's too strong to say they are useless. For the case of measuring the inductance of a DC motor, the L will be high and the R will be low, so the simple LC meter will be able to do a good job. I can't see that the true LCR meter will lead to any improvement in the quality of a simple motor model.

author: TurboTom
author_rank: Super Contributor
timestamp: April 17, 2017, 08:14:29 pm
content: And don't forget: If your motor is euqipped with permanent magnets,neverrotate the shaft while your LCR meter is connected to it. The EMF can easily damage its inputs.Cheers,Tom

author: Kleinstein
author_rank: Super Contributor
timestamp: April 17, 2017, 08:26:32 pm
content: For Testing something like a motor it might be better to use a function generator and scope instead of a cheap LCR meter. Of cause this will be slow compared to using a direct reading meter, but you can choose the frequency and accuracy is not that important.The motor, like other parts with a laminated iron core behave different at different frequencies. So even the simple LR series model is that accurate. So it would make a difference at which frequency you measure.The very cheap meters use a variable frequency, depending an the sample. If you are lucky they tell you the the frequency, but chances are it is not in the right range. So it might help, or not. The better LCR meters use a fixed frequency and some even allow to chose a suitable frequency.

author: mos6502
author_rank: Frequent Contributor
timestamp: April 17, 2017, 08:32:38 pm
content: Quote from: edavid on April 17, 2017, 06:12:58 pmThe problem is that with most reactive components, the impedance is highly dependent on frequency. Your oscillator-type LCR "meter" will 99.9% of the time oscillate at a different frequency than what component is used at. So you hook up your motor and the "meter" shows some inductance value at, say, 332.4Hz. That's entirely useless, because the motor's inductance will be completely different at 50 or 60 Hz. That's the reason why real LCR meters offer so many different frequencies.Quote from: TurboTom on April 17, 2017, 08:14:29 pmExcellent point.

author: edavid
author_rank: Super Contributor
timestamp: April 17, 2017, 09:21:47 pm
content: Quote from: mos6502 on April 17, 2017, 08:32:38 pmOP wants to measure the inductance of aDCmotor. Why would the inductance of a DC motor have a strong frequency dependence?(And if it did, wouldn't that also make a DE-5000 useless for determining model parameters?)

author: Kleinstein
author_rank: Super Contributor
timestamp: April 17, 2017, 09:48:42 pm
content: For an inductor with a core made of relatively thick iron layers, there will be eddy currents if the frequencies are high. So the inductance will be high at low frequencies and starting somewhere in the kHz range the inductance will be going down and can be much lower in the 100 kHz range.With the usually relatively large inductance of a motor, chances are not that bad, that the cheap meters will end up at a relatively low frequency.If the DE-5000 is much better depends on the frequency used. At least chances are you get that from the manual upfront. Also something like 1 -10 kHz is a likely range.For using / modeling a motor one would likely need the inductance for the 50 Hz to low kHz range, depending on the speed and use. So anything up to about 10 kHz test frequency should be acceptable.

author: MrW0lf
author_rank: Frequent Contributor
timestamp: April 18, 2017, 09:06:57 am
content: With good LCR meter you can take 0.1kHz, 1kHz, 10kHz, 100kHz point params and make quite accurate model in simulator that matches points or just calculate single point of interest by hand. I've used this very successfully with building completely custom motors.

author: edavid
author_rank: Super Contributor
timestamp: April 18, 2017, 03:16:36 pm
content: Quote from: MrW0lf on April 18, 2017, 09:06:57 amCan you post the data for one of your motors?

author: TimFox
author_rank: Super Contributor
timestamp: April 18, 2017, 09:36:29 pm
content: One reason to use the phase angle measurement on a DE-5000 is to avoid ambiguity between inductive and capacitive impedances: the DE-5000 always reports a positive value for the value ofLorC, whichever was selected by the user in manual mode. The phase angle will read out as positive or negative. For example, when measuring the (relatively low) series inductance of a wire-wound power resistor the net impedance may be capacitive at high frequencies (due to the parasitic capacitance of the package and between windings), which will appear as a strange inductance value ifLseriesis selected for the measurement.

author: fishandchips
author_rank: Regular Contributor
timestamp: April 18, 2017, 10:00:32 pm
content: Quote from: edavid on April 18, 2017, 03:16:36 pmWhat parameters do you need?

author: fishandchips
author_rank: Regular Contributor
timestamp: April 18, 2017, 10:03:07 pm
content: Quote from: RandallMcRee on April 17, 2017, 04:46:10 pmI try to simulate the motor in computer simulations so that the motor behaves like the real one.

author: fishandchips
author_rank: Regular Contributor
timestamp: April 18, 2017, 10:05:49 pm
content: Quote from: Kleinstein on April 17, 2017, 08:26:32 pmSo, the DE-5000 is better than the other two I mentioned?

author: fishandchips
author_rank: Regular Contributor
timestamp: April 18, 2017, 10:08:16 pm
content: Quote from: mos6502 on April 17, 2017, 08:32:38 pmIs the DE-5000 a real LCR meter by your definition? From another post, it seems that it is.

author: MrW0lf
author_rank: Frequent Contributor
timestamp: April 19, 2017, 08:50:49 am
content: Quote from: edavid on April 18, 2017, 03:16:36 pmMy electronics hobby started with building pulse motors. Was not pleased with common circuits/performance circulating on the net. So tried to improve thing or two - mainly get rid of losses, manage flyback better etc. Most critical part was making low-loss coils. 0.1...100kHz LCR meter quite ok for that (used Agilent U1733C). This was several years ago do not even have complete motor at hand right now, only 1 picture (attached). As you can see highly experimentalHowever thinking rebuilding in more polished style and possibly putting on tube.

author: fishandchips
author_rank: Regular Contributor
timestamp: April 19, 2017, 11:10:30 am
content: How useful it is to be able to save the inductance vs. time data to a PC? What about optical coupling. Trying to decide whether to buy the full set or just the Basic cable set.

author: MrW0lf
author_rank: Frequent Contributor
timestamp: April 19, 2017, 11:30:48 am
content: Quote from: fishandchips on April 19, 2017, 11:10:30 amPC link is useful for testing large batch of similar components for small production run etc. Perhaps monitoring some physical process (LCR changes vs temperature etc). With motor it might be useful to log inductance vs rotor position. But same could be done with 10 datapoints by hand soMine has IR-to-USB but never bothered...

author: fishandchips
author_rank: Regular Contributor
timestamp: April 19, 2017, 12:46:03 pm
content: Quote from: MrW0lf on April 19, 2017, 11:30:48 amIt seems that some companies sell only the meter; meter + TL-21 and TL-22; meter + TL-21,22 and 23; or the full set. Some companies seem to put TI instead of TL. Not sure if it is a typo.I don't think I will use the TL-22 SMD but the price difference is negligible. Now, try to decide if I should get the meter with TL-21 and TL-22 or the full set. Price difference is about US$80.Do you mean the Optical IR to USB PC link (USB/CD can send to the PC via USB measurement data.) and CD are useful? Can it log inductance vs rotor position over time? Am I right that for sure, it can log inductance vs. time data?