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| ET432 LCR Meter - Wild Results - Range Function? |
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| killingtime:
Hello, I was attempting to take some transformer winding resistance readings with an East Tester ET432 LCR meter this evening, and was getting some very odd results. This meter has a DCR function meaning no AC is used. This is necessary when measuring the winding resistance of an inductor as the reactance alters the measurement. There's no series or parallel equivalent circuit in this mode, and no frequency setting. The only parameter you can alter is the RANGE, which cycles through 100Ω, 1KΩ, 10KΩ, 100KΩ and AUTO. AUTO normally gets it right, but on some occasions it gets it wrong and you have to manually pick a setting. So far so good. It can't be that different to a multi-meter right? A DMM has different resistance ranges. You pick the one that gives the most precise reading. 3.001 KΩ and not 0.003 MΩ. Should be easy. Cycling through the range options gives wildly different results. For a 10KΩ 5% resistor in DCR mode after performing an open & short user calibration (2 wire): 100Ω - 921.6 KΩ 1KΩ - 98.92 KΩ 10KΩ - 9.953 KΩ 100KΩ - -9.259 MΩ (minus!) AUTO - 9.953 KΩ I'd expect some loss of precision as you move around the ranges, but the above are at least an order of magnitude out. There's no warning it's out by such a margin either. You just have to know. To confuse matters a bit more, the manual lists a bunch of 'ranges' for the DCR mode that are not available on the unit. Extract from the manual attached. Manual lists 0.4Ω, 40Ω, 400Ω, 4KΩ, 40KΩ, 400KΩ, 4MΩ, 10MΩ and 20MΩ. So either: 1) The ranges in the manual never made it into the production model or, 2) They've just copied stuff from another manual (Keysight) or, 2) I've misunderstood how ranging works on an LCR meter. Meter has the same issues on L or C ranges as well. Exact same options for RANGE. Changing measurement speed to slow doesn't improve matters either. Using 4 wire kelvin probes has little effect. Do any of the Keysight_U1731C / U1732C / U1733C work the same way, or have the same issues? I wouldn't expect the values to be this far out. If anyone has a U17xxx Keysight LCR I'd be interested to know what you see when manually ranging. Thanks. |
| csuhi17:
If I understand the description correctly. there is a physical range which is 100, 1k, 20k, 100k. It has to do with the resistors in it. And there is what you shared from the description, the value that can be read from the display. for example, if you start adjusting a 0-220 ohm pot, you will see a change in resolution at 40 ohms. From 39.999 ohms to 40.00 ohms. The accuracy associated with these has been described. |
| killingtime:
>>The accuracy associated with these has been described. It has been described in the manual, but it's not meeting those accuracy specs at all, apart from on one range, and you have to guess the range correctly, which makes the whole exercise a bit pointless. The whole point of a measuring device is to take the guess work out of it. To be clear, a 10K resistor displays as 921.6K on the 100 Ohm range, and 98.92K on the 1K range, which isn't 0.x% + x digits is it? That's out by a factor of 9116% on the 100 Ohm range. That and the fact there isn't a 100 Ohm range in the manual, only 40 Ohms and 400 Ohms... I wonder if the guy that wrote the manual actually had this unit in his hands to test with, or perhaps he just borrowed something else. Edit: Manual is here in case anyone else has this meter. https://www.easttester-cn.com/uploads/ET430-HANDHELD-NEW-COMPACT-LCR-METER-USER-MANUAL.pdf |
| Tycho_Brahe:
I have a slightly different model (ET431). So, I used a 10K carbon film resistor 5%. This thing has kelvin clips, so I just used those right off the bat. I 'think' I got results similar to you. Used DCR mode and got: RangeOhms Measured100908 K1 K98 K10 K9.848 K100 Knegative 2.1 MAuto9.849 K I guess I never noticed this before because I just rely on Auto. Thank goodness Auto usually picks the magic range. But what the heck? I'm also wondering if I'm just using the thing incorrectly (I wouldn't be surprised as I really don't know my around this device yet). So you say it also happens when measuring capacitors and inductors (I didn't have time to test that tonight)? Hey, so when you said on rare occasions the Auto setting gets it wrong and you have to resort to a manual range, how wrong was Auto? Was it as crazy wrong as some of our numbers (like orders of magnitude and sometimes even crazy negative values)? |
| killingtime:
--- Quote from: Tycho_Brahe on January 23, 2024, 04:59:20 am ---... how wrong was Auto? --- End quote --- From the testing I've done, it depends on where the value you're measuring is compared to the nearest range. After the 10K I tried a 5.6K as it's half way between the 1K and 10K ranges. I got 5.6K and 7K on different ranges. The other values were out by a factor of at least 10. If your DUT is near a range, one range reading will be accurate, and all the others will be out by a factor of 10 at least.... which is fine if you already know the value of your DUT, but if you don't then it's all guesswork. I'm thinking of smd capacitors and toroidal core inductors, both of which are usually unmarked. In my case I was measuring the primary inductance of a 3KVA line transformer with the output unloaded (so just a large inductor). AUTO was giving me 0.7H which I thought was low, as transformers like this normally measure above 8 Henries (depends on the core type, number of windings and other things). The next range gave me the correct reading (9.9H). If you're getting similar readings to me, then I didn't get the 'Friday afternoon model' and this is either just the way this meter has been designed, or it's how all LCR meters work. If anyone has a different brand LCR hand held (Keysight or BK Precision) I'd be grateful if you would stick a 10K metal film on it and play with the range setting. That will tell us if it's worth spending about 3x for a different design. Many thanks. |
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