ESR meter questions - Page 1
Forum section: electronics / beginners

author: JHAnd
author_rank: Contributor
timestamp: October 03, 2023, 07:39:40 pm
content: Hi!I'm learning how to use an ESR meter and need help with interpreting the results when measuring capacitors and transistors.First of all, this is a Chinese cheap meter bought on amazon... a "BSIDE ESR02 Pro"CapacitorI have tried testing the same 1uF/35V capacitor both in and out of circuit with the ESR meter.In circuit:Capacitance = 2.598uFVloss = 3.1%ESR = 3.2 OhmsOut of circuit:Capacitance = 0.955uFVloss = 0.1%ESR = 2.9 OhmsSchematic:Cap #7 in below schematic is the one tested.https://imgur.com/a/DI7VNAGHow should I interpret these results, and what values should I ignore?Should I ignore the capacitance result from the in circuit test and only look at the ESR?The ESR value seems to be about the same both in and out of circuit.What about V-loss? Can I look at V-loss in circuit or is it only valid when testing out of circuit?Here the results are quite far apart with a x30 increase in VLoss when measuring in circuit.The back of the ESR-meter has a table and it says "1uF/35V cap - 9 Ohms". Does that mean that as long as the cap reads 9 ohms or under, it is a good cap? Is this true both in and out of circuit?TransistorResults from the transistor measurement:https://imgur.com/a/3k9St4jThe transistor is detected as a N-JFETPins functions are detected: (see picture)I = 0.71mA@Vg=0.49VI'm not sure what the numbers mean?I only tested the transistor out of circuit, I'm not sure if I can test a transistor in circuit with the ESR meter...can I?

author: Vovk_Z
author_rank: Super Contributor
timestamp: October 03, 2023, 09:37:53 pm
content: As for capacitor measurements: this meter is typical simple RLC and transistor multy-tester. It doesn't have in-circuit measurents feature so it is intended to use only off-circuit.As for what to look at: you may look at datasheets of parts under test. You may compare only parameters stated by manufacturer. That's capacitance for capacitors and ESR for low-ESR capacitor types. If you test not low-ESR capacitor (e.g. general use or high-temperature type) you may check its ESR too - it is typically 2-4 times larger then similar low-ESR.You may use Vloss parameter too but it is used by multy-tester manufactufers only and it is not used by capacitor manufacturers typically so you have to gather your own database for it. Typically low Vloss is ok (IDK, < 5%) and high Vloss is not ok (>10..20% possibly). I use professional RLC-meter which doesn't have this parameter so IDK about it much.

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: October 04, 2023, 06:23:45 am
content: If you check the user manual for a Peak Instruments ESR meter, it gives typical values for a range of capacitors:https://www.peakelec.co.uk/downloads/esr70-user-guide-en.pdfSJ

author: strawberry
author_rank: Super Contributor
timestamp: October 04, 2023, 12:39:00 pm
content: Incircuit measurement is done at low voltage levels. That multi tester use ~5V pulsed source . When some Vbe(0.65V) is clamping and code is not enough advanced to detect it (continous sampling? could help)

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: October 04, 2023, 12:53:27 pm
content: These inexpensive BSIDE component testers are amazing.I have one and it is accurate enough for my hobby needs. It is invaluable for testing transistors. The Resistance and capacitance measurements are quite good also.The usefulness of even the meters designed for in circuit testing is very limited, this one is not for in circuit testing as you have discovered. Any meter will only measure the value that is obtained in the circuit with every other component attached and affecting the reading.The in circuit testers that I am familiar with just use a very low voltage that is lower than a typical PN junction voltage to try to eliminate the effects of transistors on the reading. This is sometimes helpful but not a tremendous advantage.Most inexpensive testers will not test at low values of cap and inductance. The BSIDE will not either.

author: u666sa
author_rank: Frequent Contributor
timestamp: October 04, 2023, 11:05:00 pm
content: Quote from: JHAnd on October 03, 2023, 07:39:40 pmThis is what I usually do, I go to google images and search for "esr table". For your example, 1uF 35V should have 2.4 ESR, and the lower it is the better. Then I take cap out of circuit, always, I don't bother with in circuit testing.And test the cap. Your result is 2.9, which is on the high side.Before I bought my hantek 1833C, I went up and down caps on one of my broken tv's. Voltages were okay on rails, flash ic was swapped from working tv. It had stand by light but would not turn on. PERIOD. I tested caps using your regular capacitance tester, all checked out good. Then ESR meter arrived, and I went over caps one more time, out of circuit. One cap near CPU had higher than spec ESR. I replaced it, and tv turned on. So high ESR caps can indeed be the cause of the problem. How high is okay or not okay I do not know. But with your cap measuring at 2.9 I would replace it.Now... Lately, new caps I buy from the store have higher ESR than the bad caps I'm replacing. So you have to watch out for what you buy. Always test new caps you bought, they can be bad.

author: Veteran68
author_rank: Frequent Contributor
timestamp: October 05, 2023, 03:55:38 pm
content: Quote from: u666sa on October 04, 2023, 11:05:00 pmThere is more to it than that. Yes, this can give you rough idea for your general run of the mill electrolytic found in most SMPS, but doesn't take into account the following:"Good" ESR depends on the capacitor type and construction. There are "low" ESR caps and "regular" ESR caps. Without knowing what you're testing, it's hard to say what's "good vs bad" with any degree of confidence, unless it's just off the charts for any type of cap.Acceptable ESR also depends on the intended use caseAgain depending on construction, capacitance levels, and use case, ESR should be measured at a particular frequency or frequencies. The ESR specified in datasheets will usually specify the frequency. The cheapest ESR meters use a fixed frequency, maybe 100-120Hz or 1Khz, which may fit a sweet spot of common caps and values, but will not be accurate for other types of caps. Higher end LCR meters allow for selecting the test frequency across a broad range, say 100Hz-100Khz. Generally speaking, higher capacitance values should be tested at lower frequencies, and lower capacitor values at higher frequencies.In all but extreme cases of obviously high ESR, it's more about using your knowledge of the circuit in question combined with your discernment of multiple criteria beyond just a simple ESR table of static values. Then again with something like typical SMPS electrolytics, if any reading is even remotely questionable, it's cheap enough to just replace it rather than spend a lot of time validating your readings with more expensive test equipment.

author: KungFuJosh
author_rank: Super Contributor
timestamp: October 06, 2023, 01:59:08 am
content: Quote from: JHAnd on October 03, 2023, 07:39:40 pmI don't usually test in circuit. The main reason being is that the circuit will almost always influence your results. The difference in capacitance you measured? Parallel capacitance in circuit changed your results.More importantly, always be safe and discharge caps before measuring.