Brymen 869 resistance measurements and equipment recommendations  - Page 1
Forum section: electronics / testgear

author: dolivas27
author_rank: Contributor
timestamp: February 11, 2018, 02:39:29 pm
content: Hi Guy’s and Gal’sI am new here well I have not been on in sometime and for some reason my account was gone so recreated it with the same user name.Ok on to the questions I am having a problem with the Brymen BM869 reading low ohm resistors. The resistors I am testing are .22 Ohm and the Brymen just does not read them right it always reads much lower than the resistor real value?If I read the same resistor with the Keysight U1273A it reads the value of the resistor right every time.I purchased the BM869 new from TME late last year as a second bench meter and to be honest with you just don’t like somethings on this meter the one thing I hate is there is no buzzer on the diode mode make testing transistor a pain always having to look at the meter.So, is the real problem the specs on the Brymen?I am looking to replace the Brymen on the bench with a real bench meter at this point, but I am not sure what to purchase. I have been looking at the Rigol DM3058E and the Rigol DM3068I am leaning for the Rigol DM3068 just for the specs on it or should I just spend the money and get a new Keysight bench meter?Here is what I am getting ready to purchase in the next month I am just not sure on the bench meter looking for some input.Rigol DP832 (Please suggest others is there is something better in this range or a few dollars more.)Rigol DS1054Z (This will be my first scope it’s time for some of the repairs I have been doing)Tripp Lite IS1000HG Isolation Transformer (Needed for working on power supplies when using the scope)Bench Meter (Trying to figure out what to purchase)Thanks for the help,Dean

author: mimmus78
author_rank: Unknown
timestamp: February 11, 2018, 04:24:47 pm
content: Quote from: dolivas27 on February 11, 2018, 02:39:29 pmWhat reads if you short the leads?Inviato dal mio ONEPLUS A5010 utilizzando Tapatalk

author: mos6502
author_rank: Frequent Contributor
timestamp: February 11, 2018, 04:53:24 pm
content: Sell the Brymen and get a Fluke 87V. It is still the best general purpose multimeter. Diode test is one of the most used modes on a multimeter when repairing electronics and to not have the audible diode test is just inexcusable. By the way, the Fluke 87 III and the original 87 do not have the diode beep. But the original series 77 does. Go figure.

author: nctnico
author_rank: Super Contributor
timestamp: February 11, 2018, 05:58:20 pm
content: For measuring low value resistors you need a meter which uses 4-wires.I've got this cheap LCR meter from Ebay and it works well for measuring low value resistors. For the price you can't go wrong.https://www.ebay.com/itm/LCR-Auto-Digital-Electric-Bridge-Resistance-Capacitance-Detector-Inductance-0-3/182948704552Besides resistors an LCR meter can also measure inductors and capacitors (including ESR / series resistance).A cheap bench meter which isn't sexy but works very well is the VC8145. I use these as my daily driver bench DMMs because they start quick and have instant continuity. If you need more accuracy then get the Keysight bench DMM. The price difference between getting the real deal versus the ones from Rigol or Siglent isn't worth the trouble you may get.The same goes for a bench power supply. GW Instek has several relatively cheap base models which have a good price/performance ratio but personally I choose to go overboard and get the Keysight E36313A. It is accurate and has a low current measurement mode which is nice when working on battery powered project because you can measure the standby current with the PSU as well.Edit: cheap GW Instek PSU reviewhttps://www.eevblog.com/forum/testgear/gw-instek-gpe-2323-rs-pro-rpe-2323-review/For working on power supplies you need to shell out more money and forget about the isolation transformer. A differential probe is the way to go here and MicSig sells cheap ones which work well. With a normal probe you will ground the device through the oscilloscope and in case of an isolation transformer you bypass the safety provided by ground and the GFI (having an extra low current GFI to power your bench is a good idea).

author: HKJ
author_rank: Super Contributor
timestamp: February 11, 2018, 06:29:15 pm
content: Try shorting the probes and using the delta button, before measuring low ohms.The best solution if, of course, four terminal measurement usual with a bench meter.If you have a power supply with a good constant current mode, you can do your own four terminal measurements with good precision using any multimeter.

author: mos6502
author_rank: Frequent Contributor
timestamp: February 11, 2018, 06:34:25 pm
content: Quote from: nctnico on February 11, 2018, 05:58:20 pmWell ... not really. For one, you can use your bench power supply and put a constant current through the resistor. 1000mA is a good value, then you measure the voltage drop at the resistor with your multimeter and you can read the resistance directly in millivolts=milliohms. This is very accurate. Of course, this is a four-wire measurement.But even with a good multimeter that has at least 10 milliohms resolution and AutoHOLD (like the 87V, unlike the Brymen with is useless "display freeze" hold function), you can do a decent job at doing reliable low ohms measurements. Switch your 87V to high resolution and then the 600 Ohm range. Then, you activate AutoHOLD. AutoHOLD will only register a reading if the measurement has been stable for at least 300ms - this is perfect for eliminating those stray readings when your probes don't have good contact. Then, you can use both hands to make your measurement on two adjacent spots of the resistor lead, remove the probes once you have a reading and then press the rel button. This will give you a good zero. Then measure the resistance as normal using the AutoHOLD mode. This will give you reliable readings with an accuracy of +/- 20 milliohms.

author: joeqsmith
author_rank: Super Contributor
timestamp: February 11, 2018, 08:33:23 pm
content: Quote from: dolivas27 on February 11, 2018, 02:39:29 pmHard to say without seeing some data. I would have no idea what "much lower" means. With the meter only having a 0.01 ohm resolution you may be asking too much out of it. I assume you know what the actual resistance is to a degree tighter than the meter. You have the manual. Did you check it? If the meter is out of spec, maybe you could have it aligned stateside.A member here recently posted a review of a fairly inexpensive meter that could read sub ohm resistances.

author: dolivas27
author_rank: Contributor
timestamp: February 11, 2018, 11:21:07 pm
content: Quote from: nctnico on February 11, 2018, 05:58:20 pmIs this the differential probe your talking about?https://www.amazon.com/Micsig-DP10013-Differential-Attenuation-Tektronix/dp/B074K4XPW3/ref=sr_1_3?ie=UTF8&qid=1518390593&sr=8-3&keywords=micsig&dpID=51g5DxENBhL&preST=_SY300_QL70_&dpSrc=srch#customerReviewsIf so that would save me the cost if the Isolation Transformer for working on SMPSThanks for the info lots to learn I have not used a scope in years.....

author: nctnico
author_rank: Super Contributor
timestamp: February 11, 2018, 11:24:10 pm
content: Yes, that is the differential probe I'm talking about.BTW there are other techniques to diagnose switching power supplies as well. What I do in case the problem is more complicated than a blown transistor, leaky capacitor or blown diode is to power the primary and secondary control circuitry from a bench power supply. That way you can check things like gate/base drive pulses, the feedback control loop, etc without having lethal voltages present.

author: dolivas27
author_rank: Contributor
timestamp: February 11, 2018, 11:41:20 pm
content: Ok here is some more testing I did after reading all the info that was provided thanks for that.So I tested the same Dual .22 Ohms resistor with the 4 meters I have here and the Peak ESR tester I have and here are the results. It looks like the factory leads for the Brymen 869s were the problem?So the Brymen now looks good but I still hate the diode test on it so it probable will have to go.I am ready for a bench meter I am tired of turning the dial and really want a proper bench meter so now what meter do I get the Fluke / Keysight / RigolRight now I am leaning on getting the Keysight 34461A I looked at the Flukes but I think the Keysight looks like a better meter and not sure about the Rigol if I am going to spend $882 on the DM3068 might as well spend the extra on the Keysight 34461A. What's everyone's thought on this?Thanks again everyone.....

author: dolivas27
author_rank: Contributor
timestamp: February 11, 2018, 11:48:08 pm
content: nctnico thanks for the info that will save me $125 by getting the probe over the Isolation Transformer.

author: mos6502
author_rank: Frequent Contributor
timestamp: February 12, 2018, 12:01:33 am
content: But that makes no sense. How could bad probes give you alowerresistance reading than the actual resistor?

author: joeqsmith
author_rank: Super Contributor
timestamp: February 12, 2018, 01:06:21 am
content: Quote from: mos6502 on February 12, 2018, 12:01:33 amThat's a good question.It looks like the specs for the 869 in the 500 ohm range is 0.07%+10d. According to the manual, thatss +/-% of reading plus the 0.1 ohms. Then the resistor you are using is a J so another +/-5% on top of that. Lots of wiggle room but looks like the meter is fine.

author: Lightages
author_rank: Unknown
timestamp: February 12, 2018, 04:14:49 am
content: Quote from: mos6502 on February 11, 2018, 04:53:24 pmYeah.... Great advice! Fluke has never had a problem....https://www.amazon.com/Fluke-FLUKE-87-V-Digital-Multimeter/product-reviews/B0002YFD1K/ref=cm_cr_dp_d_hist_1?ie=UTF8&filterByStar=one_star&reviewerType=all_reviews#reviews-filter-bar

author: zaoka
author_rank: Frequent Contributor
timestamp: February 12, 2018, 04:38:19 am
content: I dont think Fluke 87V will make any difference to BM869 and U1273 meters. Here is what I used to do before I had LCR meter.Get these test leads or make your self ones, pull insulation from each crocodile clip and solder both clips with flexible piece of wire to eliminate intermittent problems.

author: dolivas27
author_rank: Contributor
timestamp: February 14, 2018, 10:38:38 am
content: Ok I retested with the factory leads from the Brymen again and they are still off not as bad as the first run, but they are off I am not sure why but if I flip the leads the error changes from side A to side B of the resistor.I am probably just going to sell the Brymen the diode function with no buzzer I just hate.I have decided to get the Agilent 34461A Bench Meter. Unless somebody recommends I look at something else. I figure I might as well spend the extra over the Rigol.Where would be the best place to purchase the Agilent 344561A from it does not look like TEquipment sells them?As for the other equipment I will be getting the Rigol DS1054Z (Who has the best price on this one?)On the power supply I’s looking at the Rigol DP832 also looking at the Instek GPE-3323 what's the thoughts on this unit the price is right and from what I read the unit seems to be well made?Looking to purchase everything at the end of the month. I might hold off on the meter but the other items I need now.Thanks again for the input……