EEVblog Brymen BM235 TEST INTERNAL BATS? - Page 1
Forum section: electronics / testgear

author: MacMeter
author_rank: Frequent Contributor
timestamp: February 22, 2017, 08:13:11 pm
content: Lots to learn when getting your first quality DMM. As always, I looked before posting, their are some online generic instructions, like Fluke for example, that quickly explain how to use the test leads in the input jacks to tell if BOTH internal fuses are OK. But I have not been able to make it work on the rebadged Brymen BM235.The BM235 manual says:"Battery and Fuse replacement:Both fuses can be tested by inserting a probe into the A or mA/uA jack. If the IrEr warning message and beep is not displayed, then the fuse on that input is blown."Which probe, what end, tip or connection side, and on what meter setting?If someone has the time to explain, in newbie detail, I'd appreciate it.What setting should the meters dial be set to to begin the test?What probes or probe should be used?What jack should the connection end of the probe/probes be placed in?Now in what jack should the probe TIPS be inserted to?Once all that is done properly, what are the expected on screen results for GOOD, or BAD fuse results?I know this is kids stuff for you meter buffs, but I'm stumped.THANKS!

author: Ranayna
author_rank: Super Contributor
timestamp: February 22, 2017, 08:59:27 pm
content: Just verified with my BM235 that i got last week.The BM235 has the nice feature of warning you when a probe is plugged in to an amps jack and you are not in amps measuring mode.As the meter has very low resistance between the common and either of the amps jacks, this warning can save you from blowing up you meter, when you try to measure a voltage while having the probes in the amps socket.This feature seems to also work as fuse test. Just plug any lead into either the A or mA jack, don't connect the probe tip to anything and switch the meter to any non amps measuring mode. If it does not beep at you, the fuse is broken.This works, since the socket is split into tho isolated sections that get connected when you insert the probe. That way the meter can detect the wrong connection.EDIT: Typo and clarification

author: tooki
author_rank: Super Contributor
timestamp: February 23, 2017, 09:46:59 am
content: So exactly the same as the Fluke 87V for example.

author: MacMeter
author_rank: Frequent Contributor
timestamp: February 24, 2017, 12:50:44 am
content: Quote from: Ranayna on February 22, 2017, 08:59:27 pmThanks, I was aware of the input jack warning, but since it only worked on the 10a input and my meter is new, I was confused. As it turns out, the small .4 a. was blown, so NO response, so indeed there was nothing on the display, working properly.Since I have not done any current readings in either jack, either the fuse was NG before, and I did not know it, or I blew it by trying different leads in different jacks. Though I'm NOT even sure if one can blow either fuse just by inserting the probes in the two current jacks. Or maybe the fuse can be blown by moving the selector switch with the probes in an AC outlet, and being on the wrong setting. I really have no idea what I may have done, if anythin, but lucky enough my 5 pack, (now a 4 pack) of 400ma fuses came in the day before.What I was referring to regarding checking the internal fuses with the test leads, is not shown in the BM235 manual, but shown in the Fluke 87V manual, which I found online. You can test the ohm readings of the internal fuses, put the meter in OHM mode, use the positive lead in its normal jack, use the lead tip in both of the current jacks, the Fluke manual shows you what ohm range readings you will get. The tricky part is to get the tip to connect to side of the input jack, it's a bit finicky, but can be done. I suppose it's safe since it's shown in the Fluke manual, so I doubt my original poking around with the test leads blew my fuse, but who knows?

author: IanB
author_rank: Super Contributor
timestamp: February 24, 2017, 01:22:13 am
content: Quote from: MacMeter on February 24, 2017, 12:50:44 amEven though it will work with a Fluke 87V, that doesn't automatically mean it will work with a different meter. Not every meter may have the same internal design and circuitry.

author: IanB
author_rank: Super Contributor
timestamp: February 24, 2017, 01:25:04 am
content: By the way, a reliable method to test if the fuses are good on the BM235 and other meters is to remove the fuses from the meter and test them with the meter on the resistance range. If the fuse is good it will have a typical low resistance, if the fuse is bad it will read open circuit.

author: MacMeter
author_rank: Frequent Contributor
timestamp: February 24, 2017, 01:53:01 am
content: Quote from: IanB on February 24, 2017, 01:25:04 amIndeed, but that's the obvious way to test any fuse. If you don't want to remove the meter from the rubber bumper case, and then unscrew the back cover, the fluke lead tip instructions work on the BM235, I tested it, ohms matched the expected outcome. But if you don't need the ohms result, and just want test if the batteries are good, using the input jack warning detection seems easier still, and you don't have to worry about making the lead tips connect to the internal side of the current jacks, and probably better then inserting those sharp tipped probes in those jacks in the first place.