Bad multimeter? - Page 1
Forum section: electronics / beginners

author: germanshep
author_rank: Newbie
timestamp: August 30, 2021, 04:44:55 pm
content: Hello. I am getting back into electronics after receiving an Associate Degree 28 years ago but going into computers as a career instead.I have 2 Fluke meters that I keep on the bench. One is a 29 Series II from school 28 years ago and is still 100% accurate. I bought a new Southwire 14090T for household electrical work. The mA fuse showed as blown when using the probe to check the mA socket. Ordered a fuse, took the meter apart, and it still won't register continuity with a new fuse putting the probe in the mA socket. Amps measures fine. So there is an issue with the meter itself. Please find the attached pic - sorry it is a bit blurry.My question is, the meter measures eveything else fine, although I have not tried to measure current past the mA range limit. But do you think I should stop using this meter in case there is more wrong under the hood? I chose this CAT IV meter for safety reasons and the bluetooth function. I don't want to risk my safety and would appreciate opinions on whether I should even use this meter at all...I love this blog and thank everyone for their input and insights. I've learned a lot and am excited to put my degree to use. (Finally)Jeff

author: Manul
author_rank: Super Contributor
timestamp: August 30, 2021, 06:51:07 pm
content: It was not really clear from the decription, does mA work or no? I mean, does it measure current? If it does, just forget about it, because it might be that rotary switch disconnects the terminal while in other modes or something like that.

author: bob91343
author_rank: Super Contributor
timestamp: August 30, 2021, 06:53:43 pm
content: I think you should use the COM and Ohms jacks.

author: joeqsmith
author_rank: Super Contributor
timestamp: August 30, 2021, 06:55:09 pm
content: From your picture, it appears you have the meter in continuity mode, not resistance. It may be out of range is all.

author: Gyro
author_rank: Super Contributor
timestamp: August 30, 2021, 06:58:06 pm
content: Welcome to the forum.Does the manual specifically tell you that you can check the mA fuse continuity that way?The 10A range, due to the high current, has the shunt and series fuse permanently connected between the 10A terminal and Common. The manually switched mA / uA ranges use multiple shunt resistors, going through the switch contacts.Moving my head quickly to compensate the camera shake (), it looks as if you have the meter set to the (low resistance range) continuity setting, this is probably too low to register the shunt resistor for the uA range, which could be several k ohms. Obviously the knob can't be in two positions at once so I suspect that the shunt setting defaults to the highest value (lowest current range) shunt resistor.The way to check it is to use a second meter to check continuity, with the meter under test set to its highest mA range. The second meter should then be able to read the fuse + mA shunt resistor in series.

author: Monkeh
author_rank: Super Contributor
timestamp: August 30, 2021, 07:06:27 pm
content: It's likely neither shunt is in circuit when the switch is not in the requisite position, so you will be unable to test the fuse this way. Your old Fluke, having only the one shunt for that jack, would leave it connected and allow such a test.

author: BrokenYugo
author_rank: Super Contributor
timestamp: August 30, 2021, 07:55:39 pm
content: Use the fluke in diode mode as a current source to test the low current measurement of the meter in question, should be around 1mA/1000uA, spec will be in the Fluke meter's manual.

author: germanshep
author_rank: Newbie
timestamp: August 30, 2021, 09:21:14 pm
content: Here is a picture of the A jack with a good quick probe fuse check. I didn't realize I was on continuity when I used the probe for the internal mA jack check, but confirmed that it reads OL on both auto ranging and continuity and tests fine on the A jack on both range selections. I was taught this method for simple quick fuse checks while attending school nearly 30 years ago.I never thought of testing the meter's low current with my Fluke's diode mode.. Thanks for the suggestion.I did test the Southwire's fuse initially, so there must be something going on internally with the unit. I was also thinking faulty range switch or if I'm lucky, a bad solder joint.. I really didn't want to take it apart as it is IP67 rated, but guess I've got nothing to lose. It was an Ebay meter purchased new and sealed in retail clamshell packaging but not from an authorized retailer. I bought a simple Amprobe AM-420 for battery and low voltage checks 2 months before that and the 9V test selection decided to stop working.I think in the future I will simply pay a bit extra for the factory warranty by going through an authorized retailer and just stick with Fluke.Thanks for the input.

author: Monkeh
author_rank: Super Contributor
timestamp: August 30, 2021, 09:23:31 pm
content: Again, as it has two current shunts the switch almost certainly must be in the uA or mA position to connect them - you will not get continuity while in the continuity position. Do not take it apart, just check the resistance using a different meter while the unit has the appropriate range selected.

author: germanshep
author_rank: Newbie
timestamp: August 30, 2021, 09:49:45 pm
content: Quote from: Monkeh on August 30, 2021, 09:23:31 pmThank you - That did work.I will take actual low current measurements tonight when I get time and see what results I get.Interestingly enough, all of my meters have internally tested fuses successfully the "old school" way. This meter is the first to not do so but I did learn this trick 30 years ago.. Thankfully Ohm's Law is a constant!