Help: UNI-T clamp multimeter DC voltage - Page 1
Forum section: electronics / beginners

author: camsmons
author_rank: Newbie
timestamp: October 20, 2022, 05:50:00 am
content: Hi, I bought the UNI-T UT216C clamp multimeter a couple years ago. Occasionally use it for household works. It had battery leaking later. It's not very bad. On PCB I only saw minor battery leaking around those 2 power connector squares. After I cleaned all of them, the multimeter worked properly. Recently when I used it to check DC voltage, found the DC voltage was not correct. 1.5V battery can be measured as 4 to 5v, and the reading keeps changing - normally descending. I have cleaned the PCB with methylated spirits again, still the same.One interesting thing I found is if I blow the PCB with hot air of hairdryer, DC voltage reading will be correct. But after the PCB is cool down, the reading is wrong again. Could anyone please help to tell where the problem could be? Thanks.

author: EPAIII
author_rank: Super Contributor
timestamp: October 21, 2022, 09:04:21 am
content: I had to look up "methylated spirits". Why not just say denatured alcohol?I would not use denatured alcohol on electronic circuits. They ADD ingredients to it to make it unfit for drinking. And not all of those ingredients are just methanol. I prefer the 91% alcohol which I get from drug stores or pharmacies. I suggest getting some of that and washing the circuit boards down with a generous amount of that several times.One thing missing in your photos is the circuitry around your range switch - the big one on the front of the meter. That switch is a prime candidate for contamination from your cleaning. The solvent you used may have itself dried up on that switch or it may have carried some other contaminate to it, then allow it to dry there. When cleaning electronics you must be worried about where the solvent may penetrate and what it may carry there and then leave there. I have learned this the hard way while trying to remove flux from repaired boards. Flush this switch many times with the 91% medical alcohol I recommended above.Finally, alcohol, regardless of the type, is not the best way of cleaning battery leakage. I would suggest a solution of baking soda applied with a cotton swab. Use several swabs dipped in the solution. A scrubbing with a small, fine bristle wire brush can be used between applications of the baking soda. Then follow that with more swabs dipped in water to clean off the baking soda. Distilled water is not necessary unless your tap water is known to be bad.Also there obviously is a missing part of the circuit in your photo. It is probably attached to that range switch and you may have contaminated it as well. So be sure to wash it down with the 91% alcohol.

author: Gyro
author_rank: Super Contributor
timestamp: October 21, 2022, 09:37:03 am
content: Quote from: EPAIII on October 21, 2022, 09:04:21 am"Methylated spirits" is what it is called in a lot of locations. It is often used because it's cheap, readily in available in DIY stores, and relatively gentle on plastics."91% Alcohol" or "medical alcohol" isEthanolpropan-2-ol, or more commonly known as IPA (Isopropyl Alcohol).The leakage from Alkaline batteries is, well... Alkaline. A solution of baking soda is also Alkaline. The only place you use it is to neutralise Acid leakage from a Lead Acid battery.For Alkaline batteries, you normally neutralise the alkaline residue with a weak acid (normally some form of Acetic) followed by distilled or deionised water and finally drying with IPA.

author: Gyro
author_rank: Super Contributor
timestamp: October 21, 2022, 10:39:24 am
content: Quote from: camsmons on October 20, 2022, 05:50:00 amIt does sound as if you have some surface leakage going on probably between a high impedance trace or pad and a supply rail. Warming the board reduce surface moisture and so inactivates the leakage. Look carefully under a magnifier for the possible extent of the spread of the battery electrolyte, eaten tracks, corrosion between IC pins etc.*You may have to disconnect the PCB, remove the LCD and give it a good flush with distilled water, shake dry, followed by Isopropyl alcohol (to bind the rest of the water) shake dry, mop with a tissue and then air dry for at least 24 hours.EDIT:*Both sides.

author: camsmons
author_rank: Newbie
timestamp: October 21, 2022, 11:20:21 am
content: Thanks. Is this one better than Isopropyl? Could be more effective than a flush?https://www.jaycar.com.au/electronic-circuit-board-cleaner-spray-can/p/NA1008?gclid=EAIaIQobChMI_vazvJfx-gIVUZhmAh1JJwgEEAQYASABEgKym_D_BwE

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 21, 2022, 11:34:53 am
content: Quote from: camsmons on October 20, 2022, 05:50:00 ammaybe something is under stress when cold. try reflowing all solder joints.

author: Gyro
author_rank: Super Contributor
timestamp: October 21, 2022, 12:12:32 pm
content: Quote from: camsmons on October 21, 2022, 11:20:21 amYes, probably. It probably won't tackle large amounts of water soluble salts though.

author: vk6zgo
author_rank: Super Contributor
timestamp: October 21, 2022, 12:57:17 pm
content: Quote from: EPAIII on October 21, 2022, 09:04:21 amThe stuff they sell as "Methylated spirits " in Oz is 95% Ethanol.It is much cheaper than the stuff you buy at Pharmacists, & just as effective for cleaning.I have read a lot of nonsense over the years about all these horrible "additives", but you aren't drinking it, for Pete's sake!Electronic equipment operates Ok for decades in situations where it is subject to dust, atmospheric pollution & humidity--a bit of "Metho" is not going to do a lot of harm!Baking soda isn't going to be much use if the batteries were alkaline ones, plus a soda deposit is going to be a worse contaminant than the few % of contaminants in Methylated spirits .

author: mrlicho
author_rank: Newbie
timestamp: May 15, 2025, 02:49:01 pm
content: Quote from: camsmons on October 20, 2022, 05:50:00 amHi camsmons! I wonder whether you were able to find what component is the one that is failing with low temperature. I'm having de same issue with the very samy clamp meter, so when I read tour post I tried heating the PCB and it worked! The clamp started measuring ok.Thanks!