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| UNI-T UT61E Multimeter teardown photos. |
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| joeqsmith:
Maybe we could modify AMPROBE's AM61E or Fluke's 61E+. No wait, those would actually be fairly robust. Best to stick with the UT61E. --- Quote from: Hydrawerk on May 14, 2016, 10:02:15 pm ---OK, so UNI-T is able to produce a good multimeter, but you cannot recognise it at the shop. :-- Oh, wait, you can buy an Amprobe meter, that is UNI-T design but with proper fuses, MOVs and PTCs. :P --- End quote --- |
| Kakalas:
--- Quote from: retiredcaps on May 13, 2016, 09:25:34 pm --- --- Quote from: Kakalas on May 13, 2016, 11:06:32 am ---Recently I noticed that UT61E began to show a false VDC (when nothing is connected shows about -1.15 VDC). --- End quote --- Questions. 1) Have you tried a new battery? 2) If you short out the probes with the meter on DCV, does it show 0.0? 3) Post clear focused pictures of your meter so we can see the pcb (both sides) and look for any obvious damage. 4) Does ACV work? 5) Does resistance work if you measure a 1k ohm resistor? --- End quote --- Hi, -> 1) Yes, I have tried a few new batteries, meter VDC readings are almost the same. -> 2) No, it doens't, see pictures bellow. -> 3) See pictures bellow, sorry for poor quality, for now I only can make photos with phone camera. I do not see any visible damage. -> 4) Yes AC works correctly, see pictures bellow -> 5) Yes resistance works correctly, see pictures bellow. I also noticed: Resistance -> buzzer function, no sound if contacts are shorted Resistance -> diode function doesn't work correctly, see pictures bellow (shows ~1,6 V when nothing connected, if contacts shorted buzzer sound apears ??? ) Capacity measurements works correctly. Frequency (AC) measurements works correctly. Current uA, mA, A measurements works correctly. :-\ higher quality: http://postimg.org/gallery/3igu9z1le/ |
| ModemHead:
@Kakalas, you probably should start your own dedicated thread in the Repair section to avoid stepping on other discussions here. Connect another DMM in parallel with the UT61E, with both in VDC mode. If the working meter indicates a "real" voltage present at the UT61E's input, then current is leaking into the front end through some fault path back to the power supply. Inspect closely for obvious stuff first: PCB contamination, wayward solder bits, carbonization from unfortunate over-voltage events. If nothing turns up, then you will have to trouble-shoot to find the source (or sink, given that the offset seems to be negative) of the fault current. Note that the inputs of the DMM ASIC are suspect due to possible internal failure of the chip. |
| Hydrawerk:
At school I found an UT61E that has some strange behaviour in capacitance mode. When nothing is connected, there is no bargraph. When I short the input, a bargraph appears and starts moving while the displayed value is OL. This is weird. Strange behaviour starts at 0:43. |
| mariush:
It's normal. In resistance mode, you're measuring the resistance of the wire and the banana plugs, the value seems normal for that wire thickness. When switching to capacitance you get the default base capacitance of around 2-300 nF. Capacitance measurements are done by the multimeter by sending short pulses of voltage to capacitor and measuring the difference between pulses. A bigger capacitor charges slower.. With a short (the wire) you're basically ever so slightly heating up the wire with each pulse and the multimeter stays at OL (overload, or no capacitor) because there's no charge on the wire, no difference for the meter to measure. You'll see the same behavior with a large capacitor (let's say 3300uF 16v) connected there, the bar at the bottom will pulsate several times at least before you get the value shown on screen. |
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