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| UNI-T UT61E Multimeter teardown photos. |
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| Nisei:
Correct, TL175 I got them with my Fluke 177. Sold the 177 but kept the TL175 leads. I really like them. |
| mos6502:
--- Quote from: naughtilus on August 23, 2015, 07:41:38 am ---Only issue is if you have pitted and/or dirty leads, which they usually are even when new out of the box. Cleaning them with contact spray helps a lot. --- End quote --- Had the same problem. Tried all kinds of chemicals. Acetone. Alcohol. Window cleaner. It helped a little, but it wasn't 100%. Then I tried this: (A small brass wire brush.) Scrub scrub scrub. Result: PERFECT. When I rub the probes together in buzzer mode, the resistance never even goes above 0.2 Ohms. Before, when did the same thing, the resistance would spike to hundreds of ohms. The formerly shitty Uni-T probes are a joy to use now. |
| naughtilus:
Great idea with the brush. :-+ The stock leads are not great, but certainly not terrible like the ones found on 830 DMMs. |
| ocw:
I haven't seen much information on the sensitivity of the frequency counter in the UT61E other than it's not the best. The manufacturer rating of 220 MHz along with the meter's banana plug input is a bit of a oxymoron. 220 MHz and the normal banana plug leads don't get along. So, I made a banana plug to BNC shielded cable. I fed the output of a Ramsey COM3010 service monitor directly to the meter when its 0 dBm output level was adequate. When needed, I added a 16 dB amplifier. It's 40 mW output was inadequate above 101 MHz. Even starting below that frequency, greater frequency resolution is generally required dictating use of a frequency counter anyway. I measured the sensitivity of the frequency counter portion of the UT61E as: UT61E FREQ COUNTER SENSITIVITY 1 Hz >3.43 V > +24 dBm 2 Hz 171 mV -2.3 dBm 10 Hz 105 mV -6.6 dBm 60 Hz 105 mV -6.6 dBm 1 kHz 105 mV -6.6 dBm 10 kHz 117 mV -6.0 dBm 100 kHz 117 mV -6.0 dBm 0.5 MHz 165 mV -2.6 dBm 1 MHz 165 mV -2.6 dBm 4 MHz 200 mV -1.0 dBm 12 MHz 243 mV +0.7 dBm 25 MHz 243 mV +0.7 dBm 30 MHz 243 mV +0.7 dBm 35 MHz 243 mV +0.7 dBm 40 MHz 267 mV +1.5 dBm 50 MHz 385 mV +4.7 dBm 60 MHz 385 mV +4.7 dBm 65 MHz 554 mV +7.9 dBm 70 MHz 777 mV +10.8 dBm 75 MHz 873 mV +11.9 dBm 80 MHz 873 mV +11.9 dBm 85 MHz 1.10 V +13.8 dBm 100 MHz 1.20 V +14.6 dBm 101 MHz 1.35 V +15.6 dBm Given the low resolution of the counter I didn't go into detail confirming its accuracy, but I never saw a sign of any significant error. I also measured the frequency response of the AC voltmeter portion of the meter. Since I'm more concerned about its validity for frequency response measurements, I measured the response +/- 1 dB. I found that to be 5 Hz to 68 kHz. The response was down 1 dB at 5 Hz and up 1 dB at 68 kHz. At 60 Hz I measured its AC voltage accuracy as +0.155% (well within its 0.8%+10 rating). |
| mos6502:
ocw, that's very interesting. I think above a few MHz, the capacitance of the leads becomes a big issue. Have you tried using extremely short leads? Or a BNC to banana Adapter? Here's a schematic of the UT61E: http://docdro.id/EbNqMPt As you can see, the input circuitry of the frequency counter is very simple (the stuff around R35). I'm having some issues with the frequency input of my UT139C, but it did measure up to 27MHz correctly, even though it's only spec'd to 10MHz. Have you tried the duty cycle measurement? It would be interesting to know up to what frequency that would be halfway accurate. |
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