User experience of Uni Trend UT71D - Page 1
Forum section: electronics / general

author: nukie
author_rank: Frequent Contributor
timestamp: March 11, 2012, 02:28:35 am
content: Keep away from mainsAnyway, I've been refraining myself from posting because I own a UT71D from Oct 2007. But, if you search hard enough, you will soon realise that UT71A/B/C/D shares the same PCB, whereas the E is slightly different design on the top area. So I think they are based on the same platform, given the fact that Chinese like to cut corners, there's no way they design a totally new PCB to add a few extra features. There are a few versions of UT71A/B/C/D PCB. The changes made is just to move the current shunt away from the terminals. On my first version the current shunt is dangerously close to the terminals. It's like 1-2mm gap. You never know which version you got until you tear it up.Cut a tape and mask the last digitI believe the 71 series is the flagship models. During the 4 years of ownership, I have been disappointed with my purchase. This is not something a 10 minute video review can tell you. It's all the little bugs that you find out from day to day use. I use the 71D along with Fluke 187 and 189. Also a few cheap $30 meters. You paid that much for a meter you will expect that it perform close to highend multimeters but no. The last digit is always unusable. It's never stable and unrepeatable.Don't measure pulse DCV under 10KHzI have posted before, how a square/triangle wave affects the DCV reading of the UT71D under 10KHz. It will only be stable for frequency 50Hz, 100Hz, 150Hz, 200Hz, 250Hz...10Khz. Anything in between, it's not going to work. For eg, you get weird DCV readings for 8.32Khz, the filtering just fails to work. I have made several attempts to contact Uni-T engineers. I have been told they are trying to fix the problem, the last time I tried, they told me to get another meter. The 71D is not suitable for the job. So I use my Jaycar $30 meter which reads the pulse signal just fine along with the Fluke brothers.Calibrate frequentlyThe meter was highly accurate when it was new. 2 years in to ownership, I decided to check it's calibration. I have three 34401A all built in the 90s, a Keithley 2000, Philips 2535 so I am pretty sure my collection of voltage references is pretty spot on. The UT71D drifted more than accepted but you would argue it's time for a yearly calibration. My older $30 meter drifted less than the 71D in 5 years compared to the same range/digits. 4 years into ownership, it got worse. I took the readings during different time of the year, so the temperature could play a part on the reading, but if the $30 meter didn't drift, the same range/digits on the UT71 shouldn't.Buy it at your own riskI have not tested other functions, my work revolves around DC-DC power supplies I measure in the range of uV to 50V. I use the DCV function mostly on sense resistors for current measurement. It's my lab permanent resident, so it always lived a comfy life of 23c I don't know how it will hold up to the outside environment.Now it gets really confusing... for prospective buyers anyway.I have to say, the case design is really well done. It's nice to hold and the weight(light 9V battery) is just right. The stand is loose it rattles, a trademark of Chinese crappy plastic molding process. Other than that, the fit and finish is excellent, the gap around the two piece case is consistent. The function switchis robust after 4 years of use, but I have to admit it mainly travelled one step to the DCV function. I always wish there's a on/off switch on a multimeter so I won't wear out the function switch. Battery life is excellent, never gave me a problem.I don't know why people rave about this meter so much. I was cheap & naive I bought it and I regretted for the performance degrade(drift) after two years. Please note, it has been many years since I bought the meter, they may have updated the meter. It's very expensive meter for what it is. I DON'T RECOMMEND BUYING IT mainly due to the price.I see the UT61 series a better choice, the Chinese community has done some extensive test, it has very impressive linearity. I can't remember if it's D or E.One day I was curious so I removed the shield and revealed the resistor attenuator/divider network. I am glad to report that the UT71D sports some 10ppm tempco thin film resistors. According to the resistors datasheet anyway. I am going to remove them one day and test the real TC of these Chinese made babies. I will report back when I have the results.The last two pictures are custom Fluke 187 'hybrid ceramic?' resistor network. I don't know if it's made by Caddock, I have seen this in earlier Fluke products such as the 8050A with a few ICs on it.

author: T4P
author_rank: Super Contributor
timestamp: March 11, 2012, 10:48:30 am
content: Yes yes , i understand .I love the 61 series because i have been given a try in my local store .71 series will make me consider for a while since it has more counts , but heyho , i will wait for the day the 71 is fixed .Can't wait for that day .