10.
PC software![](https://www.eevblog.com/forum/testgear/uni-t-ut71d-review/?action=dlattach;attach=93283;image)
The meter comes standard with a USB RS232 cable with an optical connection module.
The software may seem pretty contrived at first, but its functionality is quite acceptable, after some experimentation.
Toggle the ‘USB connect’ soft button to stop and start your logging session.
Values can be entered in the Min/Max windows for aural exceedance warning.
Tick the ‘Repeat’ function to suppress non-changing measurements.
Enter your required sampling interval in seconds in the next window.
Afterwards, the log can be saved as an Excel worksheet or sent to a printer.
Use the ‘Recall data’ feature when you want to retrieve data from the meter’s internal memory. You can set a start time to match the original capture if you wish and also match the logging interval of the original data capture .
The graph is the most frustrating. You have to use your mouse to select the area of interest. Drag right with the left mouse button pushed in to select a small window and when you’re done, drag left to zoom out to the original graph.
Hold the right mouse button in and drag to reposition your viewing window.
Tick ‘Fill’ for a blue bar graph instead of a continuous line.
Choose a number of points per page if required and press ‘+’ to enlarge the graph window.
Multiple meter logging is possible, in two separate windows.
Fast logging (8 samples per second) in real time is possible, wen the meter is in 4,000 count mode.
11.
ComponentsU1 ES51966P Cyrustek dual-slope ADC
U2 M430F149 micro controller TI
U3 U9 HT1621B Holtek LCD controller x2
U4 Opamp STEZ832 062C (thermocouple cold junction circuit)
U5 ES636 (AD636J) TRMS to DC converter 1% error, crest 6 (Cav=10uF)
U6 Dual Opamp STEZ832 062C (frequency circuit)
U7 Voltage regulator 5.5V
U8 Voltage regulator 3.5V
U10 24LC515H Memory microchip CMOS I2C Serial EEPROM 512K
U11 HCF4011 Multiplex NAND gates AESA
U12 Maxim MAX6190A bandgap voltage reference 2ppm/C 1.25V 50ppm/1000hrs
U13 Dual Opamp ST7444 72C (TRMS circuit)
U14 Precision Opamp OP1177 AO47 (V Ref circuit)
1 PTC (WMZ11-75HV 1.1K)
2 Crystal Oscillators (4 MHz for the ADC and 32 kHz for the TI uC)
8 Precision metal film resistors 1W TCA5C6 (4x2.5M and 1M11, 101K, 10K1, 1K01) (0.05% resistance tolerance and 10ppm/C). More recent boards (from REV6) have SMD precision resistors instead, replacing the through hole resistor network.
![](https://www.eevblog.com/forum/testgear/uni-t-ut71d-review/?action=dlattach;attach=93285;image)
![](https://www.eevblog.com/forum/testgear/uni-t-ut71d-review/?action=dlattach;attach=135471;image)
12.
ValueNowadays, the UT71D meter sells for about 135.00 USD, including shipping costs on eBay, from Hong Kong and China sellers.
I still haven’t found another meter that comes close to the specifications and features of this UNI-T, at this price point.
13.
VariantsThey were a few rebranded meters available in Europe and the US, but I think that most have been discontinued by now.
It is still possible to find a Tenma, Voltcraft and a few others on numerous internet sites, but not necessarily with the same set of features as the originals.
![](https://www.eevblog.com/forum/testgear/uni-t-ut71d-review/?action=dlattach;attach=93295;image)
![](https://www.eevblog.com/forum/testgear/uni-t-ut71d-review/?action=dlattach;attach=93297;image)
14.
ModificationsThere usually is space for HRC fuses and an MOV/spark gap on the board, but while probably made safer, doesn’t necessarily meet the latest safety regulations.
There have been several board revisions over the years, so this may not be always feasible, depending on the PCB configuration.
I didn't bother modifying the 71D and I would advise against it if you only work with low power circuits, like I am. I soldered a few extra bits in the 71B, but it was more for the fun of the exercise rather that a quest for total safety.
Here is a picture of the modifications on my 71B:
15.
CriticismsHere are most of the perceived flaws mentioned by some owners. While some are justified, others might just be nit-picking.
The reflective LCD curved acrylic cover was mentioned a few times as a nuisance in rooms with multiple light sources.
The lack of a blank insert for the USB plug recess was also criticized. The one provided with the UT61 is a perfect fit though.
It has an irritatingly slow continuity, but at least the signal is latched.
I did find a way to achieve a faster continuity test which doesn't involve any modifications:
1. Turn the range switch to Ohm and select the diode mode by pressing the blue button twice. You are now in the 4V range.
2. Press the RANGE/SETUP button until the meter beeps and displays OFF in the 'low' setting.
3. Press the HOLD button once to access the count display.
4. Press the HOLD button repeatedly to select each number in turn.
5. Change each number with the + and - buttons until your display reads 27400 or slightly lower and press EXIT to store it.
6. You are now in a fast mode for your continuity testing, staying in the diode range.
7. When you are done with the continuity testing, press RANGE/SETUP until it beeps again, then press STORE to display OFF in the low mode.
8. Press EXIT to return the meter to its usual state.
It is a bit of a convoluted procedure, but at least the function is available if you don't have another meter at hand.
Of course, the glass fuses elicited a lot of scorn, but, at the time of production, high voltage HRC fuses were not a safety requirement. On the positive side, if you blow them regularly, they are dirt cheap to replace.
The bale angle is sometimes considered too shallow. 30 degree from horizontal, which is fine for me.
It has a too slow LCD update rate for some, with one refresh per 2-3 seconds. (My Gossen 26S behaves the same way)
The battery compartment is too tight for comfort. It is a tight fit, but no enough to provoke lasting frustration, in my view.
The meter is fragile and may not survive a drop test. Probably true, but for electronic work, if kept on the bench, it should be relatively safe from any damage.
16.
ConclusionI never regretted buying these two meters and although I have acquired a few more ‘respectable’ ones since then, I still reach for the 71s on a regular basis.
I think they have tremendous value for money and are ideal for hobbyists who don’t want to spend a fortune on top-end meters and their optional logging accessories.
Of course, they are not perfect by any means, but UNI-T managed to produce a dependable full-featured meter, at an affordable price.
The inaccuracies on low ACA are a concern, especially on the 71E, so keep that in mind if you're considering buying one of those meters.
Hopefully, the next version will be even better and will comply fully with the latest safety regulations.
Martin Lorton's review:
![](https://www.eevblog.com/forum/testgear/uni-t-ut71d-review/?action=dlattach;attach=93293;image)