Uni-T 71 Data Logging

[Wytnucls]

I thought someone might be interested in the datalogging capability of these multimeters.
Here is a screen shot of 2 Uni-T 71B/D models hooked up to the same computer recording in real time 2 sets of parameters in a circuit, using the same computer time base.
The data can then be saved to an Excel spreadsheet.
Of course, the data can be saved in internal memory instead. 10,000 samples in the D model, 100 in the B model. The drawback is that there will be no time base to synchronize the data afterwards.
Sampling period is between 1 and 250 seconds.
Battery life with a 9V zinc/carbon 6F22 400 mAh is about 50 hours of continuous use.

[Bored@Work]

If you search the forum you will find that the UT-71 was discussed before, including pointers to pictures of the inside. Lets just say it didn't impress.

[Wytnucls]

I have read all that was written about the 71, on this site and some others. I think the meter got a bit of a bad wrap, the main gripe being the lack of beefy fuses and flimsy input protection.
As a benchtop meter, working with low power circuits,  it does a pretty good job.
It is certainly not one I would throw carelessly in my toolbox.

[Wytnucls]

Oh, and don't try to measure accurate average DC voltage on a square wave signal below 100Hz. Looks like the meter wasn't designed for that.
Strangely, most meters can do the measurement from 10Hz onward, even my $10.00 Victor VC921 pocket DMM. 

Also, in the manual it states:
The requirement of input amplitude for duty cycle measurement is as follows: When between 10Hz and 40MHz: 200 mV to 30V RMS.
Where in fact, using a Rigol function gen, I can confirm that one can only measure square wave duty cycle between 10Hz and 3.7kHz.
Probably a misprint in the manual, 40MHz instead of 4.0kHz.

Frequency measurement is fine between 2hz and the max I could test on the Rigol, 5MHz.

The 4~20 mA loop current measurement as % readout works as advertised

[Wytnucls]

Here is a picture of the latest 71D PCB, which is quite different from the previous ones I have seen.
Beefy 3W resistor by the 10A input.
Same glass fuses though..

[Mechatrommer]

ok thats interesting! thats what a man do, to tear it apart! it will be more interesting if you can post photo of close up (bigger picture) at the blue colored region, specifically what opamp is that and the components its below left (arrowed)? thank you! in advance.

[Wytnucls]

Here you go:
3 ST OpAmps: 2 062C 1 072C
a bunch of resistors

[Wytnucls]

Here is one for the Uni-T 61E owners: 

[T4P]

What's the probe that came with it? googling UT71E comes up with this one

I assume it shouldn't be right?
because the ones from china ( where they are supposed to be from )
are giving these

[Wytnucls]

My 71B from Shanghai, came with the light ones in your first picture, rated Cat III 1000V 16A
My 71D from Hong Kong, came with the darker ones in your second picture, rated Cat IV 600V 10A

The light color ones are better, with unnmarked soft silicone leads, similar to the Flukes.
The second darker model has stiffer PVC leads, marked Herwell 18AWG 2000V 80c

[Mechatrommer]

Here you go:
3 ST OpAmps: 2 062C 1 072C
a bunch of resistors

you are the man! thanks! i own UT71A but i dont use the software for any usefull purpose yet. maybe someday. and getting to the other side of the board is not simple, we need to desolder something i guess.

[T4P]

My 71B from Shanghai, came with the light ones in your first picture, rated Cat III 1000V 16A
My 71D from Hong Kong, came with the darker ones in your second picture, rated Cat IV 600V 10A

The light color ones are better, with unnmarked soft silicone leads, similar to the Flukes.
The second darker model has stiffer PVC leads, marked Herwell 18AWG 2000V 80c

The light grey ones look better and perform beter BUT ... UNI-T no longer sells them ... Only the UT-L16 which i don't see it coming with any product
I would think it would come with the UT805 (Don't bother searching that one it's a 5-1/2d Bench DMM but as with most UNI-T bench products it's probably crap) but no ...
Anyway the UT-L16 looks good, looks like a agilent probe

[Wytnucls]

Here is the other side of the board:
Main processor is Cyrustek ES51966
http://www.cyrustek.com.tw/spec/ES51966.pdf

[Mechatrommer]

thanks man!
1) you confirmed there's no other main mcu other than the ES51966.
2) do you have to desolder something to get it apart? or push in the probe hole hard?

[T4P]

Nope, it's still the ADC
the main processor is the HT1621
http://pdf1.alldatasheet.com/datasheet-pdf/view/64418/HOLTEK/HT1621/+4_429UELIy.lcKXBwvY+/datasheet.pdf

[Mechatrommer]

now i get it. i thought it was a logic or ram chip etc.

[Wytnucls]

Holtek HT1621 is the LCD controller.
The main chip, all in one DMM ADC, is the Cyrustek ES51966.

There is no need to desolder anything. The board comes out with a bit of pressure on the probe tubes.

[Mechatrommer]

but it got 3wire serial IO, maybe it also controlling connection to PC. sorry i'm too lazy to check the datashit in detail.

[Wytnucls]

The micro controller must be the TI LSD0007, under the shield.
Same as the one in the Fluke 287/289!

[T4P]

Oops. Googling that reveals it's a MSP430V103IP
Quite a lot of uC for a $150 meter

[Wytnucls]

Here it is:

The Texas Instruments MSP430 is supposed to be the best low power microcontroller around.
How do these currents compare with other DMM?

2.5mA for Hz/%
3.5mA DC V and mV
3.7mA Send (IR) VDC
5.0mA Continuity (Latched)
5.2mA Diode/Resistor
5.4mA Caps
8.3mA Temp/uA/mA/A

Add 5.3mA for backlight low and 9.8mA for backlight high

Battery warning 6.8V
Minimum reliable VDC measurement charge +/- 5V

[T4P]

I don't think it's because of the uC, rather the LCD driver and the LCD/ LCD or the ADC
I posted my current measurements of the UT61E on the UT61E thread so yeah

[Wytnucls]

Yes, Dave was saying his Fluke 87 manages 1.1 mA on DC Volt measurement. I guess the LCD is the hog on the 71...
The backlight is good though, about 2/3 lower consumption than the Fluke, for similar effect.

[Mechatrommer]

Oops. Googling that reveals it's a MSP430V103IP

you didnt mean that it is the...
https://estore.ti.com/MSP-EXP430G2-MSP430-LaunchPad-Value-Line-Development-kit-P2031.aspx
that was famous here sometime ago? are you not joking?

[T4P]

Oops. Googling that reveals it's a MSP430V103IP

you didnt mean that it is the...
https://estore.ti.com/MSP-EXP430G2-MSP430-LaunchPad-Value-Line-Development-kit-P2031.aspx
that was famous here sometime ago? are you not joking?

Different chip leh bro  . The MSP430 uses the Value-line DIP/SOIC series, this one is a TQFP chip. Different beast entirely i believe! In fact TI doesn't even recognize the V103, maybe it's a "spin-off" series but it's definitely only searchable in china ... i leave it to you to guess what it is

[Wytnucls]

The TI LSD0007 uC chip is available in Hong Kong for USD 5.50 per unit (batch of 100)
The TI part number is TI M430F149 QFP-64