Author Topic: UT71C and UT60E vs. DMM Check Plus  (Read 5806 times)

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Offline arcom

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UT71C and UT60E vs. DMM Check Plus
« on: March 28, 2014, 08:10:44 am »
I've "stolen" a DMM Check yesterday from my colleague and decided to check the accuracy of my multimeters. I have two UT71C meters which I rarely use and one UT60E that I use most of the time. Only one UT71C was tested. Surprisingly enough, accuracy was better than expected for the lower priced UT60E while the UT71C was...well...a bit on the edge of its specs for some measurements. All measurements were taken at room temperature (approx. 21C/70F), 30 minutes after being powered on.

Spec sheet for the DMMCheck Plus:


First up, the UT60E, 4000 count TrueRMS multimeter. Scratches on the screen are actually on the protective foil. Yes, it's still there, after 5 years of use. Haven't really noticed it until yesterday while taking pictures ;D

AC/DC voltage measurement: within specifications.


AC/DC current measurement: unbelievably spot on!


Frequency and duty cycle: within specifications.


Resistance measurement: again, spot on!




Next up is the better spec'd UT71C, a 40000 count TrueRMS multimeter with data logging, min/max, reative measurements, blah blah... I have to mention that the current measurements fluctuated a bit whenever the backlight was turned on. Most likely the LEDs take a lot of current and that affects the reference. It's probably a good time to replace the battery.

AC/DC voltage measurement: within specifications.


AC/DC current measurement: AC failed, DC passed (barely).


Frequency and duty cycle: within specifications.


Resistance measurement: almost spot on.




All images are linked from my web site so in case you don't see them, you can check the blog posts here:
UNI-T UT60E Accuracy Check
UNI-T UT71C Accuracy Check

I hope this will help some of you who are thinking of buying one of these meters. I know that the UT61E is popular around here, but his older brother UT60E is also very very good. Next up is the Fluke 287.
 

Offline TMM

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Re: UT71C and UT60E vs. DMM Check Plus
« Reply #1 on: March 28, 2014, 09:48:47 am »
Was the residual reading zero on ac current?
« Last Edit: March 28, 2014, 09:51:40 am by TMM »
 

Offline arcom

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Re: UT71C and UT60E vs. DMM Check Plus
« Reply #2 on: March 28, 2014, 10:36:02 am »
Good question! I don't remember but will check it later, when I come home. Although I'm pretty sure that it was.
 

Offline Wytnucls

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Re: UT71C and UT60E vs. DMM Check Plus
« Reply #3 on: March 28, 2014, 12:56:41 pm »
A couple of things you missed in the specifications of the UT-71C:
True RMS readings are only accurate from 10% to 100% of the range. (You tried to measure 1mA AC on the 40mA range)
When the frequency is lower than 100kHz, the quoted accuracy is also only valid from 10% to 100% of the range.
 

Offline Wytnucls

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Re: UT71C and UT60E vs. DMM Check Plus
« Reply #4 on: March 28, 2014, 01:04:10 pm »
Here is my 71D measuring ~10mA AC+DC from a function gen sine wave @ 100Hz.
The screen backlight has no influence on the readings.
Accuracy: 0.7% of reading+15 (If AC+DC, add 1%+35)
The 71D has the original factory calibration

« Last Edit: April 13, 2014, 03:32:34 pm by Wytnucls »
 

Offline arcom

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Re: UT71C and UT60E vs. DMM Check Plus
« Reply #5 on: March 28, 2014, 01:21:45 pm »
Indeed, you are correct. It helps to RTFM every now and then :)
In that case, AC current reading is also within specs (factory calibration; meters are over 3 years old).

I will measure AC/DC current with both meters in series and also check the backlight influence for each multimeter. I'm sure that the readings dropped whenever I switched the backlight on.
 

Online Rick Law

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Re: UT71C and UT60E vs. DMM Check Plus
« Reply #6 on: March 28, 2014, 04:51:43 pm »
I found the DMM-plus DC volt very temperature stable.

When I first got it from the mail, it was outdoor temperature (between 10 to 20F / -12C to -7C), I immediately did all the measurements with my UT61e.  Two hours later when DMM-plus reached room temperature (72F/22C) and I did all the measurement again.

-----------------------------------
For the DMM temperature change from 10-20F to 70-75F
-----------------------------------
DC Volt - no change 4.991V
mA - no chage 0.998mA
AC Volt - 5.156ACV change to 5.164ACV

Resistors - no change except last digit  (didn't note the exact value before I made adjustment)

AC Frequency - last digit +-1
  10.000KHz no change (first frequency)
      47.7% duty changed to 47.3%
  20.000KHz to 20.001KHz (optional second frequency)
      49.5% duty no change at 49.5%

(The 10.000KHz for AC frequency was my mistake, I since had it recalibrated back to 100Hz)

I proceeded to adjust my UT61e and made that read exactly 5.000V which drifted to 4.999V within the hour.  It has been reported that merely the act of reclosing the UT61e cover was enough to affect the reading.  So, I left it at 4.999V.  The UT61e was around 1 year old.
 

Offline Wytnucls

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Re: UT71C and UT60E vs. DMM Check Plus
« Reply #7 on: March 28, 2014, 04:55:43 pm »
Another limitation to keep in mind is the AC bandwidth on AC current.
The UT60E is inaccurate above 400Hz.
The UT71C is all good up to 10kHz.

Check the readings for the Gossen and UNI-T meters:
« Last Edit: March 28, 2014, 05:00:24 pm by Wytnucls »
 

Offline Talha Arif

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Re: UT71C and UT60E vs. DMM Check Plus
« Reply #8 on: February 08, 2019, 11:53:10 am »
What is the meaning of 10% to 100% accurate on Trms AC for UT71C... also is that better to use??? I've a problem... it doesn't measure dutycycle % of XL4015 (@150kHz)...
 


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