Test/review of DMM UNI-T UT195DS

HKJ · 2018-05-09T14:57:57.000Z

DMM UNI-T UT195DS

This is a industrial grade DMM designed for electricians. This is the the most advanced of the meters in the 195 series.

I got it without the box, but in the pouch.

With all parts inside.

That was the meter, the probes and a Chinese manual (I could download an English version).

Probes are branded UNI-T and rated for 20A, they have very low resistance this means the 20A rating is probably good enough.

With a tip cover they are CAT IV 600V or CAT III 1000V, without CAT II 1000V (This is fairly standard for probes).

The plugs are fully shrouded, but the shroud is a bit short

The meter is a bit heavy and the range switch easy to turn, this means it can easily be used with one hand, either lying flat or standing.

All the red plastic is slightly rubberized in feel including the range switch.

The red plastic works as bumpers from any direction.

The battery/fuse compartment is sealed and due to that the lid uses 5 screws, that usual stays in the lid (i.e. no lost screws).

The flashlight led and a hanger.

Display

All the segments are shown during power on. A few symbols are not used by this meter.

Typical display during usage, it will show the number and selected measurement and sometimes the secondary display.

Secondary display functions:

In AC+DC secondary display will change between AC and DC voltage automatic.
In AC it will show frequency.
When min/max is active it will show min/max, main display shows actual value.
When Peak is active it will show peak min/max, main display shows actual value.
In frequency it will show duty cycle.

Functions

Buttons:

Range: Select manual range and change range, hold down to reactivate automatic ranging
Max/min: Capture maximum and minimum values, secondary display will show value. Hold down to disable.
Rel: Shows values relative to current value, will also select manual range. Press again to disable.
Peak: Capture peak values, this can only be used in AC modes, secondary display will show value. Hold down to disable.
Hold (Yellow): Will freeze the display reading, until pressed again.
: Turn automatic backlight off until next power cycle.
: Turn flashlight on or off.
Select (Blue): Select DC/AC in voltage and current modes, continuity and diode in ohm mode.

Rotary switch:

LoZ: Low input impedance (300kOhm), range is always 600VAC.
Off: Meter is turned off
VAC: AC voltage and peak detection, frequency is on secondary display when measuring AC.
VDC: DC voltage and AC+DC voltage
mV: AC or DC millivolt
: Ohm, continuity and diode
: Capacitance.
Hz: Logical frequency input and duty cycle.
uA: Microampere DC or AC, frequency is on secondary display when measuring AC.
mA: Milliampere DC or AC, frequency is on secondary display when measuring AC.
A: Ampere DC or AC, frequency is on secondary display when measuring AC.

Input

uAmA: Micro and milliampere input.
20ADC: 20A DC current input.
COM: The common terminal for all ranges.
xxx: All other ranges.

Measurements

Volt and frequency
- Millivolt range starts in AC
- 1V AC readings is 5% down at 20kHz (Both AC and AC+DC), rms will not work at that frequency
- 1V AC readings in LPF mode is 5% down at 600Hz, rms will not work at that frequency
- Frequency input do not require a zero crossing.
- At 1Vrms frequency input range is from 1.1Hz to 22MHz
- At 2Vrms frequency input range is stretched to 40MHz
- Duty cycle works from 1% to 90% at 100kHz with 2Vpp, precision is within 2.0.
- Duty cycle works from 1% to 99% at 100kHz with 4Vpp, precision is within 0.3.
- Default range for LPF mode is 1000VAC, but it can be changed with the RANGE switch (Mode do not support auto ranging).
- Max/min needs about 150ms to capture a voltage, auto range is disabled when using this function.
- Peak only work in AC and needs about 0.5ms to capture a voltage, auto range is disabled when using this function.
- Input impedance is 10-10.1Mohm on DC and AC
- mVDC is high impedance up to about 3V where it drops to about 100kOhm, above 12V it will drop to 3kOhm
- mVAC is the same, but capped by a 10MOhm resistor.
- LowZ is constant 300kOhm input impedance and is locked in 600VAC range.
- Input protection is 1000VDC/750VAC
Current
- 20A range has audible alarm above 20A
- 20A range is fused with a 11A/1000V 10x38mm fuse
- mAuA range is fused with a 0.6A/1000V 6x32mm fuse
- Current ranges starts in DC
Ohm, continuity, diode and capacity
- Ohm needs about 1s to measure 100ohm
- Ohm voltage is –1.1V open and –0.24mA shorted.
- Continuity is very fast (About 3ms).
- Continuity beeps when resistance is below 30ohm.
- Continuity is –3.3V open and –0.93mA shorted
- Diode range uses 3.1V, max. display is 2.800V at 0.11mA, max. current is 1.1mA shorted
- 10uF takes about 1 seconds to measure.
- 11000uF takes about 10 seconds to measure.
- Overload protection is 1000V
Miscellaneous
- Current consumption of meter is 5mA to 8.5mA depending on range (21mA with flashlight, 12mA with background light, max. 26mA).
- Meter turns off at 5V, battery symbol show at 7.2V.
- Readings will be correct until the meter turns off
- Backlight fades with dropping voltage and is mostly gone at 5.5V
- Flashlight fades slightly with dropping voltage, but is still bright when the meter turns off at 5V
- Viewing angle is good
- Display updates around 5 times/sec
- Bargraph is about 20 updates/sec
- Backlight will automatic turn on when in dark surroundings
- Flashlight will not turn off automatic, but turns off with the auto power off.
- Will automatic turn power off in about 15 minutes.
- Standard probes can nearly be fully seated in the meter.
- The meter need one or two display update to before it display the final value.
- Weight is 41g without accessories, but with battery.
- Size is 195 x 96 x 61mm
Probes
- Probe resistance 14mOhm for one, that is very low.
- Probe wire are 88cm long and feels a bit stiff, probably due to the thickness.

A look at the capacity measuring waveform with a 1uF capacitor.

Frequency input is 3Mohm to 10Mohm up to 12V where it drops to 3kOhm

mVDC is high impedance up to about 3V.

Tear down

I had to remove 6 screws to open the meter. This meter uses metal inserts for the screws and they stay in the bottom (very nice).

The flashlight, it uses two metal strips for contact to the circuit board.

The main DMM chips are hidden under a metal can.

Four small screws and for larger screws at the input terminals, then I could remove the circuit board.

To see the buttons I needed to remove 3 more screws.

A flex circuit board is used for the buttons.

I am not that happy about the can, I need to remove the display and backlight, before I can remove it.

Two screws to remove the display, solder two wires to remove the backlight and four more soldering to get the can away.

The 20A shunt (R23A & R23B) is really large in this meter, that probably means it can handle 10A for a very long time without getting too warm. The smaller current ranges are handle by two smaller resistors (R24: 1ohm & R25: 99ohm), with a diode bridge (D9..D13) and transient diode (TVS1) for protection. The voltage input has two paths, both protected with dual PTC’s (PTC1, PTC2, PTC1A1, PTC2A1) and MOV’s (SG1, SG2, SG3). The voltage path is 4 resistors (R1..R4: 4x2.5Mohm) with the optional LowZ resistor (R21: 300kohm).
There is also a lot of transistor pairs for protection mv (Q3 & Q4), ohm & capacity (Q7 & Q8 and Q5 & Q6), frequency (Q1 & Q2). There is also a pair switched into the voltage input when in the uA range (Q9 & Q10), I wonder why.
All the diodes near the battery terminals (DD1..DD6 & D4..D8) I supposed are used for coding the range switch correctly for the multimeter IC.
The two chips (U7 & U8: marked PAO) are probably voltage regulators. The larger chip (U4: ES5) is a RMS converter. Below the can we have the multimeter chip (ES222), a microprocessor (U2: EFM32ZG222F32, 32kB flash, 4kB ram), a EEPROM (U5: 24256E 32Kx8) and a LCD driver (U3: HY2613B 4x36).

The only part on this side is the LDR for automatic backlight and then there is the pads for the range switch and LCD display.

Conclusion

This meter has a lot of protection, i.e. the CAT rating is probably correct.
This meter has a good selection of ranges and functions, including peak, LowZ and flashlight. With the fairly high AC bandwidth the LPF function can also be useful. The automatic backlight looks like a useful feature. I am missing temperature and average.

This meter looks to be a rather robust meter

Notes

UNI-T do often make rebranded meters, i.e. it may exist with other names on it.

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SubLGT · 2018-05-25T13:59:26.000Z

This is a industrial grade DMM designed for electricians.

HKJ, what would be the major differences between a DMM designed for electricians, and a DMM designed for automotive technicians?

HKJ · 2018-05-25T14:12:54.000Z

SubLGT:

This is a industrial grade DMM designed for electricians.

HKJ, what would be the major differences between a DMM designed for electricians, and a DMM designed for automotive technicians?

Electricians will start in AC as default and may lack some/all current ranges. The LowZ function is also mostly for mains work. The LPF is for electric motors controlled form a VFD (Variable frequency drive), something that is used a lot in industrial installations.

Both for Automotive and Electronic the meter starts in DC and for electronic you always need the full set of current ranges.

You would also expect an electrician to use his meter at many different location and some way to hang the meter may be practical.
UNI-T has probably added the automatic backlight and flashlight to make it easier to work around machines in industrial locations.

SubLGT · 2018-05-26T14:23:05.000Z

Innova has 3 DMMs for automotive use, and one of the features they highlight is “10 MegOhm input impedance for safe automotive use”.

Is a “10 MegOhm input impedance” something unique to automotive DMMs?

Innova

3320 Auto-Ranging DMM

The Innova 3320 Auto-Ranging DMM eliminates the need to dial in the correct range when making electronic measurements. Its uses include automotive circuits, breakers, wiring, vehicle battery & charging systems, electrical components, and more.

Price: USD 41.16

HKJ · 2018-05-26T18:19:50.000Z

SubLGT:

Innova has 3 DMMs for automotive use, and one of the features they highlight is “10 MegOhm input impedance for safe automotive use”.

Is a “10 MegOhm input impedance” something unique to automotive DMMs?

Innova Auto-Ranging DMM 3320 | High-Quality Multimeter for Accurate Measurements

It is a filler specification, just about all DMM’s has 10Mohm input impedance.

bartwas78 · 2018-11-26T08:12:57.000Z

Hello HKJ.
Great review as always.
Could you try to review another UNI-T multimeter in the future.
It is UT191 series and it has few nice features, like IP65, settings memory, automatic backlight and GS/TUV certification.
There are two models UT191E and UT191T (with temperature probe and 0.1° resolution) both are 6000counts and they have big HRC fuses inside.
They are both half price of UT195DS so it maybe good alternative for electricians.
Thanks again for great work.

HKJ · 2018-11-26T08:47:08.000Z

bartwas78:

Hello HKJ.
Could you try to review another UNI-T multimeter in the future.
It is UT191 series and it has few nice features, like IP65, settings memory, automatic backlight and GS/TUV certification.
There are two models UT191E and UT191T (with temperature probe and 0.1° resolution) both are 6000counts and they have big HRC fuses inside.
They are both half price of UT195DS so it maybe good alternative for electricians.

I will put it on my list.

bartwas78 · 2018-11-28T18:54:09.000Z

Have a look at this

HKJ · 2018-11-28T19:08:19.000Z

bartwas78:

Have a look at this

I already put it on my list, you do not need to post more about it.

bartwas78 · 2018-12-07T22:17:30.000Z

I have noticed you own UT195T. Is it based on DTM0660 chip? If yes could you share its EEPROM?

HKJ · 2018-12-07T22:26:53.000Z

bartwas78:

I have noticed you own UT195T. Is it based on DTM0660 chip? If yes could you share its EEPROM?

I do not have a setup to easily read the EEPROM, that makes it a bit hard to share the contents. It is not that I have anything against sharing it, but I have a lot against using a couple of hours doing it, generally I believe my time is better used to write another review (Some will probably disagree ) .

bartwas78 · 2018-12-09T14:20:40.000Z

Hello HKJ.
There are cheap EEPROM readers with chip clamps on Aliexpress (I am using them without soldering anything).
Thanks for all the reviews, they helped me a lot in choosing the multimeters.
I have got UT191T and i have weird behaviour when measuring diode forward voltage. Open voltage is around 3V but maximum displayed voltage is around 1.2V i can easily light up any color LED including white but i am not getting any voltage reading. I am not sure if it some kind of protection UNI-T introduced in to those meters or i messed something up in EEPROM (which i have backup of but still no luck on original). Was wondering if you could tell me if you get diode readings above 1.5V and with white LED on your UT195T? Thanks for help.

HKJ · 2018-12-09T14:29:04.000Z

bartwas78:

Hello HKJ.
Was wondering if you could tell me if you get diode readings above 1.5V and with white LED on your UT195T? Thanks for help.

I do not have the T.

bartwas78 · 2018-12-09T14:52:16.000Z

On your website in article about measuring voltage i have seen it on the pictures

bartwas78 · 2018-12-09T14:52:43.000Z

Sorry, my mistake. I meant your UT195E.

HKJ · 2018-12-09T15:35:50.000Z

bartwas78:

Sorry, my mistake. I meant your UT195E.

It can show up to 3V in the diode range.

bartwas78 · 2018-12-09T15:38:42.000Z

Thank you. I suppose there is something wrong with my model then. I assume since it is showing up to 1.2V and i am getting 3V on ptobes that the problem is in DTM0660 or EEPROM somewhere.