UT-81B multimeter/oscilloscope

UT81B from Uni-Trend is a scopemeter. It is a multimeter with some basic oscilloscope functions.

This multimeter can measure what you expect from a normal multimeter: DC V up to 1000V, AC up to 750V, resistance up to 40Mohm, frequency up to 10MHz, capacitance 100uF, AC/DC current 10A (and of course it has also a diode and continuity test). The measurement inaccuracy is overall around 1% according to documentation which is pretty acceptable figure.

The magic lies in the embedded oscilloscope functionality. When you need more than just multimeter reading, you can press a button and get oscilloscope view. In oscilloscope mode bandwidth for UT81B is 8MHz with 40MS/s giving resolution 100ns/div – 5s/div with 8bit ADC. You can do the oscilloscope measurements with normal multimeter leads (OK for low frequencies) or use adapter for real oscilloscope probe (for accurate measurement of higher frequencies).

ut81B1

Oscilloscope together with the multimeter is pretty ideal tool for the technician for reparations on the spot as well as for other professionals in workshops. Possibility to be powered by batteries turn this instrument in an ideal tool to be used as a mobile meter. LCD monochrome display with 160 x 160 pixels is very easy to read thanks to the back-light function.

The “Auto-Set” key allows to work very quickly and easily without too much trouble going through settings menus, although I must say that the automatic range setup is pretty slow (it can take more than 10 seconds for the meter to find appropriate vertical and horizontal range). Fortunately there is the manual mode so you can set the range and timebase yourself if you know in advance what to expect. Overall, for an 8MHz and 40MS/s scope the performance is very good.

Meter is best suited for measuring of larger continuous signals. You can stick it directly to mains power for example without worrying ab out anything. For very low level signals you can easily see interference on the measurements. Measuring on-off events on the scope screen is a bit hard also. One thing I noticed is that multimeter and oscilloscope seem to use pretty much separate electronics inside the device: multimeter part has pretty limited bandwidth while oscilloscope has high bandwidth. When you are working for example at 50 Hz mains power, scope and multimeter readings show about he same. But when measuring signals at many kHz frequency, scope still shows signal amplitude correctly, but multimeter reading shown on the screen is pretty much off from the right value. So multimeter voltage reading is just for DC and low frequency measurements.

When the whole device is battery powered, it is completely floating device, so you can freely measure circuit that are connected to ground or other potential that is not ground, just like any normal multimeter. When you power the device with batteries the multimeter is completely floating, and you are free to do all types of measurements without worrying any grounding issues (like with normal grounded oscilloscope). One good plus is that you can do oscilloscope measurements also on the current measurement range (measuring current waveforms with traditional scope would need some extra adapters / tricks).

The meter looks great and build quality is good. Case is plastic with a rubber surround. UT81B is quite a brick, a slightly big for a multimeter. The software running the device is not fast, neither too slow – acceptable, but could be faster.

The package includes opto-isolated USB cable, safety probes, safety banana to BNC converter, alligator clips, mains power supply, manual, CD with software for reading scope data, Uni-T 1 year warranty card and a zippered case.

Attached probes are OK, although crocodiles are quite big with lot of force. If you want to measure small components get other extra probes. There is some free space on the zippered case, so you can fit in some of your own probes. AC adapter option is a good plus, because batteries last only few hours of continuous measurement.

UT81B has optically isolated USB transfer cable. There is software that allows you to do measurements. Attached CD contains software for all UNI-T meters, but of course only for Windows. This software is not the best possible. I could not get the software that came with the device to work on my Windows Vista PC. I was lucky to find a newer version of the software for download, and after some hacking (running with administrator rights) I got it finally working. Not the most reliable or use friendly software, but works acceptably.

UT81B_OPROG

I found that lowlever blog UNI-T UT81B posting has description of UT81B protocol. This could be useful if you are planning to write your own software that communicates with this meter. The communication is serial port communications (9600 ,n ,8 ,1) over USB.

Other UT-81 reviews: Arc’s Lab Uni-Trend UT81B Review, lowlevel UNI-T UT81B review and TOOLBOOM Uni-T UT81B Oscilloscope Review.

Here are some UT81B presentation videos I found on YouTube:

12 Comments

  1. Shan Saches says:

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  3. Brenton Pettitt says:

    As a relative newbie to electronics testing I’ve purchased the Velleman EDU06 oscilloscope tutor kit, using the UT81B. Am I missing something in scope mode: I can’t see an RMS value displayed?

    Is the 40Mhz SCOPE PROBE & BNC worth investing in for greater accuracy? I can’t find it anywhere as an accessory!

    Thanks

    Reply
    • tomi says:

      I can agree that the the fact you can’t see RMS value displayed on the oscilloscope screen is a minus for UT81B.

      My UT81B came with BNC to banana adapters. I have used it to connect normal oscilloscope probe to this meter with it.
      Using oscilloscope probe compared to multimeter leads gives greater accuracy at higher frequencies (few MHz signals).
      At low frequency signal like mains voltage and audio frequencies practically the only benefit with real oscilloscope probe
      is just better shielding against external interference (shielded coaxial cable versus two unshielded wires).

      Reply
  4. Tomi Engdahl says:

    This is a nice introduction video:

    UNI-T UT81B Scopemeter and Arduino Teaser
    http://www.youtube.com/watch?v=UyfahKutJz0

    In this video I to a quick introduction to the UNI-T UT81b. I use it to demonstrate the PWM (pulse width modulated) signal being sent to an LED to fade it.

    Reply
  5. Tomi Engdahl says:

    Pocket Oscilloscope Review Roundup
    We put three miniature oscilloscopes to the test
    http://spectrum.ieee.org/geek-life/hands-on/pocket-oscilloscope-review-roundup/1

    Reply
  6. wael says:

    unfortunately i tried to measure the pwm signal of the smps that comes from pwm out pin to the gate of fet switch and the signal was narrow pulse and not square looking i wonder why i should be 100% square

    Reply
  7. Tomi Engdahl says:

    Custom software for interfacing via USB with multimeters UNI-T UT81B
    http://hmijailblog.blogspot.fi/2011/12/custom-software-for-interfacing-via-usb.html

    These multimeters are in fact pocket oscilloscopes. Quite an interesting package. And the possibility of interfacing via USB with a computer should multiply the possibilities.

    I jumped at the possibility of hacking the multimeter protocol and whipping up together our own program. And… it worked! From first idea to working product in 5 days, and having to learn Python and libUSB on the way!

    And not only that: our program bests the native one in that it has better precision (the native software averages every 2 samples), faster reaction times, and can read from an arbitrary number of multimeters in a single computer – even if the crappy interface cables all have the same USB PIDs and VIDs and serial numbers.

    First, capture and study the USB traffic between the multimeters and native software, using USBSnoop. Then, reverse engineer it

    UNI-T multimeters use a USB interface cable that is detected by Windows like a Human Interface Device (HID), so it uses a standard driver included with Windows.
    To use the multimeters with our own software, a special driver must be installed.
    At this point, the multimeter will no longer appear as a HID device, but as a LibUSB one

    The cable delivers continuously data, even if the multimeter is not connected.

    Reply
  8. Tomi Engdahl says:

    UNI-T UT81B Scopemeter Review
    https://www.youtube.com/watch?v=9SPcgNGTiOA

    Buyers guide and review of the UNI-T UT81B Scopemeter.

    Reply
  9. Timothy says:

    Hello.
    i am in possession of UT81B OSCILLOSCOPE. After some time of usage, i discovered after switching on, the screen get hanged with DETECT TEST- MODE glued to the screen. i have been trying to resolved this problem, but to no avail. please, what is your recommended solution ?

    Reply

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