01.02.2011|Articles

Uni-T UT81B Oscilloscope Review

Supermarket for engineers Toolboom offers universal measuring equipment UNI-T UT81B. It combines functions of full fledged multimeter and oscilloscope with analogue bandwidth up to 8 MHz. UNI-T brand is well known for its high accuracy and reliable measuring equipment. How did engineers manage to combine such complicated device as oscilloscope with multimeter in one case? What was the sacrifice for the sake of portability and what useful functions UNI-T UT81B possess?

Ergonomics of UNI-T UT81B Scope Multimeter

UNI-T UT81B scope multimeter is a device of medium dimensions and light weight. That is why it is easy to keep it in hand. Round knob is used to turn on power and shift mode of the multimeter. There are separate buttons for oscilloscope control and universal buttons for measuring device control in two modes. UNI-T UT81B device has small fault: some buttons are not enough touch sensitive. You need to heavily press them if you want to make them work. At the same time measurement mode switch of the multimeter works quite well.

UNI-T UT81B scope multimeter

There is support, section for batteries and socket for connection to personal computer on the backside of UNI-T UT81B scope multimeter. Small rubber feet in the bottom of the case help fixing measuring device when it is placed on the slippery surface.

Backside of UNI-T UT81B scope multimeter

Probes of UNI-T UT81B scope multimeter are used for two working modes of the measuring device.

Probes of UNI-T UT81B scope multimeter

You can connect alligator clips to UNI-T UT81B probes, and it would be more comfortable for you to hold on pins on the electric schemes. They are equipped with rubber insulating jackets. It allows you to connect probes to alive terminals.

Alligator clips of UNI-T UT81B scope multimeter

UNI-T UT81B Scope Multimeter Control Menu

Control of handheld oscilloscope which also has functions of the multimeter significantly differs from control of the fixed device. First of all, there are less buttons on the control panels and menu is much more user friendly. However, you need to get used to control even of such simple device. There is no Russian version of menu of UNI-T UT81B scope multimeter.

There are special buttons on the control panel for oscilloscope control and general buttons for oscilloscope and multimeter control. You can switch between multimeter functions with the aid of round knob. MODE button is used for switching between two modes of measuring device.

UNI-T UT81B scope multimeter control panel

You can set type of the measured parameter with the aid of the switch:

  • voltage
  • resistance, circuit continuity check, diode test
  • frequency
  • current
  • capacitance

F1 button is meant for selection of the type of current and voltage to be measured (direct or alternate), and also circuit continuity check and diode test mode. Measuring range selection can be both manual and automatic.

In voltage and currency measuring mode you can select type of voltage/currency (AC/DC), set mode of relative measurements (REL), manually set measuring range (RANGE).

In resistance measuring mode you can select relative measurements mode and measuring range. You can also select mode of diode test or circuit continuity check.

When measuring signal frequency you can turn on mode of duty factor.

And finally capacitance measuring function provides only relative measurements mode.

Oscilloscope function is active during voltage, frequency and current measurement. Wave form scale can be set manually or automatically by AUTO button. In order to change amplitude scale use F3 and F4 (RANGE) buttons, and F1 and F2 (MOVE) buttons are meant for positioning on the display. In order to change time scale and horizontal movement of oscillogram you need to move to TIME mode and by F1, F2, F3 and F4 buttons, signed on the BASE screen, set the necessary parameters. You can distinguish automatic scale setting from the manual in the following way: In manual mode voltage or time parameter is displayed by black symbols on the white background. In automatic mode situation is quite the opposite.

Oscilloscope mode of UNI-T UT81B measuring equipment

Trigger is an important option of oscilloscope. This mode allows triggering signal according to the certain level of rising or falling edge. There are three trigger modes: automatic, normal and single.

Mode of saving oscillograms allows storing 10 wave forms into UNI-T UT81B scope multimeter memory, and subsequently display them on the screen. You cannot zoom saved signal, the only operation you can perform with it is movement along the time base.

Settings mode of the UNI-T UT81B measuring device (SET) allows adjusting function of automatic shutdown of power, sound signal during circuit continuity check and display parameters.

  1. Auto Off - setting time of automatic shutdown of power within the range from 1 to 31 minutes.
  2. BK Light - display brightness adjustment function. The level varies within the range from 1 to 31. After device shutdown this parameter is not saved.
  3. Contrast - adjustment of display contrast ratio. Contrast ratio adjustment in relative units from 1 to 31. This parameters is also not saved after the device shutdown.
  4. BEEP - option of turning on and off of the sound signal during the circuit continuity check. After power is shut down settings are not saved.

Display of UNI-T UT81B Scope Multimeter

Display of UNI-T UT81B scope multimeter should be large enough for oscillogram display. In multimeter mode monochrome screen displays big figures which are quite visible in daylight and in dark places. Backlight is almost unnoticeable in a daylight and is perfectly visible in conditions of dim illumination.

Multimeter mode of UNI-T UT81B measuring equipment

Software of UNI-T UT81B Scope Multimeter

UNI-T UT81B digital scope multimeter can be connected to personal computer. USB cable with optical coupler is used for connection.

Connection USB cable of UNI-T UT81B scope multimeter

Program for UNI-T UT81B oscilloscope multimeter is easily installed on the computer. It allows registering readings of all measured units in the form of the table. Oscillograms are displayed in graphics format.

Software of UNI-T UT81B scope multimeter (multimeter mode)

Oscilloscope measurements display:

Software of UNI-T UT81B scope multimeter (oscilloscope mode)

The data are stored in the form of the table:

Storing data of UNI-T UT81B scope multimeter measurements (in the dorm of the table)

Oscillogram picture is saved in bmp. format:

Storing oscillogram taken by UNI-T UT81B scope multimeter in bmp. file

Interval between measurements can be set from 1 second up to several hours, you can also skip values repeated in sequence which allows you to significantly shorten the table.Number of measuring points is set from 1000 up to infinity. The program sets interval of 0.2 seconds between measurements by default.

Although software to UNI-T UT81B scope multimeter is quite easy it helps following changes in the parameters of electric mains and electric circuits.

Technical Capabilities of UNI-T UT81B Scope Multimeter

We decided to hold small test of UNI-T UT81B scope multimeter and check its real capabilities. Using RIGOL DG2041A waveform generator was the only possibility to give oscilloscope a run in the whole range of working frequencies. We fed signals of various forms and frequencies to the input of UNI-T UT81B scope multimeter. That is what we've got:

Let's start from the square wave (meander). The pictures display only relative scale of the amplitude. It is connected with the peculiarity of software of UNI-T UT81B scope multimeter with the aid of which we made screen shots. The pictures display the difference of wave forms on the various frequencies:

Signal frequency is 10 kHz, set amplitude - 2.5 V. Signal amplitude does not decrease during measuring.

Meander is taken by UNI-T UT81B oscilloscope

Signal frequency is 100 kHz, set amplitude - 2.5 V. Signal amplitude does not decrease during measuring.

Meander is taken by UNI-T UT81B oscilloscope

Signal frequency is 400 kHz, set amplitude - 2.5 V. Signal amplitude does not decrease during measuring.

Meander is taken by UNI-T UT81B oscilloscope

Signal frequency is 1 MHz, set amplitude - 2.5 V. Amplitude decreased during measurement to 2.3 V.

Meander is taken by UNI-T UT81B oscilloscope

Signal frequency is 5 MHz, set amplitude - 2.5 V. Amplitude decreased during measurement to 2.1 V.

Meander is taken by UNI-T UT81B oscilloscope

Signal frequency is 8 MHz, set amplitude is 2.5 V.

Meander is taken by UNI-T UT81B oscilloscope

Meander amplitude on the frequency of 8 MHz decreases to 1.4 V. You can also see what is happening to its shape. Lets show the same meander taken by Rigol DS1102E digital oscilloscope with the aid of coaxial cable. Signal frequency is 8 MHz, amplitude is 2.5 V.

Meander is taken by Rigol DS1102E oscilloscope

The shape remains more or less square, and the amplitude decreases approximately by 0.3 V.

Sawtooth waveform. Signal frequency is 400 kHz, set amplitude is 2.5 V.

Sawtooth waveform is taken by UNI-T UT81B oscilloscope

Signal amplitude decreases during measuring to 2 V, but the shape is well preserved.

Sine shaped waveform.

Signal frequency is 500 kHz, set amplitude is 2.5 V. Amplitude shown by the oscilloscope is approximately 2 V.

Sine shape waveform is taken by UNI-T UT81B oscilloscope

Amplitude decreases to 1 V at 8 MHz frequency.

Sine shape waveform is taken by UNI-T UT81B oscilloscope

This test showed that using common probes of the multimeter leads to incorrect work of the oscilloscope. The signal (specially meander) shape is distorted on the high frequencies. Once we had problems with application of ordinary oscilloscope probes when working with generator. Waveform was significantly distorted and lost its amplitude. Only application of coaxial cable allowed us to obtain good data. We faced the same problem with UNI-T UT81B scope multimeter. This problem can be solved by application of special adapters of oscilloscope probes (not included in the package).

Technical Specifications of UNI-T UT81B Scope Multimeter

Display (LCD) Monochrome, 3999 digit, refreshment 2-3 times/s
Working environment temperature from 0ºC - to 40 ºC
Storage temperature from -10 to + 50 ºC
Relative humidity ≤ 75% at temperature from 0ºC to 40 ºC
Power source 1.5 V (R6) × 4 batteries or power supply unit
Dimensions 200 × 100 × 50
Weight 500 g (with batteries)

Technical Specifications of UNI-T UT81B Multimeter

Parameter Measuring range (accuracy) Overload protection
DC voltage 400 mV/4/40/400 V ±(0.8%+8)
1000 V ±(1.0%+8)
1000 V
AC voltage 4/40/400 V ±(1.0%+15)
1000 V ±(1.2%+15)
1000 V
DC current 400/4000 mkA ±(1.0%+8)
40/400 mA ±(1.2%+8)
4/10 A ±(1.5%+8)
fuse 0.5 A/250 V, d5×20 mm
fuse 10 A/250 V, d5×20 mm
(Measuring time up to 10 seconds, interval
between measurements - 15 minutes)
AC current 400/4000 mkA ±(1.5%+8)
40/400 mA ±(2.0%+8)
4/10 A ±(2.5%+5)
fuse 0.5 A/250 V, d5×20 mm
fuse 10 A/250 V, d5×20 mm
(Measuring time up to 10 seconds, interval
between measurements - 15 minutes)
Resistance 400 Ohm ±(1.2%+5)
4/40/400 kOhm ±(1.0%+5)
4 MOhm ±(1.2%+5)
40 MOhm ±(1.5%+5)
250 V DC or AC rms
Frequency 10 Hz - 10 MHz ±(0.1%+3) 250 V DC or AC rms
Amplitude of input signal:
from 300 mV to 30 Vrms for frequency ≤1 MHz
from 600 mV to 5 Vrms for frequency > 1 MHz
Pulse ratio 0.1%-99.9% 250 V DC or AC rms
Capacitance 40 nF ±(3.0%+10)
400 nF/4 mkF ±(3.0%+8)
40 mkF/100 mkF ±(4.0%+8)
250 V DC or AC rms
Diodes test 250 V DC or AC
Continuity test 250 V DC or AC
Sound signal at resistance ≤ 100 Ohm

Technical Specifications of UNI-T UT81B Oscilloscope

Horizontal System
Sampling rate 40 MHz
Sampling rate / scale 20 pixels
Refresh rate >5
Trigger modes Auto, Normal, Single
Horizontal System 100 ns/div - 5 s/div. (1-2-5)
Horizontal system accuracy ±(0.1%+1 pixel)
Vertical system
Analogue bandwidth 8 MHz
Channels number 1
Input coupling Direct component (DC)
Vertical resolution 8 bit
Accuracy ±(5.0%+1 pixel)
Maximum input voltage 1000 V (maximum amplitude)
Voltage response 200 mV/div – 500 V/div

Package Content of UNI-T UT81B Scope Multimeter

  1. UNI-T UT81B digital scope multimeter
  2. 6 V power adapter
  3. Measuring probes
  4. Removable crocodile clips
  5. USB cable for computer connection
  6. Batteries
  7. CD with software
  8. User manual
Package content of UNI-T UT81B scope multimeter

All parts are packed into case:

Case of UNI-T UT81B scope multimeter

Package of UNI-T UT81B scope multimeter is quite bright. It's a good choice for the gift.

Package of UNI-T UT81B scope multimeter

Conclusion

We described basic functions of UNI-T UT81B scope multimeter. First of all it's a full fledged multimeter with wide measuring range of electric values. This device lacks a lot of useful options of full fledged oscilloscopes, however, UNI-T UT81B is good enough for simple tasks of detecting faults in electric and electronic circuits and also their adjustment. It's quite enough for working with signals up to 8 MHz.

Simple software of UNI-T UT81B measuring equipment allows registering measurements in easy format and further analysis of the obtained data.

You can adjust brightness and contrast ratio of the display, set time of automatic power shutdown in the settings menu.

Sergiy Safonyuk
ToolBoom technical specialist

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