UNI-T UT139 True RMS Digital Multimeters

Overview

UT139A/B/C DMM is a small auto range, hand-held 3 1/2—3 5/6 bit true RMS multimeter featuring complete function, novel structure, high reliability and safety as well as large screen for display . It can be used for measuring ACIDC voltage and current, variable frequency voltage (V.F.C), resistance, diode, circuit on-off, capacitance, frequency ratio, NCV non-contact AC voltage sensing and so on, is an ideal portable maintenance instrument for users.

Accessory

Unpack and take out the instrument, please check following attachments carefully for completeness or intactness.
In case of any shortage or damage, please contact with your supplier

1. An operating instruction manual
2. A test pen (CAT 111 600V)10A
3. Point-type K( nickel chromium nickel silicon) thermocouple (UT139C only)
4. An optional current clamp (UTI 39C only)

Safety Information

IJT139A/B/C is designed in compliance with standards such as IEC/EN61010-1, pollution grade 11, overvoltage
(CAT111600V) and double insulation standards. Please comply with operation instructions specified in the Manual; otherwise the protection provided by the instrument may be affected.
CE:This Meter complies with the standards EN 61010-1 ,EN 61010-2-030: in pollution degree 2, overvoltage category (CAT Ill 600V) and double insulation.

ETL/cETL: CONFORMS TO UL STD 61010-1, 61010-2-030
CERTIFIED TO CSA STD C22.2 No. 61010-1, 61010-2-030

1. It is forbidden to use the product without having rear cap in place, or othenuise there will be electric shocking.
2. Prior to use, inspect the insulation layer of test pen for intactness, confirming no breakage and broken line.
3. When LCD display shows the icon ” it is required to replace the battery in time to ensure the measurement accuracy.
4. Range switch shall be set at the correct measurement position.
5. In case of electric shock and damage to the instrument, signals being measured shall not exceed rated limit value.
6. To prevent any damage to the instrument, it is forbidden to change the gear of range switch in measurement.
7. After each measurement, disconnect table pen and the circuit being measured; after the current measurement, especially the measurement of large current, it is necessary to power off before disconnecting table pen and the circuit being measured.
8. In case of electric shock, it is required to be cautious when voltage being measured higher than DC 60V or AC 30Vrms.
9. Do not use the product in high-temperature or high-humidity environment, particularly in the damp environment in where the instrument performance may be severely degraded
10. Refrain from changing the internal wiring in the clamp ammeter to guard against damage to the meter and danger.
11. Clean the meter case with damp cloth and mild detergent rather than the abrasive material and solvent.

Electric Symbol

Comprehensive Specification

1. Maximum voltage between input tenninal and grounding: see instruction about each input tenninal protection voltage.
2. 10A terminal (CE) is equipped with:
   F 10A H 600V fast-acting fuse (<l>6×25) mm
3. mNµA terminal (CE) is equipped with:
   • UT139A-FF 0.2A H 600V fast-acting fuse (<l>6×32) mm
   • UT139B-FF 0.5A H 600V fast-acting fuse (<l>6×32) mm
   • UT139C-FF 0.6A H 600V fast-acting fuse (<l>6×32) mm
4. Maximum display: (UT139A): 1999; (UT139B): 4000; (UT139C): 6000Refresh 2~3 times per second, display “OL” in case of overrange .
   • Capacitance and frequency (only applicable for UT139B/C): 9999 count.
   • Duty ratio (only applicable for UT139B/C): 1~99.9%
   • Diode: about 2.1V (UT139A) and 3.2V(UT139B/C), displaying “OL” in case of overrange.
   • Range: auto/manual
   • Polarity: auto
   • Working temperature: o·c~40’C
   • Relative humidity: ?75% when o·c~30’C, and ?50% when 30’C~40’C
   • Storage temperature: -10’C~50’C
5. Electromagnetic compatibility:
   In 1V/m radio frequency (RF) field: Overall accuracy=specified accuracy+ 5% of range, and no specified index for RF over 1V/m.
6.  Operating ASL: 0~2000m
7.  Internal battery: AA R6P 1.5Vx2
8. Low electricity: LCD displays””.
9. Contour dimension: about (175x80x48.5) mm
10. Weight: about 350g (inclusive of battery)
11. Safety Standard: IEC/EN 61010-1: CATIII600V; Pollution grade II
12. Accreditation: CE

Appearance Structure (See Figure 1)

1. Case
2. LCD Display
3. 4/
4. 7.: Selection buttons
5. Range Switch
6. Measuring input terminal

LCD Display (See Figure 2)

Knobs and Keys for Range selection

Button
RANGE button: it can be used for selecting auto/manual range. After pressing, it will switch one gear of switch, when reading the highest gear, jump to the lowest gear range and in turn. When the time of pressing button is or switching a range, you’ll exit the manual range mode. (Only applicable for V&/Q/Iæ )

MAXIMIN button:
it can be used to automatically enter the manual range mode. In such case, auto shutdown function is disabled and maximum value is displayed, after another pressing on the button, the minimum value will be displayed and values are displayed in turn (maximum value-minimum value). When the time of pressing button is or switching a range, you’ll exit data recording mode (only applicable for væ, Q, IQ and C/ OF)

REL button
it can be used to automatically enter the manual range mode. The current displayed value will be taken as the reference value and then the difference bebween the measured value and reference value will be displayed, after another press, you’ll exit the relative measurement mode. (Only applicable for Q, 1>4, C/T and-1€)
The backlight will be illuminated when the time of pressing button is >2s, after about 15s, the backlight will be automatically turned off; the backlight will be turned off if pressing the key when the backlight is illuminated, (Only applicable for IJT139A full range: REL/LIGHT button)
NCV/rnV’+u button (Only applicable for UT139A):
It can be used to switch NCV/rnV•-u. For detailed information, see the operation instruction for non-contact

AC voltage sensing.
Hz/% button (only applicable for UT139B/C):
It can be used to select the mode Hz/%, only applicable for the selection of frequency, AC voltage/ current measurement modes,

SELECT button
it can be used to select range (only applicable for multi-range). Under AC mode. press the button >2s, display “IJFC”, enter V.F.C measurement mode and measure the variable frequency voltage. After another
pressing on the button, display “End” and exit the V.F.C measurement mode.

HOLD button: (Applicable for full range) after another
It can be used to lock and hold the displayed value, in such case, LCD displays the prompt ” press, it is unlocked and enter the normal measurement mode.
The backlight will be illuminated when the time of pressing button is >2s. after about 15s, the backlight will be automatically turned off; and the backlight will be turned off if pressing the key when the backlight is illuminated, (Only applicable for UT139A full range: HOLD /LIGHT button)

Measurement Instruction

Check battery in the time. built-in It is AA required 1.5Vx2 to battery, pay dispattention lay will to the show symbol the symbol “beside when the test lack of pen power, socket, and which then reminds replace
one of the fact that in case of measurement safty, testing voltage or current shall not exceed the specified value

1. AC and DC Voltage Measurement (See Figure 3)
   1. Connect the instrument with the load in parallel for measurement.
   2. When the input impedance of the instrument is about 10M Q, the load may cause measurement error in the circuit with highimpedance. In most cases, the error can be neglected (0.1 % or lower) if the circuit impedance is under 1 Ok

Notes:

• It is forbidden to input voltage higher than 600Vrms, despite  of  possibility of measuring higher voltage, as it may damage the instrument.
• It is required to avoid the electric shock in measuring high voltage.

Resistance Measurement (See Figure 4a)
Connect the instrument with the load in parallel for measurement.

Notes

• The display will show “OL” when the measured resistance open-circuit or resistance value exceeds the maximum range of the instrument.
• Proffer all to powers measuring in the online circuits to resistance, be ii measured, is necessary and to release switch all residual charges to ensure the measurement accuracy.
• In measuring low resistance, a measurement error in resistance of about 0.1 Q ~0.2 Q will be resulted by the test pen. In order to acquire accurate reading, it is required to short circuit the test pen, take REL relative measurement mode to ensure the measurement accuracy.
• Check the test pen for any loosening or other reasons in case there is a resistance value no less than 0. 50 when test pen is short circuited.
• Several seconds may be required for the reading stability when measuring high resistance, which is normal for high resistance measurement.
• By using the resistance measurement function, it is allowed  to make self-checking of the built-in fuse, see (Figure 4b).
• No input higher than DC 60V or AC 30V is allowed.

Circuit on-off measurement (See Figure 5)

If 150 the resistance of two terminals to be measured is bigger good sound; Q, if there the conductivity will resistance be and a buzzer is circuit  the and continuously circuit buzzer is sound. will deemed make.
If the of terminals to be measured is bigger than 150 Q, there will be a circuit break and buzzer will make no sound; if the resistance is  the circuit is  with good conduct and will sound.

Notes
Prior b online circuit on-off, it is b switch off all power supplies in the circuits to be measured and release all residual charges to ensure the measurement accuracy.
* To prevent personal injury, it is not allowed to input the higher than DC 60V or AC 30V.

Diode measurement (Figure 6)

“OLO will be displayed when the to be measured is an open circuit or polarity is reversely connected. For Silicon PN junction, the normal value is normally

Notes
Prior to measuring online it is necessary to o switch off all power supplies in the circuits to be measured and release all residual charges to ensure the accuracy.

Test voltage for diode is about:

(UT139A),
(UT139B/C).
* To prevent personal injury, it is not allowed to input the voltage higher than DC 60V or AC 30V

Capacitance measurement (Only applicable for UT139B/C)

(See Figure 7) The instrument, when without any input, will value. display a When fixed reading measuring which small is the range internal gear fixed , the  to above ensure value the to shall accuracy. be automatically relative subtract from the the measurement value value to to be REL facilitate measured function the can be measurement.

Notes
* The short-circuited display will or show the “OL” capacitance when the value capacitor exceeds to the be maximum becomes.

Notes
The display will show “OL” when the capacitor to be becomes short-circuited or the capacitance value exceeds the maximum range of the instrument.
Generally, several seconds will be taken to measure high-capacity capacitor.
To prevent damage to the instrument and personal injury, it is required before testing to release all residual charges, which is particularly important for capacitor with high voltage.

Frequency/Duty Ratio Measurement

(Only applicable (See Figure 8) At the frequency measurement gear, press the button Hz/% to select frequency/duty ratio measurement mode.

Notes
To prevent personal injury, it is not allowed to input the voltage higher than DC 60V or AC 30V

Temperature measurement (Only applicable for UT139C)

(See Figure 9) Temperature sensor: It is only applicable for K  (Ni-Cr and Ni- Si) thermocouple. After startup, “OL” is displayed,  complete Celsius or Fahrenheit temperature measurement by  connecting the product with K-type temperature sensor.

Notes
The point type K (Ni-Cr and Ni- Si) thermocouple is only applicable for the measurement of temperature under 2300C/4460F.

AC and DC current measurement (See Figure 10)

Connect the instrument with the load in serial for measurement.
AC measurement value will be true RMS.

Notes

• Before connecting instrument in serial with the loop to be measured, switch off the power supply.
• In measurement, it is required to use proper input terminal and function gear; if unable to estimate the current, the measurement should start with the high area range.
• Fuses are provided inside the IOA, mA7u input jacks. It is forbidden to connect the table pen test pin in parallel with any circuit, especially from power supply terminal, which may cause damage to the Instrument and personal injury.
• For security purposes, when measuring current higher than 5A, the time of each measurement should be controlled less than IOS and an interval of at least 15min should be maintained.
• When measuring AC current online, it is allowed to press button Hz/% to display online AC frequency/ duty ratio.
• 60AAC and DC current clamp measurement (See Figure 11).
• Connect as shown in the re with the attached current clamp.
• (Only applicable for UTI

NCV Non-contact AC voltage sensing (See Figure 12)
If need to detect whether there is a AC voltage or electromagnetic field, allow the front end of the instrument be close to the object to be sensed. The analog quantity of sensed AC voltage is about: “EF” is displayed when critical voltage.
“EF” is displayed when UT139A> critical voltage, a five-level sound effect (buzzing sound) is generated according to the voltage Vd to mark the difference of sensed voltage.
“-” is displayed when UT139B/C>critical voltage,”- – – -” is designed according to the size of voltage Vd and accompanied by different buzzing sounds to mark the difference of sensed voltage.
By pressing NCV/mV”-‘(only applicable for UT139A), display the analog quantity of sensed mV”-‘to make the difference of AC voltage .

Notes
Test pen is not required for measurement when the range knob switch is set at “NCV”.

Battery voltage measurement (only applicable for UT139A)

(See Figure 13) The range gear 1.5V is only applicable for the measurement of battery 2v, with load resistance of about 51 Q, while the range gear 9V is only applicable for the measurement of a battery with load resistance.

To prevent the built-in fuse F1 inside the instrument from burning out due to overload, it is forbidden to measure the battery or power supply beyond the rated range.
The measuring time for battery voltage should be as short as possible since there will be built-in analog load power consumption which may shorten the service life of battery.

Other functions

• After 2s of full display following startup, the normal measurement mode. “ErrE” will be displayed in case of any fault to the internal EEPROM.
• Auto power-off: the instrument will be “automatically powered off’ to save energy in case of no operation to the knob switch within 15min. Under auto power-off status, any press on the SELECT of UTI 39A or any button of UT 139B/C will “automatically arouse” the instrument, or restart the instrument by turning the knob switch to OFF. Under power-off status, press on SELECT and power on, the buzzer will make five sounds to remind that the auto power-off function has been cancelled. Restarting the instrument after power-off will
  recover the auto power-off function.
• Buzzer: A “Beep” sound (about 0.25s) from buzzer means the function button is valid when pressing any button or turning the function button. When measuring voltage or current: AC and DC voltage > about 600V mA gear AC/DC current 390mA(UT139B), A gear AC/DC current is IOA, buzzer will make continuous sounds to remain the over-range. In addition, the buzzer make make 5 continuous sounds about 1 min prior to auto power-off and then make a long sound prior to power-off.
  When the auto power-off function is cancelled, 5 sounds will be made by the buzzer every 15min.
• Low-voltage detection: it is used to detect the internal VDD. When the voltage is lower than 2.4V, the battery under-voltage symbol “” will be displayed, and the normal operation is available; while when lower than 2.2V, no is allowed and only the symbol is displayed after startup.
• When the battery supply voltage is reduced to 2.6V, the LCD backlight is weak or can not start; measurement functions can still be used normally.

Technical Index

Accuracy: ± (a% reading +b word number), one year of guarantee period.
Ambient temperature: 230 (73.40F {-9 T’ ) Relative humidity: <75%.

1. DC voltage measurement

OMO. (There will be unstable digital display in case of * /** range circuit after connecting with the load, it can be controlled s ±1)

• Range: 20mV range for UT139A, 40mV range for UT139B, 60mV range for UT139C.
• Range : 200mV range for UT139A 400mV range for UT139B 600mV range for UT139C.
• Maximum input voltage: ±600V

AC voltage measurement

Input impedance: about IOMQ.
Display the true RMS. Frequency response: IJT139A 45—400Hz, UTI 39B/C 45—1 kHz.(VFC: 45—400Hz)
Assurance of accuracy:5—100% range, an allowance of <10 words of residual reading for short-circuit.
It will be up to 3.0 when AC crest factor reaches full value (with except for 600V range, which is up to 1.5 when the range reaches the full value). Maximum input voltage: 600Vrms

Resistance measurement

Range: measured value = displayed value — short-circuit value of test pen.
Open-circuit: about *IV
*. Overload protection: 600V-PTC

Circuit on-off, diode measurement

Overload protection: 600V-PTC

Capacitance Measurement (Only applicable for UTI 39B/C)
A Overload protection: 600V-PTC
For capacitor < 1 pF, it is recommended to adopt REL measurement mode to ensure measurement accuracy.

Frequency/duty ratio measurement (only applicable for UTI 39B/C)

• Over-load protection: 600V-PTC
• Input range a: (DC level is zero) > 1 MHz : 5MHz—10MHz
• Duty ratio %: only applicable for measurement < 100kHz

Remark.

• During measurement of AC voltage or AC current, if need to read online frequency value or duty ratio, following input should be met: frequency response: < 1 kHz;
• SAC voltage: mV range input > 100mV; V range input > range x60/o
• AC current: input range a 4000/6000pAj 400/600mA, IOA range: range *60/0 400/600pA, 40/60mA, 4/6A range: range x600/0

Temperature measurement (only applicable for UTI 39C)

Over-load protection: 600V-PTC
Remark: The point type K (Ni-Cr and Ni- Si) thermocouple is only applicable for the measurement of temperature under 230 C/4460F

DC current measurement

Over-load protection

• A range:
• Fl fuse: FFO.2AH 600\./ (CE) UT139A FFO.5A H 600V (CE) UT139B FFO.6A H 600V (CE) IJT139C 10 A range: F2 fuse: @6×25)mm
• F IOA H 600V (CE)

AC current measurement

• Frequency response: UT139A 45—400Hz, UT139B/C 45—1 kHz
• Display: true RMS.
• Assurance of accuracy: range, an allowance of <2 words of residual reading for short-circuit.
• It will be up to 3.0 when AC crest factor reaches full value.
• A Over-load protection: (the same as the DC current over-load protection)

 current clamp measurement (only applicable for UT139C) Batter capacity measurement (only applicable for UTI 39A)

Over-load protection: Fl fuse: (Q6x32)mm FFO.2A H 600V (CE)

Upkeep and Maintenance

Warning: Power shall be switched off before opening the rear cover of the instrument and the test pen shall be away from the input terminal and circuit to be measured.

1. Conventional upkeep and maintenance
   For upkeep and maintenance, wet cloth and mild cleanser rather than abrasive or solution shall be used to clean the meter housing.
   • Please stop using and send for maintenance in case of any abnormal condition about the instrument.
   • The inspection or maintenance for instrument, if necessary, shall be performed by the qualified professional maintenance personnel or designated maintenance department.
2. Battery or fuse tube replacement (See Figure 14)
   Built-in battery shall be replaced in time when LCD displays the under-voltage prompt” otherwise measurement accuracy may be affected.

Battery specification: AA 1.5Vx2

Operating steps:

1. Set the power switch at “Off” take the test pen away from the input jack and remove the protective sleeve .
2. Screw off one screw securing batter rear cover with screw driver, remove the cover and replace:
   • The under-voltage used battery and burnout fuse:
   • F1 fuse: Ccp6x32) mm FF0.2A H 600V (CE)(UT139A)
   • FF0.5A H 600V (CE)(UT139B)
   • FF0.6A H 600V (CE) (UT139C)
3. Screw off the second screw securing the rear cover with screw driver and remove the cover to replace the burnout F2 fuse Ccp6x25) mm F 10A H 600V (CE).

Documents / Resources

UNI-T UT139 True RMS Digital Multimeters [pdf] Instruction Manual UT139 True RMS Digital Multimeters, UT139, True RMS Digital Multimeters, Digital Multimeters, Multimeters

References

• User Manual