UNI-T UT18A/B/C/D/E Voltage and Continuity Tester Operating Manual

1. Symbols Referred in the Manual

The manual includes necessary information regarding the safe usage and equipment maintenance. Before use, read through each section of the manual. Failure to read the manual or comprehend the equipment use method specified in the manual would lead to physical injury and equipment damage.

• ⚡ Dangerous Voltage: Please refer to instruction sheets.
• ? Important Information: Please refer to instruction sheets.
• ⛋ Double Insulation: Suitable for living and working.
• ♻️ Waste Disposal: Do not discard the product as unclassified municipal waste. Put them in the designated battery recycle bin for further disposal.

EU Certification: Conforms to UL STD 61010-1, 61010-2-030, 61010-2-033, 61010-031, Certified to CSA STD C22.2 No. 61010-1, 61010-2-030, 61010-2-033, 61010-031.

Measurement Category III: Applicable to test and measuring circuits connected to the distribution part of the building's low-voltage MAINS installation.

Measurement Category IV: Applicable to test and measuring circuits connected at the source of the building's low-voltage MAINS installation.

Symbol on Tester Panel and Its Description (Figure 1)

Figure 1 Description: This figure illustrates the various components and indicators on the tester panel.

• 1: Test pen L1
• 2: Test pen L2
• 3: Voltage indication (LED)
• 4: LCD display
• 5: High-voltage indication (LED)
• 6: AC indication (LED)
• 7: Continuity indication (LED)
• 8: Polar indication (LED)
• 9: Rotary phase indication (LED)
• 10: RCD indication (LED)
• 11: RCD test button
• 12: Flashlight/self-inspection button
• 13: HOLD mode/backlight button
• 14: Flashlight
• 15: Test pen cap
• 16: Battery cover

Figure 2 Provides Detailed Description of LCD Panel

Figure 2 Description: This figure shows the indicators on the LCD panel.

• 1: Silent mode indication
• 2: HOLD mode indication
• 3: Low-voltage battery indication
• 4: Voltage measurement
• 5: Frequency measurement
• 6: DC voltage measurement
• 7: AC voltage measurement
• 8: Voltage indication (LCD segment code)
• 9: High-voltage indication
• 10: Continuity indication
• 11: RCD indication
• 12: Rotary phase indication

(Visual representation of LCD panel with various indicators like 690V, 400V, 120V, 24V, 12V, 6V, RCD, AL, VAG, VDG, Hz, HOLD, Silent mode indicators, etc.)

2. Operation Instruction and Use Scope of the Tester

The voltage and continuity tester includes four models: UT18A, UT18B, UT18C, UT18D, and UT18E. It offers functions such as AC/DC voltage measurement (including three-phase alternating current), three-phase AC phase indication, frequency measurement, RCD test, continuity test, simple test without battery power, self-inspection, silent mode selection, overvoltage indication, and low-voltage battery indication. The integrated flashlight provides convenience in dark environments. The tester is equipped with a protective jacket for safety and durability. It is suitable for household, factory, and electric power department applications.

Key Characteristics:

• Protective jacket for physical injury prevention.
• LED indication (UT18A/B/C/E).
• LCD voltage and frequency display (UT18C/D/E).
• AC/DC measurement up to 690V; UT18E reaches 1000V.
• Continuity measurement.
• Indicates phase relationships among three-phase AC.
• Optional buzzing and silent modes.
• Detection without battery (UT18A/B/C/E).
• Flashlight function.
• Self-inspection function.
• Low-battery voltage indication and measured voltage over-range indication (UT18E requires battery replacement when low).
• RCD test (UT18B/C/D/E).
• Automatic standby.

3. Safety Precautions

To prevent physical injury, electric shock, or fire, pay special attention to the following items:

• Before using a voltage detector with an audible indicator in locations with high background noise, ensure the audible signal is perceptible.
• Voltage detectors are designed for use by skilled persons following safe work methods. The indicating signals (including ELV limit indication) are not for measuring purposes.
• Ensure both the test pen and test instrument are intact before testing.
• Keep hands only in contact with the handle while using the equipment.
• Never use the equipment when the voltage is beyond the specified range (refer to technical specifications) or above 800V.
• Before use, ensure the equipment functions correctly. For normal operation, measure a known voltage value first.
• The tester is unusable if one or several functional failures occur or if there is no functional indication.
• Never test in wet conditions.
• Display functions correctly only within temperature ranges of -15°C to +45°C and relative humidity below 85%.
• The instrument must be repaired if the personal safety of the operator cannot be guaranteed.

Safety is no longer guaranteed in the following circumstances:

1. Visible damage.
2. Tester's functions are inconsistent with its intended purpose.
3. Stored in inappropriate conditions for a long time.
4. Subject to mechanical extrusion during transit.

4. Voltage Measurement

Observe safety test regulations specified in item 3.

The voltage gear of the tester uses LED or LCD segment codes for indication, covering ranges from 6V (UT18D) up to 690V, and 1000V for UT18E. Indicators light up sequentially with increasing voltage, along with polarity, AC, continuity, RCD, rotary phase, and high-voltage indications.

1. Self-Check: Before testing, press the flashlight key for 5 seconds. The tester performs AC/DC full-range detection with flashing LEDs (except RCD light) and blinking LCD. Touch the flashlight key to exit self-check. Connect test pens to the conductor, select a known voltage (e.g., 220V socket) for measurement accuracy (See Figure 3). The tester cannot measure AC/DC voltage below 5V and provides no accurate indication for 5Vac/dc. Illuminating continuity light, AC light, or high-voltage symbol (UT18D) and beeping buzzer are normal.
2. Indication Types: UT18A/B use LED indication; UT18C/E use LED+LCD; UT18D uses LCD. A high-voltage LED illuminates and a buzzer beeps at the extra low voltage (ELV) threshold. If the measured voltage exceeds the tester's input protection voltage (UT18A/B/C/D: 750Vac/dc, UT18E: 1015Vac/dc), the corresponding LED flashes (UT18A/B/C/E), the LCD displays "OL" (UT18C/D/E), and the buzzer beeps continuously.
3. DC Voltage Measurement: Connect L2 to the positive pole and L1 to the negative pole of the object. The LED indicates the corresponding voltage, and the LCD displays the voltage. The positive pole LED illuminates, and the LCD displays "+" "VDC". If connected in reverse, the negative pole LED illuminates, and the LCD displays "-" "VDC". To determine polarity, connect test pens randomly; the illuminating positive pole LED or LCD "+" indicates the positive terminal connected to L2.
4. AC Voltage Measurement: Connect test pens randomly to the object. The AC LED illuminates ("+", "-" LEDs illuminate simultaneously for UT18E). The LCD displays "VAC", and LEDs indicate the corresponding voltage value.

Note on AC Voltage: For AC voltage measurement, L and R phase inversion indication LEDs (UT18A/B/C/E) or L and R symbols (UT18D) may illuminate, indicating unstable phase indication. L or R light may illuminate individually, or L and R lights may illuminate alternatively. Correct and stable indication of L and R requires measuring a three-phase power system.

Figure 3 Description: This figure illustrates an example of voltage measurement on an LCD panel, showing indicators like 690V, 400V, 120V, 24V, 12V, 6V, RCD, AL, VAG, VDG, Hz, HOLD, and silent mode.

5. Detection Without Battery

The tester can perform simple detection even when the battery is low or absent. Connect the two test pens to the object. If the object has a voltage higher than or equivalent to 50V AC or 120V DC, the high-voltage LED will illuminate, indicating a dangerous voltage. The LED brightness increases with the measured voltage. This function is applicable only to UT18A/B/C/E.

6. Continuity Test

To confirm if a conductor is electrified, a voltage measurement method can be used by measuring voltage at both ends. Connect the two test pens to the object. If the resistance is within 0~100kΩ, the continuity LED (UT18A/B/C) or continuity symbol "?" (UT18D) illuminates, accompanied by a continuous beep. If resistance is within 100kΩ~150kΩ, the continuity LED/symbol may or may not illuminate, and the buzzer may or may not beep. For UT18E, continuity is indicated within 0~60kΩ (LED/symbol illuminates, buzzer beeps), and between 60kΩ~150kΩ, indication may be intermittent. If resistance is >150kΩ, no continuity indication occurs. Before any test, ensure the object is not electrified.

7. Rotation Test (Three-Phase AC Phase Indication)

The measurement must be conducted in accordance with the safety test regulations specified in item 3.

In cases of strong electric field interference or strong radiation, test phase sequence results may be unstable.

The R, L LED or L and R symbol indication is applicable for rotation tests and is only for three-phase AC systems.

1. Voltage Range: 57V~400V (50Hz~60Hz); 100V~400V only for UT18E.
2. Procedure: Hold the main body of the tester. Connect test pen L2 to any phase and L1 to one of the remaining two phases.
3. Indication: R or L LED illuminates. After connecting a test pen to another phase, another LED (L or R) illuminates.
4. Phase Exchange: L or R LED illumination changes accordingly when the position of the two test pens is exchanged.
5. Voltage Display: LED indicates the corresponding voltage, or LCD displays the corresponding voltage value. The displayed voltage is phase voltage against earth, not three-phase voltage.

Figure 4 Description: This diagram illustrates the testing of a three-phase electric system. It shows the connection of test pens to phases L1, L2, and L3, with the tester handle being held to establish a reference terminal.

Note: For three-phase AC systems, connect three measuring terminals. Since the tester has only two test pen terminals, holding the tester handle with a finger (through the ground) establishes the reference terminal. This is crucial for accurate phase sequence indication. If not holding the handle or wearing insulating gloves, accuracy may be affected. Ensure the earth terminal (earth wire or shell) of the three-phase system is in contact with the human body when measuring three-phase power systems below 100V.

8. RCD Test

To reduce disturbance voltage during measurement, an RCD circuit system with lower impedance than the tester's normal measurement mode can be used between the two test pens.

RCD Trip Test: Connect the two test pens to the L and PE terminals of a 230Vac system under normal voltage measurement mode. Press the RCD key "⚡" on both test pens. The RCD system trips, and the LED indicating RCD (UT18B/C/E) or RCD symbol (UT18D) illuminates if the circuit generates AC current higher than 30mA.

Note: If RCD cannot measure for a long time, at 230V, the testing time should be <10s. Continuous measurement is not possible; wait 60s after one test before the next.

Note: In case of no measurement or test, continuously illuminated LED and continuous beeping buzzer after simultaneously pressing RCD keys on both test pens is normal. To avoid functional disorder, do not press two RCD keys outside of RCD testing mode.

9. Silent Mode Selection

The silent mode can be entered while the tester is in standby or normal use. Press the flashlight key for approximately 1 second. The tester beeps, and the LCD displays the silence symbol "?" (UT18C/D/E). In silent mode, all functions are similar to normal mode, except the buzzer is deactivated. To resume normal buzzing mode, press the flashlight key for approximately 1 second; the tester beeps, and the silence symbol "?" disappears from the LCD.

10. Application of Flashlight Function

The flashlight function can be used for operation in dark environments. Lightly touch the flashlight button on the tester panel to turn on the headlamp at the top of the tester, facilitating operation. After use, turn off the light with a light touch on the button.

11. Application of Backlight (Only Applicable for UT18D)

To improve readability of the LCD display in dark environments, the backlight can be turned on. Press the HOLD button for approximately 1 second to turn on the backlight. Press HOLD again for approximately 1 second to turn it off. If the tester enters standby mode while the backlight is on, it will remain illuminated when awakened. The backlight cannot be turned off unless HOLD is pressed again.

12. Application of HOLD Function (UT18C/D/E)

To facilitate reading and recording, the measured data (voltage and frequency values) can be held by lightly touching the HOLD button on the tester. Another light touch releases the hold status and restores normal testing.

13. Battery Replacement

Before using the voltage detector, touch and hold the two probe tips together. If "?" shows and you hear the beeper, or in silent mode, "?" is on. This confirms the battery source is not exhausted; otherwise, it is exhausted.

Continuously flashing negative LED (UT18A/B) or low-voltage symbol "?⬇️" on LCD (UT18C/D/E) during use indicates low battery voltage and the necessity of replacement.

Replace battery according to the following procedures (as shown in Figure 5):

1. Stop measurement and disconnect test pens from the object.
2. Unscrew the battery cover with a screwdriver.
3. Remove the battery cover.
4. Take out the battery to be replaced.
5. Install a new battery according to the battery symbol and direction indicated on the panel.
6. Insert the battery cover and secure it with screws.

Warning: To avoid electric shock, ensure the probes are disconnected from the measured circuit before removing the rear cover. Make sure the rear cover is tightly screwed before using the instrument.

Note: For environmental protection, batteries may be collected and recycled at fixed collection points. Please follow local valid recycling regulations for disposal of batteries.

Figure 5 Description: This figure illustrates the process of battery replacement, showing the removal and insertion of batteries.

14. Equipment Maintenance

No special maintenance is required beyond using the UT18A/B/C/D/E tester as per the manual instructions. In case of any functional abnormality during normal operation, stop using the tester immediately and contact the nearest authorized service center.

15. Equipment Cleaning

Before cleaning, disconnect the tester from the circuit being tested. If the instrument gets dirty during normal use, wipe it with a damp cloth or a small quantity of gentle household cleanser. Do not use acid cleansers or solvents. Do not use the tester within 5 hours after cleaning.

16. Technical Indicator & Function/Parameter Description

Technical Indicators Table

Function	Range	UT18A	UT18B	UT18C	UT18D	UT18E
LCD segment (AC/DC)	6V			5V±1V	5V±1V	5V±1V
LED (AC/DC)	12V	8V±2V	8V±2V	8V±1V	8V±1V	8V±1V
Voltage indication (V)	24V	18V±2V	18V±2V	18V±2V	18V±2V	18V±2V
	50V	38V±4V	38V±4V	38V±4V	38V±4V	38V±4V
	120V	94V±8V	94V±8V	94V±8V	94V±8V	94V±8V
	230V	180V±14V	180V±14V	180V±14V	180V±14V	180V±14V
	400V	325V±15V	325V±15V	325V±15V	325V±15V	325V±15V
	690V	562V±24V	562V±24V	562V±24V	562V±24V	562V±24V
	1000V					820V±30V
Phase rotation test (three-phase voltage)	Voltage range: 57V~400V Frequency: 50Hz~60Hz	✓	✓	✓	✓	✓ (100V~400V only for UT18E)
Continuity test	Resistance range: 0~100kΩ Buzzing and LED illumination	✓	✓	✓	✓ (0~60kΩ, only for UT18E)	✓ (0~60kΩ, only for UT18E)
RCD test	Voltage range: 230V Frequency: 50Hz~400Hz	✓	✓	✓	✓	✓
Polarity measurement	Positive and negative pole	✓	✓	✓	✓	✓
Self-check	All LED illuminated or LCD full-display	✓	✓	✓	✓	✓
Detection without battery	Range: 50VAC~690VAC 120VDC~690VDC	✓	✓	✓	✓	✓ (1000V only for UT18E)

Special Functions Table

Special functions	UT18A	UT18B	UT18C	UT18D	UT18E
Waterproof	IP65	✓	✓	✓	✓	✓
Auto range	Full range	✓	✓	✓	✓	✓
Flashlight	Full range	✓	✓	✓	✓	✓
Low-battery voltage indication	About 2.4V	✓	✓	✓	✓	✓
Over voltage protection	About 750V	✓	✓	✓	✓	✓ (1015V only for UT18E)
Auto standby	Standby current <10uA	✓	✓	✓	✓	✓
Silent mode	Full range	✓	✓	✓	✓	✓
Backlight	Full range				✓
LCD display (voltage)	6V~690V	✓	✓	✓	✓	✓ (1000V only for UT18E)
LCD display (frequency)	40Hz~400Hz			✓	✓	✓

LCD Display Accuracy Indicator Table

Range (AC/DC)	6V	12V/24V	50V	120V	230V/400V/690V	1000V
UT18C	±(1.5%+1)	±(1.5%+2)	±(1.5%+3)	±(1.5%+4)	±(1.5%+5)
UT18D	±(1.5%+1)	±(1.5%+2)	±(1.5%+3)	±(1.5%+4)	±(1.5%+5)
UT18E	±(1.5%+1)	±(1.5%+2)	±(1.5%+3)	±(1.5%+4)	±(1.5%+5)	±(1.5%+5)

17. Function and Parameter Description

• LED voltage range: 12V~690V AC/DC, 1000V AC/DC (only for UT18E).
• LED voltage indication points: 12V, 24V, 50V, 120V, 230V, 400V, 690V, 1000V (only for UT18E).
• LCD voltage range: 6V~690V AC/DC (UT18C/D), 1000V AC/DC (only for UT18E); resolution: 1V, voltage accuracy: ±(1.5%+1~5 Digits).
• Frequency measurement range: 40Hz~400Hz, resolution: 1Hz, accuracy: ±(3%+5Digits).
• Voltage measurement: Auto.
• Buzzing and silent mode is optional.
• Polarity indication: Auto.
• Range selection: Auto.
• Response time: LED<0.1s/LCD<1s.
• Peak current of test circuit: Is<3.5mA (ac/dc).
• Test time: 30s.
• Recovery time: 240s.
• RCD test: Range: 230V (50Hz~400Hz); Current: AC30mA~40mA; Test time <10s, recovery time: 60s.
• Over voltage protection: 750V AC/DC (1015V AC/DC only for UT18E).
• On-off test: 0 kΩ...100kΩ (0kΩ....60kΩ only for UT18E); Accuracy: R_n+50%.
• Rotation test (three-phase AC): Voltage range: 57V~400V; Frequency range: 50 Hz~60Hz (100V~400V only for UT18E).
• Simple test (without battery): Voltage range: 50VAC~690VAC, 120VDC~690VDC (UT18A/B/C, 1000V only for UT18E).
• Working temperature range: -15℃~+45℃.
• Storage temperature range: -20℃~+60℃.
• Working humidity range: ≤85% RH.
• Over voltage protection class: CAT III 690V, CAT IV 600V (UT18E: CAT III 1000V, CAT IV 600V).
• Class of pollution: 2.
• Safety rules: IP65, EN61010-1, EN61243-3:2010.
• Weight: 238g (UT18A), 272g (UT18B/C), 295g (UT18D), 277g (UT18E) (inclusive of battery).
• Dimensions: 272×85×31mm.
• Battery: IEC LR03 (AAA) x 2.