UNI-T UT33+ Series Palm Size Digital Multimeter User Manual

1. Safety Information

Please read and understand all safety instructions and warnings before operating the device. Failure to do so may result in electric shock, injury, or damage to the meter or equipment under test.

1.1. Safety Certification

This product complies with IEC 61010 safety standards, including CAT II: 600V, RoHS, pollution grade II, and double insulation standards.

1.2. Safety Instructions and Precautions

• Do not use the device if it or the test leads appear damaged, or if you suspect the device is not operating properly. Pay particular attention to the insulation layers.
• If test leads are damaged, they must be replaced with ones of the same type or electrical specification.
• When measuring, do not touch exposed wires, connectors, unused inputs, or the circuit being measured.
• When measuring voltage higher than 60 VDC or 36 VACrms, keep your fingers behind the finger guard on the test lead to prevent electric shock.
• If the range of the voltage to be measured is unknown, select the maximum range first and then gradually decrease it.
• Never input voltage and current exceeding the values listed on the device.
• Before switching ranges, ensure to disconnect the test leads from the circuit under test. It is strictly prohibited to switch ranges during measurement.
• Do not use or store the device in high temperature, high humidity, flammable, explosive, or strong magnetic field environments.
• Do not change the internal circuit of the device to avoid damage to the device and users.
• To avoid false readings, replace the battery when the battery indicator appears.
• Use a dry cloth to clean the case; do not use detergents containing solvents.

1.3. Electrical Symbols

• Low battery: Indicates low battery power.
• Electrical ground: Reference point for electrical potential.
• Double insulation: Indicates double insulation for safety.
• High voltage warning: Alerts to the presence of high voltage.
• AC/DC: Indicates alternating current or direct current.
• Warning: General warning symbol.

2. Setup

2.1. Unpacking and Contents

Carefully open the package box and remove the device. Please check if the following items are present and undamaged. Contact your supplier immediately if any items are missing or damaged.

• User manual (1 pc)
• Test leads (1 pair)
• Protective case (1 pc)
• K-type thermocouple (1 pc, included only with UT33C+ model)

Package contents for the UT33+ series multimeter.

2.2. Battery Installation

The device requires two AAA 1.5V batteries. To install or replace batteries:

1. Switch the functional dial to the "OFF" position.
2. Remove the test leads from the input terminals.
3. Carefully remove the protective case from the multimeter.
4. Loosen the screw on the battery cover located on the rear of the device.
5. Remove the battery cover and insert two AAA 1.5V batteries, ensuring correct polarity (+ and -).
6. Replace the battery cover and tighten the screw.
7. Reattach the protective case.

UT33C+ multimeter with its protective case removed, ready for battery access.

3. Operating Instructions

To avoid false readings, always replace the battery if the low battery symbol appears. Pay special attention to the warning signs near the test lead jacks, indicating that the tested voltage or current must not exceed the specified values.

3.1. Device Structure and Components

Familiarize yourself with the main parts of your multimeter:

1. Display Screen: Shows measurement readings and symbols.
2. Function Keys: Used for various settings and modes.
3. Functional Dial: Selects the measurement function.
4. 10A Input Jack: For high current measurements (up to 10A).
5. COM Jack: Common (return) terminal for all measurements.
6. Remaining Inputs Jack (VΩmA): For voltage, resistance, capacitance, and low current measurements.

Front view of the UT33D+ multimeter, showing its display and controls.

Detailed view of the multimeter's components and features.

3.2. Key Functions

• UT33A+:
  • SEL/REL Button: Press to switch between AC and DC modes for mV and current (I) measurements. Also used for relative measurement (REL) function.
  • HOLD/ Button: Press to enter or exit data hold mode. Long press for over 2 seconds to turn the backlight on/off.
• UT33B+/C+/D+:
  • HOLD/SEL Button: Press to enter or exit data hold mode. In continuity/diode mode, press to cycle between the two modes.
  • Button: Press to turn the backlight on/off.

3.3. Measurement Operations

Always ensure the test leads are correctly inserted into the appropriate jacks and the functional dial is set to the desired measurement function before connecting to a circuit.

3.3.1. AC/DC Voltage Measurement

1. Switch the functional dial to the "V~" (AC Voltage) or "V-" (DC Voltage) position.
2. Insert the black test lead into the COM jack and the red test lead into the "VΩmA" jack.
3. Connect the test leads in parallel with the load or circuit to be measured.

Warning:

• Do not measure voltage exceeding 600Vrms, as this may expose users to electric shock and damage the device.
• If the voltage range is unknown, always select the maximum range first and then reduce it accordingly.
• Exercise extreme caution when measuring high voltage to avoid electric shock.
• Before using the device for critical measurements, it is recommended to measure a known voltage for verification.

3.3.2. Resistance Measurement

1. Switch the functional dial to the "Ω" position.
2. Insert the black test lead into the COM jack and the red test lead into the "VΩmA" jack.
3. Connect the test leads in parallel with the resistor to be measured.

Warning:

• Before measuring resistance, ensure the power supply to the circuit is off and all capacitors are fully discharged.
• If the resistance when probes are shorted is more than 0.5Ω, check if the test leads are loose or damaged.
• If the resistor is open or over the range, the "OL" symbol will be displayed.
• When measuring low resistance, the test leads may introduce a 0.1Ω to 0.2Ω measurement error. For accurate measurements, subtract the value displayed when the two test leads are shorted.
• When measuring high resistance (above 1MΩ), it is normal for readings to take a few seconds to stabilize. Use short test wires for quicker stabilization.

Measuring resistance on a circuit board with the UT33D+ multimeter.

3.3.3. Continuity Measurement

1. Switch the functional dial to the "•)))" position.
2. Insert the black test lead into the COM jack and the red test lead into the "VΩmA" jack.
3. Connect the test leads to the points to be tested.

• If the measured resistance is ≤10Ω, the circuit is in good conduction status, and the buzzer will sound.
• If the measured resistance is >50Ω, the circuit is in an open status, and the buzzer will not sound.

Warning:

• Before measuring continuity, switch off all power supplies and fully discharge all capacitors.

3.3.4. Diode Measurement

1. Switch the functional dial to the "⟘" position.
2. Insert the black test lead into the COM jack and the red test lead into the "VΩmA" jack.
3. Connect the test leads to the diode in parallel.

• The "OL" symbol appears when the diode is open or its polarity is reversed.
• For a silicon PN junction, a normal value is typically between 500mV and 800mV (0.5V to 0.8V).

Warning:

• Before measuring PN junction, switch off the power supply to the circuit and fully discharge all capacitors.

3.3.5. Capacitance Measurement (UT33A+ only)

1. Switch the functional dial to the capacitance test position.
2. Insert the black test lead into the COM jack and the red test lead into the "VΩmA" jack.
3. Connect the test leads in parallel with the capacitor.

• When there is no input, the device displays a fixed value (intrinsic capacitance). For small capacitance measurements, subtract this intrinsic capacitance from the measured value to ensure accuracy.
• Users can utilize the relative measurement function (REL) to automatically subtract the intrinsic capacitance.

Warning:

• If the tested capacitor is shorted or its capacity exceeds the specified range, the "OL" symbol will be displayed.
• When measuring large capacitors, it may take a few seconds to obtain stable readings.
• Before measuring capacitors (especially high-voltage capacitors), ensure they are fully discharged.

3.3.6. DC Current Measurement

1. Switch the functional dial to the DC current test position (e.g., 200μA, 20mA, 10A).
2. Insert the black test lead into the COM jack. Insert the red test lead into the "VΩmA" jack for low currents (up to 200mA) or the "10A" jack for high currents (up to 10A).
3. Connect the test leads in series with the circuit to be tested.

Warning:

• Before measuring, switch off the power supply to the circuit and carefully check the input terminal and range position.
• If the range of the measured current is unknown, select the maximum range first and then reduce it accordingly.
• Replace fuses with the same type: 10A jack uses a 10A/250V fast fuse (Φ5×20mm); VΩmA jack uses a 200mA/250V fast fuse (Φ5×20mm).
• When measuring, do not connect the test leads in parallel with any circuit, as this risks damage to the device and potential injury.
• If the tested current exceeds 10A, each measurement duration should be less than 10 seconds, with a 15-minute cool-down period before the next test.

Input terminal connections for various measurements.

3.3.7. AC Current Measurement (UT33A+ only)

The procedure for AC current measurement is similar to DC current measurement. Please refer to the instructions in Section 3.3.6 "DC Current Measurement".

3.3.8. Battery Measurement (UT33B+ only)

1. Switch the functional dial to the battery test position.
2. Insert the black test lead into the COM jack and the red test lead into the "VΩmA" jack.
3. Connect the test leads in parallel with the battery, ensuring the red test lead is on the positive (+) pole and the black test lead is on the negative (-) pole.

The multimeter will display the battery status:

• "Good": Normal status.
• "Low": Low power but still functional.
• "Bad": Replace or recharge the battery.

Battery display thresholds (approximate):

• 1.5V Battery (Load Resistance: 30Ω):
  • "Good": Voltage ≥1.31V
  • "Low": Voltage 0.95V ~ 1.31V
  • "Bad": Voltage ≤0.94V
• 9V Battery (Load Resistance: 900Ω):
  • "Good": Voltage ≥7.8V
  • "Low": Voltage 5.7V ~ 7.7V
  • "Bad": Voltage ≤5.6V
• 12V Battery (Load Resistance: 600Ω):
  • "Good": Voltage ≥10.5V
  • "Low": Voltage 7.6V ~ 10.4V
  • "Bad": Voltage ≤7.5V

Warning:

• If the measured voltage is <0.2V (0.05V-0.19V), no indicator status will be displayed, and the reading will flash for 3 seconds every 6-second interval.

3.3.9. Temperature Measurement (UT33C+ only)

1. Switch the functional dial to the temperature test position (°C or °F).
2. Insert the K-type thermocouple into the device's dedicated input jacks.
3. Fix the temperature probe to the object to be measured. Read the value once it stabilizes.

Warning:

• Only K-type thermocouples are applicable. The measured temperature should not exceed 250°C / 482°F.

3.3.10. NCV Measurement (UT33D+ only)

1. Switch the functional dial to the "NCV" position.
2. Place the device near the measured object.

• The number of "-" symbols displayed indicates the intensity of the electric field. More "-" symbols and a higher buzzer frequency correspond to a higher electric field intensity.

The UT33+ series multimeters, each with unique feature upgrades.

4. Troubleshooting

• False Reading: If the battery indicator appears, replace the batteries immediately to ensure accurate readings.
• "OL" Symbol Displayed: This indicates an open circuit or that the measured value is over the selected range. Adjust the range or check the circuit connection.
• Unstable Readings: In mV range without a load, readings might be unstable. They will stabilize once a load is connected. High resistance measurements (above 1MΩ) may also take a few seconds to stabilize.
• Buzzer Notifications:
  • Continuous beeping when input voltage ≥600V (AC/DC) or input current >10A (AC/DC) indicates the measurement range limit has been reached.
  • Five continuous beeps 1 minute before auto shutdown.
  • One long beep before the device shuts down.
• Auto Shutdown: The device automatically shuts down after 15 minutes of inactivity. To disable this feature, long-press the HOLD button while turning the device on.
• Low Power Warnings:
  • If battery voltage is <2.5V, the battery symbol appears and flashes for 3 seconds every 6 seconds. The device can still operate in this state.
  • If battery voltage is <2.2V, a solid battery symbol appears, and the device will cease to function.

5. Specifications

5.1. General Specifications

• Accuracy: ±(% of reading + numerical value in least significant digit slot), 1 Year Warranty.
• Ambient Temperature: 23°C ±5°C (73.4°F ±9°F).
• Ambient Humidity: ≤75% RH.
• Operating Temperature: 0°C ~ 40°C (32°F ~ 104°F).
• Storage Temperature: -10°C ~ 50°C (14°F ~ 122°F).
• Relative Humidity: 0°C~30°C: ≤75% RH, 30°C~40°C: ≤50% RH.
• Operating Altitude: 0 ~ 2000m.
• Dimension: (134 × 77 × 47) mm.
• Weight: Approximately 206g (including battery).
• Power: 1.5V battery (R03) x 2.
• Display Size: 66mm x 51mm.
• Product Color: Red and grey.
• Max Display: 1999.
• Over Range Display: "OL".
• Update Rate: 2~3 times/second.
• Range Select: Auto range (UT33A+); Manual range (UT33B+/C+/D+).
• Backlight: Manual on, auto shut off after 30 seconds.
• Polarity: "-" symbol displays for negative polarity signal.
• Data Hold Function: Symbol displays when activated.
• Low Battery Power: Symbol displays when battery power is low.
• Electromagnetic Compatibility: In fields with less than 1V/m radio frequency, total accuracy is designated accuracy + 5% of measurement range. In fields with more than 1V/m radio frequency, accuracy is not specified.

Note:

• To ensure accuracy, operating temperature should be within 18°C~28°C.
• Temperature Coefficient = 0.1 * (specified accuracy) / °C (<18°C or >28°C).

5.2. Detailed Measurement Specifications

5.3. Feature Comparison

Overview of 24 major innovation technology designs.

6. Maintenance

Warning: Before opening the rear cover, ensure the power supply is switched off and test leads are removed from the input terminals and the circuit.

6.1. General Maintenance

• Clean the case with a damp cloth and a mild detergent. Do not use abrasive cleaners or solvents.
• If any malfunction occurs, stop using the device immediately and send it for maintenance.
• All maintenance and service procedures must be conducted by qualified professionals or designated service departments.

6.2. Battery Replacement

Refer to Section 2.2 "Battery Installation" for detailed instructions on replacing the AAA 1.5V x 2 batteries.

6.3. Fuse Replacement

To replace a fuse:

1. Switch the functional dial to the "OFF" position.
2. Remove the test leads from the input terminals.
3. Loosen both screws on the rear cover.
4. Carefully remove the rear cover to access the fuses.
5. Replace the blown fuse with a new one of the correct specification:
   • F1 Fuse (for μA/mA range): 0.2A/250V fast fuse (Φ5×20mm ceramic tube).
   • F2 Fuse (for 10A range): 10A/250V fast fuse (Φ5×20mm ceramic tube).
6. Replace the rear cover and tighten the screws.

Internal PCB board design of the UT33+ series.

7. User Tips

• Temperature Sensor (UT33C+): The K-type thermocouple for temperature measurement is included with the UT33C+ model. You do not need to purchase it separately.
• Always start measurements with the highest possible range if the value is unknown to prevent overloading the meter.
• For accurate low resistance or small capacitance measurements, utilize the relative measurement (REL) function if available on your model.
• Regularly check the battery indicator and replace batteries promptly to ensure reliable performance.
• Keep the multimeter clean and free from dust and moisture to prolong its lifespan.

8. Warranty and Support

The UNI-T UT33+ series multimeters come with a 1-year warranty from the date of purchase, covering manufacturing defects. For technical support, service, or warranty claims, please contact:

Please retain your purchase receipt as proof of purchase for warranty purposes.