UNI-T UT33B/C/D Multimeter User Manual

Introduction

The UNI-T UT33B, UT33C, and UT33D are 3½ digit universal measuring instruments combining modern design and high functionality. They can measure AC/DC voltage, AC/DC current, electrical resistance, temperature, diodes, and test continuity. They are suitable for maintenance tasks. This manual applies to all UT33B/UT33C/UT33D models unless otherwise specified.

Safety Precautions

Warning: Read the safety information and proper usage rules carefully before using the instrument to avoid electric shock.

• Before each measurement, check the instrument's condition. Do not use if damaged or if any part is missing. Pay special attention to the insulation around the input terminals and the test leads with probes.
• Do not connect the instrument to voltages higher than indicated between the input terminals. The rotary switch must be in the correct position for measurement; changing it during measurement can damage the instrument.
• Be particularly careful when measuring voltages above 60VDC or 42VAC to avoid electric shock.
• Do not use the instrument in conditions of extreme humidity, temperature, strong magnetic fields, or explosive environments.
• If the low battery indicator appears on the display, replace the battery as soon as possible. Continuing to measure may lead to incorrect readings and potential electric shock.
• Before opening the instrument, disconnect the test leads and the temperature probe, and turn off the instrument.
• The instrument is intended for indoor use only.
• If the instrument is not in use, turn it off. If it will not be used for a long time, remove the battery.
• Regularly check the battery. If it leaks or is damaged, replace it immediately.

Package Contents

The package includes the measuring instrument, manual, test leads, contact temperature probe (UT33C only), and a carrying case. If any of these items are missing, contact your dealer.

Safety Information

The multimeter complies with IEC61010 standards. Use the instrument only for the purposes stated in this manual.

Proper Usage Rules

To prevent damage to the instrument or electric shock, follow these rules:

• Before every measurement, check the instrument's condition. Do not use if it is damaged or missing parts. Pay attention to the insulation around the input terminals and the test leads.
• Do not connect to voltages higher than indicated. Ensure the rotary switch is in the correct position for measurement. Do not change the position during measurement.
• Exercise extreme caution when measuring voltages above 60VDC or 42VAC to prevent electric shock.
• Avoid using the instrument in extreme humidity, temperature, strong magnetic fields, or explosive environments.
• Replace the battery promptly when the low battery indicator appears to ensure accurate readings and prevent electric shock.
• Disconnect test leads and temperature sensor, and turn off the instrument before opening it.
• The instrument is designed for indoor use.
• Turn off the instrument when not in use. Remove the battery if storing for extended periods.
• Regularly inspect the battery for leaks or damage and replace it immediately if necessary.

International Electrical Symbols

• ~ : Alternating Current (AC)
• ~ : Alternating Current (AC)
• --- : Direct Current (DC)
• : Ground
• : Double Insulation
• : Low Battery
• : Diode
• : Fuse
• : Continuity Test
• : Safety Rules
• CE : CE Standard Compliance

Component Layout

1. LCD Display
2. HOLD Button
3. Display Backlight Button
4. Rotary Switch
5. COM Input Jack (Common)
6. 10A Input Jack
7. Universal Input Jack

Function Buttons

HOLD Button

Press once to freeze the displayed value. Press again to release. The display shows 'H' when frozen.

BLUE Button

Press once to turn on the display backlight. Press again to turn it off. The backlight does not turn off automatically.

Measurements

DC Voltage

Never attempt to measure voltages above 500V, even if the instrument displays a reading, as this may damage the instrument or cause electric shock.

Measurement Ranges: 200mV, 2000mV, 20V, 200V, 500V

Set the rotary switch to the correct range and connect the potential to be measured between the universal jack and the common jack. The measured value will be displayed.

If the voltage is unknown, start with the 500V range and gradually decrease the range for desired resolution.

If the measured range is exceeded, the display will show '1'.

The input impedance for each range is 10MΩ, which may cause inaccurate measurements in circuits with high impedance. If the circuit's impedance is around 10kΩ, the error is negligible (less than 0.1%).

AC Voltage

Never attempt to measure voltages above 500Vrms, even if the instrument displays a reading, as this may damage the instrument or cause electric shock.

Measurement Ranges: 200V, 500V

Set the rotary switch to the correct range and connect the potential to be measured between the universal jack and the common jack. The measured value will be displayed.

The displayed value is the RMS value of a sine wave.

If the voltage is unknown, start with the 500V range and gradually decrease the range for desired resolution.

If the measured range is exceeded, the display will show '1'.

The input impedance for each range is 10MΩ, which may cause inaccurate measurements in circuits with high impedance. If the circuit's impedance is around 10kΩ, the error is negligible (less than 0.1%).

DC Current

Warning: Do not attempt to measure current in a circuit where the voltage between terminals exceeds 60V. Do not short-circuit the input terminals during current measurement.

Model UT33B Measurement Ranges: 200μA, 200mA, 10A

Model UT33C/UT33D Measurement Ranges: 2000μA, 20mA, 200mA, 10A

To measure current:

• Turn off the device being measured.
• Discharge any high-voltage capacitors.
• Set the rotary switch to the correct range and connect the red test lead to the universal or 10A jack, and the black test lead to the common jack.
• Break the current path and connect the red lead to the positive side of the current path and the black lead to the negative side.
• Turn on the device being measured.
• The measured value will be displayed.
• If the current is unknown, start with the 10A range and gradually decrease the range for desired resolution.

Electrical Resistance Measurement

Before measuring electrical resistance, discharge all high-voltage capacitors.

Model UT33B/UT33C Measurement Ranges: 200Ω, 2000Ω, 20kΩ, 200kΩ, 20MΩ

Set the rotary switch to the correct range and connect the resistor to be measured between the universal and common jacks. The measured value will be displayed.

The test leads can introduce an inaccuracy of 0.1 to 0.3 Ω. For high resistance measurements (above 1 MΩ), it may take longer for the reading to stabilize.

Diode Measurement and Continuity Test

Diode Measurement

Turn off the device being measured. Discharge any high-voltage capacitors.

The diode test is used to measure diodes, transistors, and other semiconductor components. During the diode test, current flows through the semiconductor junction, and the residual voltage across the junction is measured. The residual voltage for a functional silicon semiconductor junction is typically between 0.5V and 0.8V.

If measuring a diode not connected in a circuit, connect the cathode to the common terminal and the anode to the universal terminal.

Set the rotary switch to the correct range. The measured value will be displayed.

If the diode is faulty or reverse-biased, the display will show '1'.

Model UT33C/UT33D Continuity Test:

Set the rotary switch to the correct range. Connect the circuit to be measured between the universal and common terminals using the test leads. The instrument will beep if the tested circuit has less than 70Ω. If the display shows '1', the circuit is open.

Temperature Measurement

Model UT33C:

Temperature measurement range is -40°C to +1000°C. Connect the temperature probe between the universal and common terminals. Set the rotary switch to the correct range. The measured value will be displayed.

Note: If the temperature probe is not connected, the instrument measures internal temperature. The included temperature probe can be used for measurements up to 250°C.

Model UT33B: Battery Test

Insert the test leads into the universal and common terminals. Set the rotary switch to the correct range. Connect the test leads to the battery, ensuring correct polarity. The measured battery voltage will be displayed.

Model UT33D:

Set the rotary switch to the correct range. A square wave output signal will appear on the universal terminal relative to the common terminal. The frequency is approximately 50 Hz. The output voltage is greater than 3V with a 1MΩ load.

General Specifications

• Maximum voltage between any terminal and earth ground must not exceed 500Vrms.
• The general terminal is protected by a fuse: F315mA, 250V.
• The 10A terminal is unfused.
• Range switching is manual.
• Maximum displayable reading is 1999.
• Measurement speed: 2 to 3 times per second.
• Temperature:
  Operating: 0 - 40°C
  Storage: -10 to 50°C
• Relative Humidity: <= 75% (0 - 30°C), <= 50% (31 - 40°C)
• Altitude:
  Operating: up to 2000m
  Storage: up to 10000m
• Power Supply: 1 x 9V 6F22 battery.
• Low battery is indicated by a battery icon on the display.
• A negative input value is indicated by '-'.
• Overload is indicated by '1'.
• Dimensions: 130x73.5x35 mm
• Weight: 156g (including battery)
• Safety Compliance: IEC61010 CAT.I 600V overvoltage protection, double insulation. CE certified.

Accuracy

Accuracy is specified at an operating temperature of 23°C ± 5°C and humidity of 75%.

DC Voltage

• 200mV to 200V: ± 0.5% + 2
• 500V: ± 0.8% + 2

AC Voltage

• All ranges: ± 1.2% + 10

Note: Input impedance is approximately 5MΩ. Input frequency is 40Hz to 400Hz. The display shows the RMS value of a sine wave.

DC Current

• 200μA to 200mA: ± 1.2% + 2
• 10A: ± 2% + 5

Note: For high current measurements on the 10A range, after measuring for more than 15 seconds, let the instrument rest for 15 minutes.

Electrical Resistance

• 200Ω: ± 0.8% + 5
• 2000Ω to 200kΩ: ± 0.8% + 2
• 20MΩ: ± 1% + 5
• 200MΩ: ± 5% + 10

Diode Measurement and Continuity Test

• Diode measurement resolution: 1mV
• Continuity test resolution: 1Ω

Temperature Measurement

• -40 to 150°C: ± 1% + 3
• 150 to 1000°C: ± 1.5% + 15

Battery Test

• 12V: 10mV resolution, 240Ω internal resistance
• 9V: 10mV resolution, 1.8kΩ internal resistance
• 1.5V: 10mV resolution, 30Ω internal resistance

Maintenance

Do not attempt to repair the measuring instrument yourself unless you are qualified. Avoid the risk of electric shock or instrument damage.

• Do not expose the instrument to excessive moisture.
• Clean the test leads regularly. Dirt on the leads can cause inaccurate measurements.
• If the instrument is not in use, turn it off. If it will not be used for a long time, remove the battery.
• Do not store the instrument in strong magnetic fields, explosive or flammable environments, or in places with high humidity or high temperatures.

Battery Replacement

When the low battery indicator appears, replace the battery as soon as possible. Continuing to measure may lead to incorrect readings and potential electric shock.

Disconnect the test leads and turn off the instrument. Unscrew the rear panel, replace the battery with an identical one, and screw the rear panel back on.

Fuse Replacement

Disconnect the test leads and turn off the instrument. Unscrew the rear panel, remove the blown fuse by pulling one end, and slide it out of its holder. Insert a new, identical fuse into the holder, ensuring it is securely seated, and screw the rear panel back on.

Fuse type: F315mA, 250V, Φ5x20mm

Fuse replacement is rare. Frequent fuse blowing indicates improper use.

Warranty

The warranty for this instrument is 24 months from the date of sale. The warranty does not cover defects caused by improper use, such as incorrect connection to power or signal sources, overload, or damage from external factors like transportation, water, corrosive substances, heat, etc.

To claim warranty service, present this warranty card and proof of purchase (receipt or invoice).

Date of Sale: ____________________

Serial Number: ____________________

Seller's Stamp and Signature: ____________________