NJTY T28B Digital Multimeter User Manual

Introduction

This manual provides detailed instructions for the safe and effective use of your NJTY T28B Digital Multimeter. Please read this manual thoroughly before operation and keep it for future reference. The NJTY T28B is a versatile digital multimeter designed for accurate measurement of various electrical parameters, suitable for both professional and DIY electrical tasks.

Safety Information

The Meter conforms to IEC61010-1 CAT III 600V, 1000V CAT II IEC61010 and pollution level II. A Warning identifies conditions and procedures that are dangerous to the user. To prevent possible electrical shock, fire, or personal injury:

• Do not alter the Product and use only as specified, or the protection supplied by the Product can be compromised.
• Do not use the Product around explosive gas, vapor, or in damp or wet environments.
• Do not operate the Product with covers removed or the case open. Hazardous voltage exposure is possible.
• Do not apply more than the rated voltage, between the terminals or between each terminal and earth ground.
• Do not use test leads if they are damaged. Examine the test leads for damaged insulation, exposed metal, or if the wear indicator shows. Check test lead continuity.
• Use the correct terminals, function, and range for measurements.
• The range switch should be placed in the correct range position.
• The input signal is not allowed to exceed the specified limit value to prevent electric shock and damage to the instrument.
• When measuring televisions or switching power supplies, be aware that there may be pulses in the circuit that can damage the circuit.
• Remove the batteries if the Product is not used for an extended period of time, or if stored in temperatures above 50°C.

Safety Symbols

Product Familiarization (Overview)

The NJTY T28B Digital Multimeter features a user-friendly design with a clear LCD screen and intuitive controls. Below is an overview of its main components and functions.

1. Flashlight
2. Alarm Indication Light
3. NCV Sensor
4. LCD Screen
5. Function Switching & Lock Button
6. Frequency/Duty Cycle /Capacitance ZERO
7. Flashlight & Backlight Button
8. Manual/Auto-ranging Switch
9. mA Input Socket (MAX 600mA)
10. 20A Input Socket (MAX 20A)
11. VΩHzC Socket
12. COM Socket

Physical Features

Strong Magnet Feature

The multimeter is equipped with a strong magnet on its back, allowing it to be securely attached to metal surfaces for hands-free operation during measurements.

Setup

Package Contents

Before starting, please ensure all items are present in the package:

• 1x NJTY T28B Digital Multimeter
• 1x Test Leads (Red and Black)
• 1x K-type Thermocouple
• 2x Ceramic Fuse Tubes
• 1x Carrying Case
• 1x Instruction Manual (this document)
• 4x 1.5V AAA Batteries (Note: Batteries are not included in some packages. Please check your specific product offering.)

Battery Installation

The multimeter requires 4x 1.5V AAA batteries (not included in all packages). Follow these steps to install or replace batteries:

1. Turn off the meter.
2. Pull out all test leads from the input sockets.
3. Use a screwdriver to loosen the screws securing the battery cover or back cover.
4. Remove the battery cover or back cover.
5. Insert new 4x 1.5V AAA batteries, ensuring correct polarity.
6. Install the battery cover or back cover, and tighten the screws.

Operating Instructions

General Measurement Guidelines

• Check the battery first; if the battery symbol is displayed, the battery needs to be changed.
• The warning signal (triangle with exclamation mark) besides sockets warns of the maximum input voltage and current.
• Switch to the right range before measurement.
• The red lead is positive in polarity, the black lead is negative.

Manual and Auto-ranging

The Meter defaults to Auto-range, indicated by 'AUTO' on the display. Short-press the 'RANGE' button to enter Manual range. In Manual Range mode, press 'RANGE' to increment the range. After the highest range, the Meter wraps to the lowest range. Press 'RANGE' for 2 seconds to return to Auto-range mode, where the Meter automatically selects the range with the best resolution.

DC/AC Voltage Measurement

1. Insert the black test lead into the 'COM' port and the red test lead into the 'VΩHzC' port.
2. Switch the rotary knob to the 'mV' or 'V' range. 'DC' signal will be displayed for DC voltage test. Press 'FUNC HOLD' button to switch to AC voltage test ('AC' will be displayed).
3. Connect the test leads to the loaded circuit.

Note: The voltage above DC1000V or AC750V cannot be measured; otherwise, the instrument may be damaged. In AC/DC 600mV and AC 6V ranges, the Meter may display numbers even with no input. Short-circuit the 'VΩHzC' and 'COM' ports; if the display returns to zero, the meter is normal.

Non-contact Voltage (NCV) Detection

1. Turn the rotary knob to NCV.
2. Gradually approach the NCV probe to the detected point.
3. When the meter senses weak AC signals, the yellow indicator lights up and beeps slowly. For strong AC signals, the red indicator lights up and beeps quickly.

Note: Do not rely solely on non-contact voltage detectors to determine voltage presence, as factors like socket depth or insulation thickness can affect readings. Induced voltage or external interference (flashlights, motors) may trigger false positives.

Current Measurement (DC/AC)

1. Insert the black test lead into the 'COM' port. For currents under 600mA, insert the red test lead into the 'mA' port. For currents between 600mA and 20A, insert the red test lead into the '20A' port.
2. Switch the rotary knob to the 'A' or 'mA' range. 'DC' signal will be displayed for DC current test. Press 'FUNC HOLD' to switch to AC current test ('AC' will be displayed).
3. Disconnect the circuit to be tested. Connect the black test lead to the lower voltage end of the disconnected circuit and the red test lead to the higher voltage end. Then connect the test leads to the loaded circuit.

Note: 'OL' indicates overload; switch to a higher range. Do not attempt current measurement if the voltage between the open circuit and ground exceeds 250V. Ensure the fuse is intact. Turn off power to the circuit before connecting the multimeter. Exercise caution with high voltage to prevent electric shock.

Resistance Measurement

1. Insert the black test lead into the 'COM' port and the red test lead into the 'VΩHzC' port.
2. Switch the rotary knob to the 'Ω' range.
3. Connect the test leads to the resistor to be tested.

Note: 'OL' means overload or open circuit. If the tested resistor > 60MΩ, it may take a few seconds to read. Before testing, ensure the circuit is powered off and high-voltage capacitors are discharged. For low resistance, short-circuit test leads, read their resistance, and subtract this value from the measured resistance.

Diode Measurement

1. Insert the black test lead into the 'COM' port and the red test lead into the 'VΩHzC' port.
2. Switch the rotary knob to the diode symbol and press 'FUNC HOLD' button twice. ('+' will be displayed).
3. Touch the diode anode with the red probe and the cathode with the black probe.

Note: 'OL' will be displayed if open-circuited or if test leads are connected in reverse polarity. A normal diode in circuit will show a forward voltage drop of 0.5V to 0.8V.

Continuity Measurement

1. Insert the black test lead into the 'COM' port and the red test lead into the 'VΩHzC' port.
2. Switch the rotary knob to the continuity symbol and press 'FUNC HOLD' button. ('♪' will be displayed).
3. Contact the probes to the measured circuit or resistance.
4. The Meter will buzz and the indicator light will be yellow if resistance is less than 40Ω. If resistance is >40Ω and <60Ω, the buzzer will not ring, and the indicator light will be red.

Note: Before continuity testing, ensure the circuit is powered off and high-voltage capacitors are discharged.

Capacitance Measurement

1. Insert the black test lead into the 'COM' port and the red test lead into the 'VΩHzC' port.
2. Switch the rotary knob to the capacitance symbol.
3. Connect the test leads to the circuit to be tested.

Note: Before testing, ensure the circuit is powered off and high-voltage capacitors are discharged. Large capacitance values may take time to stabilize. Observe polarity for correct connection.

Frequency/Duty Cycle Measurement

1. Insert the black test lead into the 'COM' port and the red test lead into the 'VΩHzC' port.
2. Switch the rotary knob to 'Hz%' and use the 'Hz/%/A' button to toggle between Frequency or Duty Ratio.
3. Connect the test leads to the circuit to be tested.

Note: Do not test any voltage higher than 250V to prevent electric shock or damage.

Temperature Measurement

1. Turn the rotary knob to '°C'. The meter will display the ambient temperature.
2. Switch between '°C' or '°F' by pressing the 'FUNC HOLD' button.
3. Insert the thermocouple into the instrument: positive (red) into 'VΩHzC' input, negative (black) into 'COM' input.
4. Contact the measured object with the thermocouple probe.

Note: When measuring temperature with thermocouples, the probe should not touch charged objects to avoid damage or electric shock.

Backlight and Flashlight Function

• Press the 'light bulb' button to toggle the backlight on and off.
• Press and hold the 'light bulb' button for 2 seconds to turn on the flashlight and backlight simultaneously. Press again to turn them off.
• The backlight and flashlight automatically turn off after 30 seconds.

Data Hold

In Display HOLD mode, the Meter freezes the display and 'H' shows on the display. Press the 'FUNC HOLD' button for 2 seconds to activate/deactivate Display HOLD. To avoid electric shock, when Display HOLD is activated, be aware that the display will not change.

Auto Power Off

The Auto Power Off function is enabled by default at boot, indicated by the 'APO' symbol. Without any operation for about 15 minutes, the Meter will automatically turn off. Press and hold both 'FUNC HOLD' to turn on the meter; this will cancel the auto power off function.

Maintenance

Cleaning

• Turn off the power to the Meter and remove the test leads.
• Wipe the case with a damp cloth and mild detergent.
• Dirt or moisture in the terminals can affect readings.
• If there is any abnormality, stop using the meter immediately.

Battery & Fuse Replacement

Refer to the "Battery Installation" section under Setup for detailed instructions on replacing batteries. For fuse replacement:

• Only use the specified fuse (600mA / 250V, 20A / 250V fast melt fuse) to avoid electric shock or personal injury.
• Turn off and check that the test has been disconnected from the measured circuit before opening the battery cover and replacing the new fuse.

Troubleshooting

This section addresses common issues and their solutions. Always ensure safety precautions are followed before troubleshooting.

• Meter displays 'OL' (Overload): This indicates that the measured value exceeds the current range. Switch to a higher range. For resistance or diode measurements, 'OL' can also mean an open circuit.
• Inaccurate Readings:
  • Check battery level; replace if low.
  • Ensure test leads are not damaged and have good continuity.
  • Verify correct terminals, function, and range are selected.
  • Clean terminals if dirt or moisture is present.
  • For low resistance measurements, perform a short-circuit test of the leads and subtract their resistance from the reading.
• Meter displays numbers in AC/DC 600mV and AC 6V ranges without input: This is normal. Short-circuit the 'VΩHzC' and 'COM' ports; if the display returns to zero, the meter is functioning correctly.
• Meter does not turn on or turns off unexpectedly:
  • Check battery installation and charge.
  • The auto power off function may have activated after 15 minutes of inactivity. Press and hold 'FUNC HOLD' to restart.
• NCV detection issues: Be aware that external interference (flashlights, motors) or induced voltage can affect NCV readings. Do not rely solely on NCV for voltage presence.

Specifications

For detailed specifications, you may also refer to the official user manual PDF: NJTY T28B User Manual (PDF)

AC Voltage Specifications

DC Voltage Specifications

AC Current Specifications

DC Current Specifications

Frequency Specifications

Capacitance Specifications

Resistance Specifications

Diode / Continuity Specifications

Temperature Specifications

User Tips

• Always double-check your range selection before making a measurement to prevent damage to the meter or the circuit.
• Utilize the kickstand for hands-free operation, especially when working on complex circuits.
• The strong magnet feature is useful for attaching the multimeter to metal surfaces, freeing up your hands.
• Remember to use the backlight and flashlight in dimly lit environments for better visibility.
• For temperature measurements, ensure the thermocouple probe does not touch live circuits.

Warranty and Support

For warranty information and customer support, please refer to the seller's terms and conditions or contact the point of purchase. Keep your purchase receipt as proof of purchase.