NJTY 88A Analog Multimeter User Manual

1. Introduction

This series of multimeters are high-sensitivity pointer-type multimeters made of rare earth magnetic materials, covered with soft rubber sleeves, shockproof and drop-resistant. Designed to measure a wide range, it can measure DC voltage and current, AC voltage and current, resistance, capacitance, frequency, diode forward voltage drop, Zener tube, transistor hFE parameters and circuit continuity, battery power, infrared remote control emission signal detection, and fire line discrimination.

2. Safety Information

When using this instrument, the user must comply with all standard safety procedures to prevent electric shock and misuse of instruments.

2.1. General Precautions

• Always use the provided test leads and ensure they are in good condition.
• Avoid using the meter or test leads if damaged.
• Do not touch exposed conductors or buses when working around them.
• Do not use this instrument near explosive gas, vapor, or dust.
• Always use the correct input terminal, function, and range for measurement.
• Do not exceed the input limit value specified for each range.
• Avoid touching unused inputs when the meter is connected to a live circuit.
• Exercise caution to avoid electric shock when measured voltage exceeds 60VDC or 30VAC.
• When measuring with a test lead, place your finger behind the protective ring.
• Before changing the range, ensure the test pen has left the circuit under test.
• Before performing resistance, diode, capacitance, or continuity measurement, ensure the circuit under test's power supply is cut off and all high-voltage capacitors are discharged.
• Do not measure resistance, capacitance, or perform continuity tests on live circuits.

2.2. Input Protection Measures

• Voltage Measurement: The highest input voltage that can be withstood is AC and DC 1000V (V/Ω jack) / 2500V (2500V jack).
• Frequency, Resistance, Continuity, Diode Measurement: Can withstand no more than 250V AC voltage or equivalent RMS voltage.
• Current Measurement (μA and mA): Protected by a fuse or a self-recovery fuse. If a fuse blows, replace it. If a self-recovery fuse activates, wait 30 seconds before measuring again to ensure accuracy.

3. Panel Indication

The following diagram illustrates the key components of the multimeter's front panel:

1. Dial: Analog display for readings.
2. Pointer to zero: Adjustment for mechanical zero.
3. hFE test socket: For transistor hFE parameter measurement.
4. Position rotary switch: Selects measurement function and range.
5. VΩmA input socket: Input for voltage, resistance, and current measurements.
6. COM input socket: Common (negative) input terminal.
7. 10A input socket: Input for high DC current measurements (up to 10A).
8. 2500V input socket: Input for high AC/DC voltage measurements (up to 2500V).
9. Resistor zeroing knob: Adjusts pointer to zero for resistance measurements.
10. Infrared receiving window: For infrared remote control emission signal detection.
11. Infrared and live wire identification indicator light: Indicates detection of infrared signals or live wires.

4. Setup

4.1. Battery Installation

The instrument requires two 1.5V AAA batteries for power. Ensure batteries are correctly installed in the battery compartment. If the resistance scale adjustment is less than zero, it indicates low battery and requires replacement to maintain measurement accuracy and prevent electrolyte leakage.

To replace batteries:

1. Turn off the instrument power supply.
2. Pull out all test leads from the input jacks.
3. Loosen the screw securing the battery cover with a screwdriver.
4. Remove the battery cover.
5. Remove old batteries.
6. Replace with new 2×1.5V AAA batteries.
7. Put the battery cover on and tighten the screws.

4.2. Initial Zero Adjustment

Before use, check whether the pointer points to the mechanical zero position. If it does not, turn the "pointer to zero" adjustment on the cover to align the pointer with zero.

5. Operating Instructions

Always ensure the test leads are properly connected and the rotary switch is set to the correct function and range before making any measurements.

5.1. DC Voltage Measurement (DCV)

1. Insert the black test lead into the "COM" jack and the red test lead into the "VΩmA" jack. For voltages greater than 1000V, use the 2500V jack.
2. Set the rotary switch to the "DCV" range.
3. Connect the test leads to the load or signal source under test.
4. If the voltage range is unknown, start with the highest range and decrease step-by-step.

5.2. AC Voltage Measurement (ACV)

1. Insert the black test lead into the "COM" jack and the red test lead into the "VΩmA" jack. For voltages greater than 1000V, use the 2500V jack.
2. Set the rotary switch to the "ACV" range.
3. Connect the test leads to the load or signal source under test.

5.3. Direct Current Measurement (DCA)

1. Insert the black test lead into the "COM" jack and the red test lead into the "VΩmA" jack. For currents greater than 500mA, use the "10A" jack.
2. Set the rotary switch to the "DCA" range.
3. Connect the test leads in series with the circuit under test.
4. If the current range is unknown, start with the highest range and decrease step-by-step.

5.4. Alternating Current Measurement (ACA) (N version only)

1. Insert the black test lead into the "COM" jack and the red test lead into the "VΩmA" jack. For currents greater than 500mA, use the "10A" jack.
2. Set the rotary switch to the "ACA" range.
3. Connect the test leads in series with the circuit under test.

5.5. Resistance Measurement (Ω)

1. Insert the black test lead into the "COM" jack and the red test lead into the "VΩmA" jack.
2. Set the rotary switch to the "Ω" range.
3. Connect the test leads to the resistance to be tested.
4. Note: Ensure the power supply to the circuit is cut off and any capacitors are discharged before measuring.

5.6. Capacitance Measurement (C) (N model only)

1. Set the rotary switch to the "C" range.
2. Insert the black test lead into the "COM" jack and the red test lead into the "VΩmA" jack.
3. Connect the measured capacitor to both ends of the test leads (red is positive). Pay attention to polarity.
4. Note: The capacitor must be completely discharged before each measurement to avoid errors.

5.7. Frequency Measurement (Hz) (N model only)

1. Insert the black test lead into the "COM" jack and the red test lead into the "VΩmA" jack.
2. Set the rotary switch to the "Hz" range.
3. Connect the test leads to the frequency source (VPP>1V).

5.8. Transistor hFE Parameter Measurement

1. Set the rotary switch to "hFE" (resistance × 10 gears).
2. Determine if the transistor is PNP or NPN.
3. Insert the three pins (E, B, C) of the transistor into the corresponding test sockets on the panel. The pointer deflection indicates the transistor's DC amplification factor hFE.
4. Note: If the pointer deflection is greater than 1000, check for incorrect pin insertion or a damaged transistor.

5.9. Diode Measurement (N model only)

1. Insert the black test lead into the "COM" jack and the red test lead into the "VΩmA" jack (black is positive).
2. Set the rotary switch to the "+" range. The pointer will deflect to full-scale.
3. Connect the test leads to the diode under test. The forward conduction pointer indicates the conduction voltage.

5.10. LED/Voltage Regulator Tube Measurement (L model only)

1. Set the rotary switch to the "+" position. The pointer will deviate to the right near full scale.
2. Connect the red test lead (output voltage "+") to the component.
3. Forward measurement indicates forward voltage drop. Reverse measurement indicates Zener tube steady voltage.

5.11. Buzzer Continuity Test

1. Insert the black test lead into the "COM" jack and the red test lead into the "VΩmA" jack.
2. Set the rotary switch to the ")))" range.
3. Connect the test leads to both ends of the circuit to be checked.
4. If the resistance is less than 30Ω (A/B/C/L type) or 15Ω (N type), the buzzer will beep.
5. Note: Ensure the circuit under test is powered off.

5.12. Infrared Remote Control Emission Signal Detection

This function helps determine if an infrared remote control transmitter is working normally.

1. Adjust the rotary switch to the infrared detection position.
2. Align the transmitter head of the remote control vertically with the infrared receiver window (deviation < ±15°).
3. Press the remote control launch button. If the red indicator light flashes, the transmitter is working normally.

5.13. Live Wire Identification (LIVE) (B model only)

1. Insert the red test lead into the "VΩmA" jack and the black test lead into the "COM" jack.
2. When the red test pen is connected to a live wire, the red indicator light will illuminate.

5.14. Battery Power Detection (BATT)

1. Insert the black test lead into the "COM" jack and the red test lead into the "VΩmA" jack.
2. Set the rotary switch to the "BATT" position.
3. Connect the test leads to the battery, observing correct polarity.
4. Observe the scale corresponding to BATT on the dial. Red indicates low or damaged battery; green indicates an intact battery.

5.15. Standard Resistance Box Application (A/B/C/L only)

The meter can be used as a standard resistance by utilizing the DC voltage or current range. For example, the 2.5V range in DC voltage is equivalent to a 50k standard resistance (2.5V×20k/V=50k). Refer to the technical specifications for other ranges. Avoid overloading when using this function.

6. Maintenance

6.1. General Maintenance

• Before opening the instrument case or removing the battery cover, ensure test leads are pulled out.
• Only specified replacement parts must be used for servicing.
• Before turning on the meter, cut off all relevant power supplies and ensure no static electricity is present.
• Calibration and maintenance should only be performed by professionals.
• When opening the meter case, be aware that some capacitors may hold dangerous voltages even after power-off.
• If any abnormality is observed, take the meter out of service immediately and send for repair.
• When not in use for a long time, remove the battery and store the meter in a place with low temperature and humidity.
• To clean the meter case, use a damp cloth and a small amount of detergent. Do not use abrasives or chemical solvents.
• Keep input sockets clean and dry to prevent oxidation of metal surfaces, which can affect readings.

7. Troubleshooting

• Unstable or Large Errors in Readings: The meter may be used near equipment with significant electromagnetic interference. Move to an area with less interference.
• Pointer Not at Zero: Adjust the "pointer to zero" knob on the cover.
• Resistance Scale Adjustment Less Than Zero: The battery is exhausted. Replace the AAA batteries immediately.
• Fuse Blown (for current measurements): Replace the fuse with one of the same specification.
• Self-Recovery Fuse Activated: Wait 30 seconds for the fuse to cool down before measuring again.
• Pointer Exceeds Maximum Scale: The measured value has exceeded the selected range. Adjust the gear rotary switch to a higher range.
• No Reading/Meter Not Functioning: Check battery installation and ensure batteries are not depleted. Verify test leads are properly connected.

8. Specifications

8.1. General Specifications

• Model: 88A
• Circuit Board: Double-sided gold-plated PCB
• Header: Internal magnet
• Power Supply: AAA*2 batteries (not included)
• Body Weight: Approx. 400g (excluding battery)
• Body Dimensions: 179mm (L) × 118mm (W) × 50mm (H)
• Operating Environment: 0~40°C (<80%RH)
• Storage Environment: -10~60°C (<70%RH; remove battery)
• Maximum Voltage: AC and DC 2500V between measuring terminal and earth

8.2. Measurement Ranges & Accuracy (Model N)

8.3. Measurement Ranges & Accuracy (Models A/B/C/L)

9. User Tips

• Power Saving: When the analog multimeter is not in use, always set it to a voltage range. The resistance range consumes power, so switching to a voltage range helps conserve battery life.
• Battery-Free Operation: If you only need to measure AC/DC voltage and DC current (without resistance), you can use the multimeter without installing batteries.

10. Warranty and Support

The accuracy of this instrument is guaranteed for one year from the date of delivery, under reference conditions (ambient temperature 18°C to 28°C, relative humidity not greater than 80%).

For detailed information, including comprehensive diagrams and troubleshooting guides, please refer to the official user manual PDF: View User Manual (PDF).

For further assistance or technical support, please contact your retailer or the manufacturer directly.