Mastech MS8268 Digital Multimeter

1. Introduction

This manual provides comprehensive instructions for the safe and effective operation of the Mastech MS8268 Digital AC/DC Auto/Manual Range Digital Multimeter. The MS8268 is a versatile instrument designed for precise electrical measurements, featuring a large LCD display, auto/manual ranging, and various measurement functions. Please read this manual thoroughly before use and retain it for future reference.

2. Safety Information

Always adhere to safety precautions when using the multimeter to prevent personal injury or damage to the device. This meter complies with IEC1010-1, CAT. III 600V & CAT. II 1000V safety standards.

• Do not exceed the maximum input values for any range.
• Exercise extreme caution when working with voltages above 30V AC RMS, 42V peak, or 60V DC. These voltages pose a shock hazard.
• Ensure the correct function and range are selected before making measurements.
• Always disconnect the test leads from the circuit before changing functions or ranges.
• The meter features full overload protection and a built-in resettable fuse for mA and uA ranges. The 10A range is protected by a F 10A/250V 6.3x32mm fuse.
• A misconnection alarm system and red lights indicate correct terminal usage, enhancing safety.
• Do not operate the meter if it appears damaged or if the case is open.
• Replace batteries immediately when the low battery indicator appears to ensure accurate readings.

3. Product Overview

3.1. Components and Controls

The Mastech MS8268 Digital Multimeter features a robust design with intuitive controls for various measurement tasks.

Figure 1: Front view of the Mastech MS8268 Digital Multimeter, showing the LCD display, rotary dial, and function buttons.

3.2. Display Features

• 3 3/4 Digital Large LCD: Provides a clear reading with 4000 counts.
• Backlight: Illuminates the display for visibility in low-light conditions. Activates by pressing the 'LIGHT' button.
• Unit Symbol Display: Shows the appropriate unit (e.g., V, A, Ω, Hz, F) for the selected measurement.
• Low Battery Indication: An icon appears when battery power is low, indicating the need for replacement.

3.3. Control Functions

• Rotary Dial: Used to select the desired measurement function (e.g., DCV, ACV, Resistance, Current, Capacitance, Frequency, Diode, Continuity, hFE).
• RANGE Button: Toggles between auto-ranging and manual ranging modes.
• SELECT Button: Used to switch between different measurement types within a single rotary dial position (e.g., AC/DC, Continuity/Diode, Frequency/Duty Cycle).
• HOLD Button: Freezes the current reading on the display. Press again to release.
• LIGHT Button: Activates the display backlight.
• REL Button: Activates the relative value measurement function.

4. Setup

4.1. Battery Installation

The multimeter requires three (3) 1.5V AAA batteries for operation. These are typically included.

1. Ensure the multimeter is turned OFF.
2. Locate the battery compartment cover on the back of the unit.
3. Unscrew the retaining screw(s) and remove the cover.
4. Insert the three AAA batteries, observing the correct polarity (+ and -) as indicated inside the compartment.
5. Replace the battery cover and secure it with the screw(s).

Figure 2: Rear view of the Mastech MS8268, showing the battery compartment with three AAA batteries installed.

4.2. Connecting Test Leads

Proper connection of test leads is crucial for accurate and safe measurements. The meter features red lights to indicate correct terminal usage.

1. Insert the black test lead into the 'COM' (Common) input jack.
2. For voltage, resistance, capacitance, frequency, diode, and continuity measurements, insert the red test lead into the 'VΩHz' input jack.
3. For current measurements (mA/uA), insert the red test lead into the 'mAΩA' input jack.
4. For high current measurements (10A), insert the red test lead into the '10A' input jack.
5. Ensure the leads are fully seated in the jacks.

Figure 3: The Mastech MS8268 Multimeter shown with its included test leads and multi-function socket.

5. Operating Instructions

The MS8268 offers both auto and manual ranging capabilities. In auto-ranging mode, the meter automatically selects the best range for the measurement. In manual mode, you can select the range using the 'RANGE' button.

5.1. DC Voltage Measurement (V–)

• Turn the rotary dial to the 'V–' position.
• Connect the red test lead to the positive (+) side of the circuit and the black test lead to the negative (-) side.
• Read the voltage value on the display.

5.2. AC Voltage Measurement (V∼)

• Turn the rotary dial to the 'V∼' position.
• Connect the test leads across the AC voltage source.
• Read the voltage value on the display.

5.3. Resistance Measurement (Ω)

• Turn the rotary dial to the 'Ω' position.
• Ensure the circuit is de-energized before measuring resistance.
• Connect the test leads across the component to be measured.
• Read the resistance value on the display.

5.4. DC Current Measurement (A–)

• Turn the rotary dial to the appropriate 'A–' range (uA, mA, or 10A).
• Connect the meter in series with the circuit. Ensure the red lead is in the correct current input jack (mA/uA or 10A).
• Read the current value on the display.

5.5. AC Current Measurement (A∼)

• Turn the rotary dial to the appropriate 'A∼' range (uA, mA, or 10A).
• Connect the meter in series with the circuit. Ensure the red lead is in the correct current input jack (mA/uA or 10A).
• Read the current value on the display.

5.6. Capacitance Measurement (F)

• Turn the rotary dial to the 'F' position.
• Discharge the capacitor before measurement.
• Connect the test leads across the capacitor.
• Read the capacitance value on the display.

5.7. Frequency Measurement (Hz)

• Turn the rotary dial to the 'Hz/%' position.
• Connect the test leads across the signal source.
• Read the frequency value on the display. Press 'SELECT' to toggle to Duty Cycle if needed.

5.8. Transistor hFE Measurement

• Turn the rotary dial to the 'hFE' position.
• Insert the transistor leads into the appropriate holes on the multi-function socket (NPN or PNP).
• Read the hFE value on the display.

5.9. Continuity Test (♫)

• Turn the rotary dial to the '♫/Diode' position.
• Press the 'SELECT' button until the continuity symbol (♫) appears.
• Connect the test leads across the circuit or component. An audible tone indicates continuity (resistance below approx. 50Ω).

5.10. Diode Test (▲)

• Turn the rotary dial to the '♫/Diode' position.
• Press the 'SELECT' button until the diode symbol (▲) appears.
• Connect the red lead to the anode and the black lead to the cathode of the diode.
• Read the forward voltage drop on the display. Reverse the leads to check for open circuit.

5.11. Relative Value Measurement (REL)

• Perform a measurement.
• Press the 'REL' button. The current reading becomes the reference value, and subsequent readings will be displayed as the difference from this reference.
• Press 'REL' again to exit relative mode.

5.12. Data Hold (HOLD)

• During any measurement, press the 'HOLD' button to freeze the current reading on the display.
• Press 'HOLD' again to release the reading and resume live measurement.

5.13. Auto Power Off

The meter features a 'Sleep mode' and will automatically power off after approximately 15 minutes of inactivity to conserve battery life. Press any button or turn the rotary dial to wake the meter.

6. Maintenance

6.1. Cleaning

Wipe the case with a damp cloth and mild detergent. Do not use abrasives or solvents. Keep the terminals free from dirt and moisture.

6.2. Battery Replacement

When the low battery indicator appears on the display, replace the three (3) 1.5V AAA batteries as described in Section 4.1. Prompt battery replacement ensures accurate readings and proper meter function.

6.3. Fuse Replacement

If the current measurement function fails, the fuse may need replacement. The mA and uA ranges are protected by a resettable fuse. The 10A range is protected by a F 10A/250V 6.3x32mm fuse.

1. Ensure the multimeter is turned OFF and test leads are disconnected.
2. Open the battery compartment cover as described in Section 4.1.
3. Locate the fuse(s) inside the compartment.
4. Carefully remove the old fuse and replace it with a new fuse of the identical type and rating (F 10A/250V 6.3x32mm for the 10A range).
5. Replace the battery cover and secure it.

7. Troubleshooting

• Display shows 'OL' or '1': This indicates an over-range condition or an open circuit. Check if the measured value exceeds the selected range or if the circuit is open.
• No display or faint display: Check battery installation and ensure batteries are not depleted. Replace batteries if necessary.
• Inaccurate readings: Ensure test leads are properly connected and not damaged. Verify the correct function and range are selected. Check battery level.
• Continuity test not beeping: Ensure the 'SELECT' button has been pressed to activate the continuity function (symbol ♫). Check if the circuit resistance is too high.
• Current measurement not working: Check if the fuse for the current range is blown and replace if necessary (refer to Section 6.3). Ensure the meter is connected in series with the circuit.
• Display fluctuates wildly when leads are not touching anything: This is normal behavior for digital multimeters, especially in voltage or resistance modes, and does not indicate a fault.

8. Specifications

9. Warranty and Customer Support

For information regarding warranty coverage, technical support, or service, please refer to the Mastech official website or contact your local distributor. Keep your purchase receipt as proof of purchase.