Mastech MS8250A Digital Multimeter User Manual

1. Introduction

This user manual provides detailed instructions for the safe and effective operation of the Mastech MS8250A Digital Multimeter. The MS8250A is a portable, battery-powered instrument designed for measuring AC/DC voltage, AC/DC current, resistance, capacitance, frequency, duty cycle, diode, and continuity. It also features non-contact voltage detection, data hold, and a display backlight.

Please read this manual thoroughly before using the device to ensure proper operation and to prevent potential hazards.

2. Safety Information

Always adhere to the following safety precautions to avoid personal injury or damage to the multimeter or the equipment under test.

• Read and understand all instructions in this manual before use.
• Do not exceed the maximum input values specified for each function.
• Never use the multimeter if its casing is damaged or if the test leads are frayed or broken.
• Ensure the function switch is in the correct position for the desired measurement before connecting the test leads.
• Use extreme caution when working with voltages above 30V AC RMS, 42V peak, or 60V DC. These voltages pose a shock hazard.
• The Mastech MS8250A is rated for CAT IV 600V. This rating indicates its suitability for measurements at the source of the low-voltage installation, such as electricity meters and primary overcurrent protection devices.
• Always disconnect the test leads from the circuit before changing the function switch position.
• Replace batteries immediately when the low battery indicator appears to ensure accurate readings.

3. Product Overview

3.1 Key Features

• Display: 4000 counts
• Auto Ranging and Manual Ranging capabilities
• Auto Power Off function to conserve battery life
• Relative Measurement mode
• Non-Contact Voltage (NCV) Detector
• Diode Open voltage: 1.5V
• Continuity Buzzer: Sounds when resistance is less than 50Ω ± 20Ω
• Data Hold function
• Low Battery Display indicator
• Display Backlight for visibility in low-light conditions

3.2 Multimeter Components

The Mastech MS8250A Digital Multimeter features a clear LCD display, a central rotary function switch, and multiple input jacks for test leads.

The main components include:

• LCD Display: Shows measurement readings, units, and various indicators.
• Function Buttons: Include FUNC (function select), RANGE (manual range), REL (relative measurement), HOLD (data hold), and backlight button.
• Rotary Switch: Used to select the desired measurement function (e.g., V∼, V−, Ω, A∼, A−, Diode, Continuity, NCV).
• Input Jacks:
• VΩHz%→←CAP: Input for voltage, resistance, frequency, capacitance, and diode/continuity measurements.
• mAµA: Input for milliampere and microampere current measurements.
• A: Input for ampere current measurements (up to 10A).
• COM: Common (ground) input for all measurements.
• NCV Sensor: Located at the top of the multimeter for non-contact voltage detection.

4. Setup

4.1 Battery Installation

The Mastech MS8250A requires two LR44 batteries for operation. These are typically included with the device.

1. Ensure the multimeter is turned OFF.
2. Locate the battery compartment cover on the back of the multimeter.
3. Use a screwdriver to loosen the screw(s) securing the battery cover.
4. Carefully remove the battery cover.
5. Insert two new LR44 batteries, observing the correct polarity (+ and -) as indicated inside the compartment.
6. Replace the battery cover and tighten the screw(s) securely.

Note: Always dispose of used batteries responsibly according to local regulations.

5. Operating Instructions

5.1 General Operation

• Power On/Off: Rotate the function switch from the 'OFF' position to any desired measurement function to turn the multimeter ON. Rotate it back to 'OFF' to power OFF.
• Auto Power Off: The multimeter will automatically power off after approximately 15 minutes of inactivity to save battery. Press any button or rotate the function switch to resume operation.
• Auto Ranging: By default, the multimeter operates in auto-ranging mode, automatically selecting the appropriate measurement range.
• Manual Ranging: Press the 'RANGE' button to switch to manual ranging. Each press will cycle through available ranges. Press and hold 'RANGE' to return to auto-ranging.
• Data Hold: Press the 'HOLD' button to freeze the current reading on the display. Press it again to release.
• Backlight: Press the backlight button (often indicated by a light bulb icon) to turn the display backlight ON or OFF.

5.2 Measurement Functions

Before any measurement, ensure the test leads are correctly inserted into the appropriate input jacks.

5.2.1 DC Voltage Measurement (V−)

1. Insert the red test lead into the 'VΩHz%→←CAP' jack and the black test lead into the 'COM' jack.
2. Rotate the function switch to the 'V−' position.
3. Connect the test leads in parallel to the DC voltage source or component to be measured.
4. Read the voltage value on the display. Observe polarity.

5.2.2 AC Voltage Measurement (V∼)

1. Insert the red test lead into the 'VΩHz%→←CAP' jack and the black test lead into the 'COM' jack.
2. Rotate the function switch to the 'V∼' position.
3. Connect the test leads in parallel to the AC voltage source or component to be measured.
4. Read the voltage value on the display.

5.2.3 DC Current Measurement (A−, mA−, µA−)

1. For µA/mA: Insert the red test lead into the 'mAµA' jack and the black test lead into the 'COM' jack.
2. For A: Insert the red test lead into the 'A' jack and the black test lead into the 'COM' jack.
3. Rotate the function switch to the appropriate 'A−', 'mA−', or 'µA−' position.
4. Connect the test leads in series with the circuit to be measured.
5. Read the current value on the display.

Caution: Never connect the multimeter in parallel when measuring current, as this can blow the fuse or damage the meter.

5.2.4 AC Current Measurement (A∼, mA∼, µA∼)

1. Follow the same lead connection steps as for DC Current Measurement.
2. Rotate the function switch to the appropriate 'A∼', 'mA∼', or 'µA∼' position.
3. Connect the test leads in series with the circuit to be measured.
4. Read the current value on the display.

5.2.5 Resistance Measurement (Ω)

1. Insert the red test lead into the 'VΩHz%→←CAP' jack and the black test lead into the 'COM' jack.
2. Rotate the function switch to the 'Ω' position.
3. Ensure the circuit or component is de-energized before measuring resistance.
4. Connect the test leads across the component to be measured.
5. Read the resistance value on the display.

5.2.6 Diode Test (→←)

1. Insert the red test lead into the 'VΩHz%→←CAP' jack and the black test lead into the 'COM' jack.
2. Rotate the function switch to the '→←' position.
3. Connect the red test lead to the anode and the black test lead to the cathode of the diode.
4. The display will show the forward voltage drop. Reverse the leads; the display should show 'OL' (Open Loop) for a good diode.

5.2.7 Continuity Test (→←)

1. Insert the red test lead into the 'VΩHz%→←CAP' jack and the black test lead into the 'COM' jack.
2. Rotate the function switch to the '→←' position and press the 'FUNC' button to select continuity mode (indicated by a buzzer icon).
3. Connect the test leads across the circuit or component.
4. If the resistance is below approximately 50Ω, the buzzer will sound, indicating continuity.

5.2.8 Non-Contact Voltage (NCV) Detection

1. Rotate the function switch to the 'NCV' position.
2. Move the top part of the multimeter (where the NCV sensor is located) close to the conductor being tested.
3. If AC voltage is detected, the multimeter will emit an audible beep and/or flash an indicator light. The intensity of the indication may vary with voltage strength.

5.2.9 Relative Measurement (REL)

1. Select the desired measurement function (e.g., voltage, resistance).
2. Take a reference measurement.
3. Press the 'REL' button. The display will show '0' and subsequent measurements will be displayed as a difference from the stored reference value.
4. Press 'REL' again to exit relative mode.

6. Specifications

The following table details the technical specifications for the Mastech MS8250A Digital Multimeter.

6.1 General Specifications

• Display: 4000 counts
• Power Source: 2 x LR44 batteries (included)
• Dimensions (L x W x H): 6.3 x 3.54 x 1.97 inches (160 x 90 x 50 mm)
• Weight: 1.1 Pounds (0.5 Kilograms)
• Safety Rating: CAT IV 600V

7. Maintenance

7.1 Cleaning

To clean the multimeter, wipe the case with a damp cloth and a mild detergent. Do not use abrasives or solvents. Ensure the device is completely dry before use.

7.2 Battery Replacement

When the low battery indicator appears on the display, replace the batteries as described in Section 4.1. Using the multimeter with low batteries may result in inaccurate readings.

7.3 Storage

If the multimeter is not to be used for an extended period, remove the batteries to prevent leakage and potential damage to the device. Store the multimeter in a cool, dry place, away from direct sunlight and extreme temperatures.

8. Troubleshooting

• No Display or Faint Display: Check battery installation and charge. Replace batteries if necessary.
• Incorrect Readings: Ensure the function switch is set to the correct measurement type and range. Verify test lead connections. Check battery level.
• 'OL' (Overload) Display: The measured value exceeds the selected range. Switch to a higher range or ensure the input is within the meter's maximum capabilities.
• No Continuity Beep: Ensure the function switch is in the continuity position and the 'FUNC' button has been pressed to select continuity mode. Check test leads for damage.

If problems persist, contact Mastech customer support or your local distributor for assistance.

9. Warranty and Support

For warranty information and technical support, please refer to the documentation provided with your purchase or visit the official Mastech website. You may also contact the seller directly for assistance.

For more information about Mastech products, visit the Mastech Store.