Major Tech MT870 True RMS Digital Multimeter

Introduction

The MT870 multimeter is a slim, portable, and robust digital multimeter designed with drop-proof capabilities. It features a 2000-count LCD monitor with large 25mm digits for clear and easy reading. The internal circuitry is based on large-scale IC A/D converters and includes an over-load protection circuit, providing excellent performance. This multimeter is ideal for various applications and can measure DC & AC True RMS voltage, DC & AC True RMS current, resistance, battery test, diode test, and audible continuity.

If the equipment is used in a manner not specified by the manufacturer, the protection provided may be impaired. This equipment conforms to UL STD. 61010-1, 61010-2-030, and 61010-2-033, and is certified to CSA STD. C22.2 NO. 61010-1, 61010-2-030, and 61010-2-033.

Panel Layout

The multimeter features the following controls and indicators:

1. LCD Display: A 3 1/2 digit LCD screen displaying measurements, function symbols, and indicators like "OL" for over-range and a low battery symbol.
2. SELECT Key: Used to select diode or continuity testing modes, or to switch between DC and AC for current measurements. Holding this key while powering on disables the Auto Power Off function.
3. RANGE Key: Toggles the multimeter between automatic and manual ranging modes. Pressing and holding for over 2 seconds returns to auto mode.
4. MAX/MIN Key: Locks and displays the maximum or minimum recorded measurement. The "MAX" or "MIN" indicator appears on the display. Pressing for over 2 seconds exits this mode.
5. D.HOLD Key: Locks the current displayed measurement value. The "DH" indicator appears on the display. Pressing again exits this mode.
6. RESET Key: Resets the multimeter's internal settings.
7. Rotary Switch: Used to select the desired measurement function (e.g., Voltage, Current, Resistance) and range.
8. COM Jack: The common (negative) input terminal, typically black.
9. 10A Jack: Input terminal for measuring high DC or AC current up to 10 Amperes.
10. VΩmA Jack: Input terminal for measuring voltage, resistance, and lower current ranges (μA, mA).
11. Meter Casing: The main housing of the digital multimeter.
12. Protective Casing: An outer protective layer or boot for durability and safety.

Safety Information

• The meter is designed according to IEC61010-1 for electronic measuring instruments with an over-voltage category of 600V (CAT II) or 300V (CAT III) and pollution degree 2.
• Follow all safety and operating instructions to ensure safe usage and maintain good operating condition.
• Safety Symbols:
  • [Important safety information]: Refer to the operating manual.
  • [Dangerous voltage]: Indicates the presence of hazardous voltage.
  • [Double insulation]: Indicates protection Class II construction.

Special Cautions for Operation

1. The meter is safe only when used according to standard procedures with the supplied test leads. Replace damaged test leads with those having identical electrical specifications.
2. To avoid the risk of electric shock, do not use the meter if the casing has been opened.
3. Ensure the range switch is set to the correct position before making a measurement.
4. To prevent electric shock and instrument damage, input signals must not exceed the specified limits.
5. When measuring TV sets or switched power supplies, be aware of potential pulses that could damage the circuitry.
6. Do not change the range switch position randomly during measurement.
7. Exercise caution when measuring voltages higher than DC 60V and AC 30V.
8. Replace the protection fuse only with the same type and specification.
9. Verify the multimeter's operation by measuring a known voltage.
10. After operation, set the function switch to "OFF" to conserve battery power.
11. If the meter will not be used for an extended period, remove the battery to prevent damage from battery leakage.

General Specifications

1. Max Voltage between input terminal and Earth Ground: CAT II 600V or CAT II 300V.
2. Over-range Indication: Displays "OL" for the significant digit.
3. Automatic display of negative polarity: "-" symbol.
4. Low Battery Indication: "[Low battery indicator]" displayed.
5. Display: 3 1/2 digit LCD with a maximum reading of 1999.
6. Auto range and manual range control.
7. Auto Power Off: The meter switches to standby mode if no key is pressed or the range is not changed for 15 minutes. Press any key to exit standby. To disable auto power off, press and hold the SELECT key during system restart.
8. Fuse protection: 250mA/600V Fast Fuse, 10A/600V Fast Fuse.
9. Power supply: 2 x 1.5V "AA" R6P batteries.
10. Operating Temperature: 0°C to 40°C (relative humidity <85%).
11. Storage Temperature: -10°C to 50°C (relative humidity <85%).
12. Guaranteed precision temperature: 23±5°C (relative humidity <70%).
13. Dimension: 150 x 100 x 36mm.
14. Weight: Approximately 250g (including battery).

Testing Specifications

Accuracy is specified for one year after calibration, at 18°C to 28°C (64°F to 82°F) with relative humidity up to 70%.

DC Voltage

* Impedance: 10MΩ. More than 100MΩ on 200mV range.

* Overload protection: 600V DC or AC rms.

AC Voltage

* AC True RMS.

* Impedance: 10MΩ.

* Overload protection: 600V DC or AC rms.

* Frequency Range: 40 to 2kHz.

DC Current

* Overload protection: 250mA/600V Fast Fuse; 10A/600V Fast Fuse, 10A up to 10 seconds.

AC Current

* AC True RMS.

* Overload protection: 250mA/600V Fast Fuse; 10A/600V Fast Fuse, 10A up to 10 seconds.

* Frequency Range: 40 to 2kHz.

Resistance

* Overload protection: 600V DC or AC rms.

Battery Test

* Overload protection: 250mA/600V Fast Fuse.

Diode and Audible Continuity Test

* Overload protection: 600V DC or AC rms.

Note: Ensure all power is removed and capacitors are discharged before performing these measurements.

Battery Replacement

1. When the battery voltage drops below the proper operating range, the "[Low battery indicator]" symbol will appear on the LCD, signaling the need for battery replacement.
2. Before replacing the battery, set the selector switch to "OFF" and remove the test leads from the terminals. Open the battery compartment cover using a suitable screwdriver.
3. Replace the old battery with the same type of battery (2 x 1.5V "AA" R6P).
4. Close the battery compartment cover and fasten the screw.

Fuse Replacement

1. This meter is equipped with a 250mA/600V fast fuse for protecting the battery test and current measuring circuits up to 200mA, and a 10A/600V fuse for the 10A range.
2. Ensure the meter is disconnected from any external circuit. Set the selector switch to "OFF" and remove the test leads. Open the battery compartment cover with a suitable screwdriver.
3. Replace the old fuse with one of the same type and rating: 6x32mm 250mA/600V fast fuse or 6x32mm 10A/600V fast fuse.
4. Close the battery compartment cover and fasten the screw.

Maintenance

1. Replace test leads if their insulation is broken or internal wires are exposed. Use only test leads with identical specifications.
2. Clean the meter using only a moist fabric or a small amount of mild detergent; avoid chemical solutions.
3. Do not operate the meter before the back cover is properly closed and secured with screws. If any issues arise, stop operation immediately and send the meter for maintenance.
4. Remove the battery if the meter will not be used for an extended period.

Accessories

1. Test Leads: Rated for 600V, 10A. Replacement leads must meet EN 61010-01 standard, rated CAT III 600V, 10A or better.
2. Operator's Manual: This document.