Mestek CM87C Digital Clamp Meter User Manual

1. Introduction

The MESTEK CM87C is a professional digital clamp meter designed for accurate and reliable measurement of AC/DC current, AC/DC voltage, resistance, capacitance, frequency, and temperature. It features automatic ranging, True-RMS capabilities, inrush current measurement, VFD (Variable Frequency Drive) measurement, NCV (Non-Contact Voltage) detection, and LIVE wire recognition, making it an essential tool for electricians, maintenance personnel, and DIY enthusiasts.

This manual provides detailed instructions for the safe and effective use of your CM87C Digital Clamp Meter. Please read it thoroughly before operation and keep it for future reference.

2. Safety Information

Always adhere to basic safety precautions when using this instrument to avoid electric shock, injury, or damage to the meter or equipment under test.

• Do not exceed the maximum input values for any function.
• Ensure the test leads are properly connected and the function switch is in the correct position before making any measurement.
• Do not use the meter if it appears damaged or if the insulation on the test leads is compromised.
• Exercise extreme caution when working with live circuits.
• Always disconnect power to the circuit and discharge high-voltage capacitors before measuring resistance, capacitance, or continuity.
• Replace batteries immediately when the low battery indicator appears.

3. Product Overview

3.1. Package Contents

Upon unpacking, please verify that all items listed below are present and undamaged. If any items are missing or damaged, contact your supplier immediately.

Video: Unboxing the Mestek Digital Clamp Meter, showing the meter, test leads, K-type thermocouple, and user manual.

Image: Components included in the Mestek CM87C package.

• 1 x Clamp Meter (CM87C)
• 1 x K-type Thermocouple
• 1 x User Manual
• 1 x Pair of Test Probes (Red and Black)
• 1 x Instrument Storage Bag
• 1 x Packaging Box

3.2. Meter Layout

Image: Labeled diagram of the CM87C clamp meter showing its various parts and controls.

The meter features a large LCD display, a rotary function knob, and several function keys for various measurements and settings. Key components include:

• NCV Sensing Area: For non-contact voltage detection.
• Current Sensing Zone: The clamp jaw for current measurements.
• LED Lamp: For illumination.
• Flashlight/Data Hold Key: Activates flashlight and holds data.
• Trigger: Opens the clamp jaw.
• Function Knob: Selects measurement modes.
• Function Switch Key (SEL): Toggles between functions within a mode (e.g., AC/DC, Celsius/Fahrenheit).
• VFD/INRUSH Key: Activates VFD and Inrush current measurement modes.
• Backlight/ZERO Key: Activates backlight and performs DC current zeroing.
• Max/Min Switching Key: Records maximum and minimum values.
• Display: LCD screen showing measurement readings.
• COM & INPUT Terminals: For connecting test probes.

3.3. Battery Installation

The meter requires 2 x 1.5V AAA batteries. To install or replace batteries:

1. Ensure the meter is turned OFF.
2. Locate the battery compartment cover on the back of the meter.
3. Use a screwdriver to open the battery compartment.
4. Insert the batteries, observing the correct polarity (+ and -).
5. Replace the battery compartment cover and secure it with the screw.

4. Operating Instructions

4.1. Connecting Test Leads and Probes

• For voltage, resistance, capacitance, diode, and continuity measurements, insert the black test lead into the 'COM' terminal and the red test lead into the 'INPUT' terminal.
• For temperature measurements, connect the K-type thermocouple to the designated terminals, ensuring correct polarity.

4.2. Measurement Functions

Rotate the function knob to select the desired measurement mode.

4.2.1. AC/DC Current Measurement

This meter can measure both AC and DC current up to 600A using the clamp jaw.

Image: Measuring AC current with the clamp meter.

Image: Measuring DC current with the clamp meter.

1. Turn the function knob to the 'A~' (AC Current) or 'A=' (DC Current) position.
2. Press the trigger to open the clamp jaw.
3. Place a single wire of the circuit to be measured within the center of the clamp jaw. Ensure the jaw is fully closed.
4. Read the current value on the display.
5. For DC current, long press the 'ZERO' key to eliminate base numbers caused by magnetic field interference for more accurate results.

Image: DC current reset to zero function.

4.2.2. AC/DC Voltage Measurement

The meter can measure AC and DC voltage up to 600V.

Image: Measuring AC voltage with test leads.

Image: Measuring DC voltage with test leads.

1. Turn the function knob to the 'V~' (AC Voltage) or 'V=' (DC Voltage) position. The meter also features AUTO-VLOZ for automatic AC/DC voltage recognition.
2. Connect the test leads in parallel to the circuit or component under test.
3. Read the voltage value on the display.

Image: Automatic recognition of AC/DC voltage (AUTO-VLOZ).

4.2.3. Resistance Measurement

1. Turn the function knob to the 'Ω' (Resistance) position.
2. Ensure the circuit is de-energized and all capacitors are discharged.
3. Connect the test leads across the component to be measured.
4. Read the resistance value on the display.

Image: Measuring resistance.

4.2.4. Capacitance Measurement

1. Turn the function knob to the 'F' (Capacitance) position.
2. Ensure the capacitor is fully discharged before measurement.
3. Connect the test leads across the capacitor terminals.
4. Read the capacitance value on the display.

Image: Measuring capacitance.

4.2.5. Frequency Measurement

1. Turn the function knob to the 'Hz%' (Frequency) position.
2. Connect the test leads to the signal source.
3. Read the frequency value (Hz) and percentage (%) on the display.

Image: Measuring frequency.

4.2.6. Temperature Measurement

1. Turn the function knob to the '°C/°F' (Temperature) position.
2. Connect the K-type thermocouple to the meter's input terminals.
3. Place the thermocouple probe in contact with the object or liquid to be measured.
4. Briefly press the 'SEL' key to switch between Celsius (°C) and Fahrenheit (°F).
5. Read the temperature value on the display.

Image: Contact temperature measurement using K-type probe.

4.2.7. Diode Test

1. Turn the function knob to the Diode/Continuity position.
2. Press 'SEL' to select Diode test.
3. Connect the red test lead to the anode and the black test lead to the cathode of the diode.
4. Read the forward voltage drop on the display. Reverse the leads to check for open circuit.

Image: Diode test.

4.2.8. Continuity Test

1. Turn the function knob to the Diode/Continuity position.
2. Press 'SEL' to select Continuity test (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.

Image: Continuity test.

4.2.9. NCV (Non-Contact Voltage) Detection

The NCV function allows detection of AC voltage without direct contact.

Image: Non-contact AC voltage detection (Low Voltage / High Voltage).

1. Turn the function knob to the 'NCV' position.
2. Bring the NCV sensing area of the instrument close to the circuit or conductor.
3. The meter will sound different alarm prompts and the screen will display red, indicating the voltage intensity (L for Low, H for High).

4.2.10. LIVE Wire Recognition

This function helps identify live wires.

Image: Live Fire Line Recognition.

1. Turn the function knob to the 'LIVE' position.
2. Use a single test probe to touch the tested conductor.
3. If it's a live wire, the red backlight will illuminate, and the buzzer will sound an alarm.

4.2.11. Inrush Current Measurement

Measure the peak current when a machine is started.

Image: Surge current measurement (Inrush).

1. In AC current mode, press and hold the 'INRUSH' button to measure.
2. Before measuring, disconnect the load power supply.

4.2.12. VFD (Variable Frequency Drive) Measurement

Enabling VFD in AC voltage and current mode can effectively reduce interference from high-frequency signals on measurement results, displaying a more accurate voltage value of the measured line.

1. In AC Voltage or AC Current mode, press the 'VFD' button to activate the VFD function.
2. Proceed with your measurement as usual.

4.3. Special Functions

4.3.1. Data Hold

Short press the 'HOLD' key to lock the current measurement data on the display. The buzzer will sound a warning every 2 seconds to remind you that you are in a locked state. Press again to release.

Image: HOLD data lock function.

4.3.2. MIN/MAX Measurement

In AC/DC voltage or AC/DC current mode, press the 'MIN/MAX' key to record the minimum and maximum values. Press again to cycle through MAX, MIN, and current readings.

Image: MAX/MIN measurement.

4.3.3. Backlight and Flashlight

Short press the 'Backlight' key to turn on/off the display backlight. Long press the 'Flashlight' key to activate the LED flashlight.

Image: Flashlight and screen backlight in use.

4.3.4. Auto Power Off

The meter will automatically power off after approximately 15 minutes of inactivity to conserve battery life. Press any button or rotate the function knob to wake it up.

5. Maintenance

5.1. Cleaning

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

5.2. Battery Replacement

When the low battery indication (less than 2.4V) appears on the display, replace the batteries as described in Section 3.3. Prompt battery replacement ensures accurate readings and proper meter function.

5.3. Storage

If the meter is not used for an extended period, remove the batteries to prevent leakage and damage. Store the meter in its protective bag in a cool, dry place, away from direct sunlight and extreme temperatures.

6. Troubleshooting

If the meter does not function correctly, check the following:

• No display or dim display: Check battery level and replace if necessary.
• Incorrect readings: Ensure the correct function is selected, test leads are properly connected, and the circuit is de-energized for resistance/capacitance. For current, ensure only one wire is in the clamp.
• 'OL' or '-OL' on display: Indicates an over-range condition. The measured value exceeds the meter's maximum range for the selected function.
• Meter does not respond: Try turning the meter off and on again. If the issue persists, remove and reinsert the batteries.

For persistent issues, contact customer support.

7. Specifications

Image: Technical parameters of the CM87C.

Image: Detailed parameter comparison for CM87A, CM87B, and CM87C models.

8. User Tips

• For current measurements, always ensure the clamp jaw is fully closed around a single conductor. Measuring multiple conductors carrying current in opposite directions will result in a zero reading.
• When measuring DC current, use the 'ZERO' function to compensate for any residual magnetic fields, especially in environments with strong electromagnetic interference.
• Utilize the 'HOLD' function to freeze readings on the display when working in dimly lit areas or awkward positions where direct viewing is difficult.
• The NCV and LIVE wire recognition functions are excellent for quickly identifying live circuits and ensuring safety before proceeding with contact measurements.
• Keep the meter and accessories clean and dry to prolong their lifespan and maintain accuracy.

9. Warranty and Support

MESTEK products are designed for reliability and performance. This product is covered by a standard manufacturer's warranty against defects in materials and workmanship. Please refer to the warranty card included in your package for specific terms and conditions.

For technical support, troubleshooting assistance, or warranty claims, please contact the MESTEK Official Store or your authorized dealer. Keep your purchase receipt as proof of purchase.