MESTEK CM85C Digital Clamp Meter Instruction Manual

1. Important Safety Information

Please read and understand all safety information and operating instructions before using this MESTEK CM85C Digital Clamp Meter. Failure to follow these instructions may result in electric shock, fire, or serious injury.

• This device complies with IEC 61010-1, CAT III 600V safety standards. Always adhere to these safety ratings.
• All measurement ranges are equipped with overload protection. However, do not exceed the maximum input values specified for each function.
• Before each use, inspect the test leads for any damage. Do not use if insulation is cracked or if the connectors are exposed.
• Do not apply more than the rated voltage, as marked on the meter, between the terminals or between any terminal and earth ground.
• Use caution when working with voltages above 30V AC RMS, 42V peak, or 60V DC. These voltages pose a shock hazard.
• Always ensure the meter is set to the correct function and range before making a measurement.
• When measuring current with the clamp, ensure only one conductor is enclosed within the clamp jaws.
• The Non-Contact Voltage (NCV) test can detect voltage without direct contact, reducing the risk of electric shock.
• Replace batteries immediately when the low battery indicator appears to ensure accurate readings.

2. Product Overview

The MESTEK CM85C is a compact, auto-ranging digital clamp meter designed for precise electrical measurements in various applications, including automotive and household electrical maintenance. It features True-RMS measurement for accurate readings on non-sinusoidal waveforms.

Key Features:

• Measures AC/DC Voltage up to 600V.
• Measures AC/DC Current up to 100A via clamp.
• Resistance, Capacitance, Frequency, Diode, and Continuity tests.
• Temperature measurement with included thermocouple (in Celsius and Fahrenheit).
• Non-Contact Voltage (NCV) detection for enhanced safety.
• True-RMS 1999 count display for accurate measurements.
• Auto-ranging for simplified operation.
• Data Hold function to freeze readings.
• DC current zeroing function (Z key).
• Backlight for visibility in low-light conditions.
• Automatic power-off after 10 minutes of inactivity to conserve battery.
• Low battery indicator.

Figure 2.1: MESTEK CM85C Clamp Meter with labeled components and dimensions (165mm height, 56mm width, 31mm depth). Key parts include NCV Induction Probe, AC/DC current sensing jaws, Feature selection dial, HD display, ZERO button, Backlight/HOLD button, and Function selection button.

3. What's in the Box

Upon opening the package, please verify that all the following items are included:

• MESTEK CM85C Digital Clamp Meter
• AAA Batteries (x2)
• Test Leads (red and black)
• K-Type Thermocouple Temperature Probe
• Cloth Carrying Bag
• User Manual

Figure 3.1: Included components of the MESTEK CM85C Clamp Meter kit.

4. Setup

4.1 Battery Installation

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

4.2 Connecting Test Leads

For most voltage, resistance, capacitance, diode, continuity, frequency, and temperature measurements, test leads are required.

• Insert the black test lead into the COM (Common) input jack.
• Insert the red test lead into the INPUT jack.

5. Operation

The MESTEK CM85C features a rotary dial for function selection and dedicated buttons for additional features.

5.1 Function Selection

Turn the rotary dial to select the desired measurement function. The meter will automatically select the appropriate range (auto-ranging) for most functions.

Figure 5.1: Examples of the CM85C performing battery voltage, AC voltage, capacitance, and resistance measurements.

5.2 AC/DC Voltage Measurement (V~)

1. Set the rotary dial to the V~ position.
2. Connect the test leads in parallel to the circuit or component under test.
3. Read the voltage value on the display. The meter will automatically detect AC or DC voltage.

Figure 5.2: Measuring DC voltage on a car battery using the test leads.

5.3 AC/DC Current Measurement (A~, A=)

This function uses the clamp jaws to measure current without breaking the circuit.

1. Set the rotary dial to the A~ or A= position (for AC or DC current respectively).
2. Press the clamp trigger to open the jaws.
3. Enclose only one single conductor within the clamp jaws. Do not clamp around multiple wires, as this will result in an inaccurate reading.
4. For DC current measurements, press the Z (Zero) button before clamping to eliminate any residual magnetic field and ensure accurate readings.
5. Read the current value on the display.

Figure 5.3: Top image shows DC current measurement on a car battery cable. Bottom image shows AC current measurement on a household electrical wire.

Figure 5.4: DC current measurement using the clamp function, highlighting the 25mm maximum jaw opening.

5.4 Resistance Measurement (Ω)

1. Set the rotary dial to the Ω position.
2. Ensure the circuit or component is de-energized before connecting the test leads.
3. Connect the test leads across the component to be measured.
4. Read the resistance value on the display.

5.5 Capacitance Measurement (∔)

1. Set the rotary dial to the ∔ position.
2. Ensure the capacitor is fully discharged before connecting the test leads.
3. Connect the test leads across the capacitor terminals.
4. Read the capacitance value on the display.

5.6 Diode Test (→|)

1. Set the rotary dial to the →| position.
2. Connect the red test lead to the anode and the black test lead to the cathode of the diode.
3. Read the forward voltage drop on the display. Reverse the leads to check for open circuit (OL) indication.

5.7 Continuity Test (•)))

1. Set the rotary dial to the •))) position.
2. Ensure the circuit or component is de-energized.
3. Connect the test leads across the circuit or component.
4. If the resistance is less than approximately 50Ω, the meter will emit an audible beep, indicating continuity.

5.8 Temperature Measurement (℃/℉)

1. Set the rotary dial to the ℃/℉ position.
2. Connect the K-type thermocouple probe to the INPUT and COM jacks, observing polarity.
3. Place the tip of the thermocouple on or in the object whose temperature is to be measured.
4. Read the temperature on the display. Press the SEL button to switch between Celsius (℃) and Fahrenheit (℉).

Figure 5.5: Measuring liquid temperature using the K-type thermocouple probe.

5.9 Non-Contact Voltage (NCV) Detection

The NCV function allows for safe detection of AC voltage without direct contact with live conductors.

1. Set the rotary dial to the NCV position.
2. Bring the top part of the meter (NCV sensor) close to the conductor or outlet you suspect has AC voltage.
3. The meter will emit an audible beep and the NCV indicator light will flash, indicating the presence of AC voltage.

Figure 5.6: NCV detection near an electrical outlet, indicated by flashing lights and an audible alert.

5.10 Data Hold (HOLD)

Press the H button to freeze the current reading on the display. Press it again to release the hold function.

5.11 Backlight

Press the backlight button (often integrated with the H button, indicated by a light icon) to turn the display backlight on or off. This improves visibility in dimly lit environments.

5.12 Auto Power Off

The meter will automatically power off after approximately 10 minutes of inactivity to conserve battery life. To reactivate, turn the rotary dial to OFF and then back to the desired function.

5.13 Low Battery Indicator

A battery symbol will appear on the display when the battery voltage is low. Replace the batteries promptly to ensure accurate measurements.

6. Maintenance

6.1 Cleaning

Wipe the meter casing with a damp cloth and mild detergent. Do not use abrasives or solvents. Ensure the meter is completely dry before use.

6.2 Battery Replacement

When the low battery indicator appears, replace the two AAA batteries as described in Section 4.1. Remove batteries if the meter will not be used for an extended period.

6.3 Storage

Store the meter in its cloth carrying bag in a cool, dry place, away from direct sunlight and extreme temperatures.

7. Troubleshooting

8. Specifications

• Display: 1999 Counts, True-RMS
• Jaw Opening: 25mm (Maximum)
• Overload Protection: Full-scale protection on all ranges
• Power Source: 2 x AAA Batteries
• Auto Power Off: Approximately 10 minutes of inactivity
• Dimensions: 16.5 x 5.6 x 3.1 cm
• Weight: 333 Grams
• Safety Rating: IEC 61010-1, CAT III 600V
• Certifications: CE, EMC, FCC, RoHS

9. Warranty Information

This MESTEK CM85C Digital Clamp Meter comes with a 2-year warranty from the date of purchase. This warranty covers defects in materials and workmanship under normal use.

The warranty does not cover damage caused by misuse, accident, unauthorized modification, neglect, or improper operation. For warranty claims or technical support, please contact MESTEK customer service through your original point of purchase or visit the official MESTEK website for contact details.