In this post, we will explore the six fundamental functions that a multimeter used by air conditioning technicians must have. Before delving into the functions, it is essential to highlight the two main types of digital multimeters available on the market.
Types of Digital Multimeters
- Manual Range Multimeter In this type of multimeter, besides selecting the required function, it is necessary to choose the correct range to obtain an accurate measurement. This type of multimeter is usually more affordable compared to automatic models.
- Auto-Range Multimeter This type of multimeter simplifies the measurement process, as it only requires selecting the desired function. The multimeter automatically adjusts to the appropriate range and provides an accurate reading.
Below, we describe the six essential functions that a multimeter must have for an air conditioning technician.
1. AC Voltage Measurement
This function is essential to verify whether the equipment is receiving the correct voltage supply. Locate the alternating current (AC) voltage supply from the external power grid, which is commonly 120 V or 220 V.
- Acceptable voltage variations in the power grid are typically within the range of ±5% of the nominal value. For example, for a 120 V grid, a variation between 114 V and 126 V is considered acceptable.
2. Amperage Measurement
To measure amperage, the digital multimeter must have a clamp meter function.
- Select the AC amperage option.
- Place a single power cable inside the clamp ring and measure the consumption.
- The measured value should be equal to or less than the equipment’s RLA (Rated Load Amperage).
3. Resistance Measurement
The resistance measurement function is primarily used in the kilohm (kΩ) scale to measure the resistance of temperature sensors.
- Turn off the equipment and disconnect it from the power supply if possible.
- With the sensor disconnected, set the multimeter to the kilohm scale and measure the sensor’s resistance.
- The value should not be zero or infinite. Additionally, the value should decrease when the sensor is heated by hand.
Another important application of this function is measuring the coil resistance of motors, whether from compressors or fans.
- In manual range multimeters, select a lower scale value.
- The resistance measurement between the coil pins should never be infinite.
- In inverter motors, resistance measurements between pins should be practically equal.
4. Continuity Function
The continuity function checks whether a cable is not broken and whether the signal or current can pass through without issues.
- Disconnect the equipment from the power supply before performing continuity measurements.
- If the circuit is closed and the cable is undamaged, the multimeter will emit a beep or display a value close to zero.
5. Capacitance Function
Capacitance measurement is essential to verify the condition of capacitors in different parts of the air conditioning system, such as the electronic board, the indoor unit fan motor, the outdoor unit, or the compressor.
- Set the multimeter to the appropriate capacitance scale.
- Ensure that the multimeter includes the most common capacitance ranges used in refrigeration and air conditioning equipment.
- Remember that capacitors store energy, so discharge the capacitor using a resistor before measuring its capacitance.
- Place the multimeter probes on the capacitor’s terminals and compare the measured value with the original value indicated on the component.
6. Temperature Measurement
Many multimeters include a temperature measurement function using a special sensor that connects to the multimeter.
- Place the sensor at the point you want to measure.
- This function is very useful for checking temperatures in various parts of the system, such as air ducts or compressors.
Conclusion
The multimeter is an indispensable tool for air conditioning technicians. The six functions mentioned above are essential for diagnosing and ensuring the proper functioning of refrigeration and air conditioning systems. Make sure to have a suitable multimeter that includes all these functions to facilitate your work and guarantee accurate results.
