Current Testing Accessories for Multimeters
Current Testing Accessories for Multimeters
There are times when the current you need to measure exceeds the multimeter's range, or field conditions prevent you from opening the circuit to take a measurement. For high-current tests (typically above 2A) where high precision is not required, current clamps are extremely convenient. They wrap around a wire to measure current and convert it into a value the digital meter can process.
There are two basic types of current probes:
Current transformer (CT) type: Used exclusively for AC measurements.
Hall effect type: Capable of measuring both AC and DC current.
1. Current Transformer (CT) Probes
Typically use a 1mA:1A conversion ratio (e.g., 100A of current is converted to 100mA for easy measurement by a digital multimeter).
Connect the test leads to the "mA" and "Com" jacks on the multimeter.
Set the function selector to the AC milliamperes (mA) range.
2. Hall Effect Probes
Use a 1mV:1A conversion ratio for both AC and DC (e.g., 100A of AC current is converted to 100mV AC voltage).
Connect the test leads to the "V" and "Com" jacks.
Set the function selector to the voltage (V or mV) range. The multimeter will display 1mV to represent 1A of current.
Key Safety Precautions
Always disconnect power to the circuit before breaking it open or desoldering components for current measurement-even small currents can pose risks.
Never test voltage with the test leads plugged into the current measurement jacks; this can damage the meter or cause personal injury.
Example Models
CT-type current probe (e.g., Fluke 80i-400): The digital multimeter displays 1mA to represent 1A of actual current.
Hall effect probe (e.g., Fluke I-1010): Designed for high AC/DC current measurements, it converts current to a voltage signal where 1mV on the display equals 1A of actual current.
