What device is used to generate a precise reference signal for loop calibration?

• A. Multimeter
• B. Oscilloscope
• C. Precision calibrator or loop calibrator
• D. Thermometer

Answer: (C)

Calibration of loop signals requires a stable, known reference that can be injected into the loop to simulate a sensor and verify the transmitter and controller responses. A precision calibrator, also called a loop calibrator, is specifically designed to source and measure precise loop current (and sometimes voltage) with high accuracy. This lets you inject exact values like 4 mA, 12 mA, or other setpoints and confirm the loop’s behavior, accuracy, and linearity under test conditions. In contrast, a multimeter mainly measures and isn’t a precise source for loop signals; an oscilloscope visualizes waveforms but doesn’t inherently provide a trusted reference signal for calibration; a thermometer isn’t relevant to electrical loop calibration. So, the device built for generating a precise reference signal for loop calibration is the precision calibrator or loop calibrator.