2.1 Magnitude

CAL_M_Ix (x = A, B, C, N) and CAL_M_Vx (x = A, B, C, D) are used to calibrate the current and voltage magnitudes of phase x. Calibration may be iterative, using prior or old magnitude calibration factors to perform the next calibration cycle, or they may be set to 0x20000000 (unity) by the application prior to calibration.

The following formulas are used to calibrate the magnitude of phase x:

Where,

• x = [A, B, C, N] for CAL_M_Ix and x = [A, B, C, D] for CAL_M_Vx, and:

• Ix_RMS_IN is the input test current, with units [A]
• Vx_RMS_IN is the input test voltage, with units of [V]
• K_Ix is the current conversion factor in uQ22.10
• K_Vx is the voltage conversion factor in uQ22.10
• N is the number of samples in the integration period
• ACC_I_x is the accumulated all harmonics current quantity
• ACC_V_x is the accumulated all harmonics voltage quantity

Example:

An integration period of 1 second is used to gather the following accumulator values calibrate phase-A, with conditions: 120V, 50A, with the old calibrations set to unity (1.0000 = 0x20000000 [sQ2.29]).

• K_IA = 0x9A522 [uQ22.10] = 617.283
• K_VA = 0x19CC00 [uQ22.10] = 1651
• N = 4000 (number of samples in integration period)
• ACC_I_A = 0x1AF61FD09BBD = 29644398042045
• ACC_V_A = 0x144B58A21387 = 22313842119559