Chapter 3
SLAU587 – August 2014
Calibration Techniques
3.1
Introduction
The EVM is programmed with statistical calibration values that allow the EVM to measure and give
roughly accurate readings; however the EVM has not been calibrated while shipped. To maximize
accuracy and to compensate component and manufacturing tolerance it is necessary for the EVM to go
through a calibration process. In this chapter the calibration techniques, required instruments, procedure
and steps of calibration will be discussed.
3.2
Calibration Techniques
The calibration of the EVM is defined based on the front-end interface model as shown in
.
Figure 3-1. Front-End Interface Model
For the current design a 2 point calibration and characterization is required. VGAIN, IGAIN, PGAIN, CAP,
RES, VDC_OFFSET, IDC_OFFSET are parameters that will be calibrated during the process; an
estimated value is put into the memory during design/characterization to help to speed up calibration.
(Note : Default CAP and RES should set to 0 before calibration).
VAC_OFFSET, IAC_OFFSET, PHASE_CORRECT are parameters that may not need calibration but a
characterization would be sufficient for embedded metering application except for high accuracy of <
0.1%.
NOTE:
The calibration values are written in one flash page in the EVM. Therefore, when a new
value needs to be written, the whole page is erased. The provided GUI performs the read,
modify, and write operation automatically. If a custom calibration method is implemented, the
application must read the complete set of calibration values, update the modified fields, and
write the complete set back to the EVM.
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SLAU587 – August 2014
Calibration Techniques
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