Manual Calibration

The calibration constants must be calculated according to the metrology library documentation. A spreadsheet is included in the distribution package to make the procedure easier. This spreadsheet calculates the proper values of the “CAL_x” registers and generates the commands to be sent to the board through the serial console to update the registers. This section explains how to calibrate the board using the spreadsheet. These are the steps to follow:

  1. Follow the instructions described in the previous chapter, ensuring that the board is properly configured, taking special attention with the configuration related to the hardware connected to the metrology inputs
  2. Open the METROLOGY_CONFIGURE_CALIBRATE_CALCULATE.xlsx spreadsheet, go to the "Step by step guide" sheet, and follow the steps.
    Note: The steps described here could change depending on the version of the Excel file.
  3. Configure the input sources and the meter tester if used (meter form, voltage, current, etc). In this example, a PIC32CXMTC board will be calibrated using a WECO tester, configured to generate 5A and 220V to each phase, at 60 Hz. Phase shift between voltage vectors is 120º, and phase shift between voltage and current vectors is 60º for each phase, but any convenient values of voltage, current and phase angle may be used.
  4. Write these values in the yellow cells.
    Figure 1-114. Input Sources Configuration
  5. If voltage-to-voltage phase correction is desired, write “1” in the yellow cells. If enabled, the metrology library will also correct the phase shift between the voltage vectors.
    Figure 1-115. Voltage-to-Voltage Phase Correction
  6. Select the channels to be calibrated.
    Figure 1-116. Channel Selection
  7. Set the calibration constants to the default values (unity gain and zero phase adjustments). To do that, copy the green and purple cells to the metrology console. The constants can be sent as groups using the "DCM" command:
    Figure 1-117. Set Default Values as Groups

    Or it can be sent one by one. This is useful if not all channels are being configured and just certain channels need to be set to the default values:

    Figure 1-118. Set Default Values Individually
  8. Energize the board, applying the established configuration (in the WECO software, this is done through the “JOG” command), and wait for the meter tester to stabilize the voltage and current sources.
  9. On PuTTy, enter the following commands: “PAR[U]”, “PAR[I]”, “PAR[A]”, “DCR”, “DSR” and “DAR”. Then, copy and paste the results to the blue cells:
    Figure 1-119. Read the Measured Parameters from the Board (Commands PAR)
    Figure 1-120. Read DSP_CONTROL Registers (Command DCR)
    Figure 1-121. Read DSP_ST Register (Command DSR)
    Figure 1-122. Read DSP_ACC Register (Command DAR)
  10. The spreadsheet calculates the calibration constants (”CAL_x” registers) and generates the commands to be sent to the board through the serial console. The user can choose between:
    1. Sending the calibration constants as groups using the”DCM” command; able to send multiple commands at the same time. To do that, copy the green and purple cells to the metrology console.
      Figure 1-123. Set Calibration Constants as Groups
    2. Sending the calibration constants one by one by using the “DCW” command. To do that, copy the green and purple cells to the metrology console.
      Figure 1-124. Set Calibration Constants Individually
  11. Read the control registers (command DCR) to check that the calibration registers were successfully updated (values in bold):
    DCR
00 STATE_CTRL      01 FEATURE_CTRL0   02 FEATURE_CTRL1   03 METER_TYPE
2                  300                0                  CCC
04 M               05 N_MAX           06 PULSE_CTRL0     07 PULSE_CTRL1
0                  1130               81009100           81029100
08 PULSE_CTRL2     09 P_K_T           10 Q_K_T           11 I_K_T
11049100           60000              500000             500000
12 CREEP_THR_P     13 CREEP_THR_Q     14 CREEP_THR_I     15 POWER_OS_CTRL
2E9A               2E9A               212D               700000
16 POWER_OFFSET_P  17 POWER_OFFSET_Q  18 SWELL_THR_VA    19 SWELL_THR_VB
0                  0                  5E84F61            5E84F61
20 SWELL_THR_VC    21 SAG_THR_VA      22 SAG_THR_VB      23 SAG_THR_VC
5E84F61            1A2EC26            1A2EC26            1A2EC26
24 K_IA            25 K_VA            26 K_IB            27 K_VB
9A523              19CC00             9A523              19CC00
28 K_IC            29 K_VC            30 K_IN            31 CAL_M_IA
9A523              19CC00             9A523              1FD81FE4
32 CAL_M_VA        33 CAL_M_IB        34 CAL_M_VB        35 CAL_M_IC
209B7735           1FD1E083           209E668E           1FDCDFE3
36 CAL_M_VC        37 CAL_M_IN        38 CAL_PH_IA       39 CAL_PH_VA
209EEBFD           20000000           FFED406E           0
40 CAL_PH_IB       41 CAL_PH_VB       42 CAL_PH_IC       43 CAL_PH_VC
FFF05E08           FFFE9C17           FFF0DCFD           FFFDCCAD
44 CAL_PH_IN       45 CAPTURE_CTRL    46 CAPT_BUFF_SIZE  47 CAPTURE_ADDR
0                  0                  1F40               20000534
48 RESERVED_C48    49 RESERVED_C49    50 RESERVED_C50    51 AT_CTRL_20_23
0                  0                  0                  1010103
52 AT_CTRL_24_27   53 AT_CTRL_28_2B   54 RESERVED_C54    55 POWER_OS_P_A
7000001            3                  0                  D96AAF3B
56 POWER_OS_P_B    57 POWER_OS_P_C    58 POWER_OS_Q_A    59 POWER_OS_Q_B
0                  0                  0                  0
60 POWER_OS_Q_C
0
  12. Wait for about 2 seconds to let the DSP data to be stabilized.
  13. On PuTTy, enter “PAR” commands to read the measurements and check that the obtained values are accurate.
  14. Repeat steps 8 through 13 to recalibrate the meter again if the accuracy does not meet the specification requirement.
  15. When accuracy meets the requirement, save the calibration constants into non-volatile memory by using the terminal command “DCS”.
Note: The command “DCD” allows the default calibration and configuration settings from the firmware (constant values stored in the application code) to be loaded. Otherwise, the system will always be booting up with the calibration values stored in non-volatile memory.