1.2.7.1.2 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, paying special attention to the configuration related to the hardware connected to the metrology inputs
  2. Open the METROLOGY_CONFIGURE_CALIBRATE_CALCULATE.xlsx spreadsheet, and go to the "Step-by-step guide" sheet, and follow the steps.
    Note: The steps described can change depending on the version of the Excel file.
  3. Configure the input sources and the meter tester if used (meter form, voltage, current, and so on). In this example, a PIC32CXMTSH board will be calibrated using a WECO tester, configured to generate 1A and 220V to each phase, at 50 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 1-47. Input Sources Configuration
  5. If voltage-to-voltage phase correction is desired, write “1” in the yellow cells. If enabled, the metrology library will correct the phase shift between the voltage vectors. Then select channels to calibrate, in this case, for PIC32CXMTSH channels A and B are selected.
    Figure 1-48. Voltage-to-Voltage Phase Correction and Channel Selection
  6. 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 1-49. Set Default Values as Groups
    >DCM( 34:20000000; 35:20000000; 36:20000000; 37:20000000; 38:20000000; 39:20000000; 40:20000000 )
Set 34 Is Ok !
Set 35 Is Ok !
Set 36 Is Ok !
Set 37 Is Ok !
Set 38 Is Ok !
Set 39 Is Ok !
Set 40 Is Ok !
>DCM( 41:0; 42:0; 43:0; 44:0; 45:0; 46:0; 47:0 )
Set 41 Is Ok !
Set 42 Is Ok !
Set 43 Is Ok !
Set 44 Is Ok !
Set 45 Is Ok !
Set 46 Is Ok !
Set 47 Is Ok !
>

    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 1-50. Set Default Values Individually
  7. 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.
  8. On Terminal, 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 1-51. Read the Measured Parameters from the Board (Commands PAR)
    Figure 1-52. Read DSP_CONTROL Registers (Command DCR)
    Figure 1-53. Read DSP_STATUS Register (Command DSR)
    Figure 1-54. Read DSP_ACC Register (Command DAR)
  9. The spreadsheet calculates the calibration constants (the 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 1-55. Set Calibration Constants as Groups
      >DCM(34:0FCF598F; 35:2114B35A; 36:0FD3B6B1; 37:21131224)
Set 34 Is Ok !
Set 35 Is Ok !
Set 36 Is Ok !
Set 37 Is Ok !
>DCM(41:FFF9AAD4; 42:0; 43:FFE72DEF; 44:28A7B0)
Set 41 Is Ok !
Set 42 Is Ok !
Set 43 Is Ok !
Set 44 Is Ok !
>
    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 1-56. Set Calibration Constants Individually
  10. Read the control registers (command DCR) to check that the calibration registers were successfully updated (values in bold):
    >DCR
00 STATE_CTRL      01 FEATURE_CTRL    02 HARMONIC_CTRL   03 METER_TYPE
2                  700                0                  CCC
04 M               05 N_MAX           06 PULSE0_CTRL     07 PULSE1_CTRL
0                  1130               810601D0           810201D0
08 PULSE2_CTRL     09 P_K_t           10 Q_K_t           11 I_K_t
110401D0           500000             500000             500000
12 S_K_t           13 CREEP_THR_P     14 CREEP_THR_Q     15 CREEP_THR_I
500000             2E9A               2E9A               212D
16 CREEP_THR_S     17 PWR_OFFS_CTRL   18 PWR_OFFS_P      19 PWR_OFFS_Q
2E9A               0                  0                  0
20 PWR_OFFS_S      21 SWELL_THR_VA    22 SWELL_THR_VB    23 SWELL_THR_VC
0                  5EAB918            5EAB918            5EAB918
24 SAG_THR_VA      25 SAG_THR_VB      26 SAG_THR_VC      27 K_IA
1A2EC26            1A2EC26            1A2EC26            4D291
28 K_VA            29 K_IB            30 K_VB            31 K_IC
19CC00             4D291              19CC00             4D291
32 K_VC            33 K_IN            34 CAL_M_IA        35 CAL_M_VA
19CC00             4D291              FCF598F            2114B35A
36 CAL_M_IB        37 CAL_M_VB        38 CAL_M_IC        39 CAL_M_VC
FD3B6B1            21131224           20000000           20000000
40 CAL_M_IN        41 CAL_PH_IA       42 CAL_PH_VA       43 CAL_PH_IB
20000000           FFF9AAD4           0                  FFE72DEF
44 CAL_PH_VB       45 CAL_PH_IC       46 CAL_PH_VC       47 CAL_PH_IN
28A7B0             0                  0                  0
48 CPTR_CTRL       49 CPTR_BUFF_SIZE  50 CPTR_ADDR       51 Reserved1
3F00               0                  0                  0
52 Reserved2       53 Reserved3       54 ATS_CTRL_20_23  55 ATS_CTRL_24_27
0                  0                  1010103            7010101
56 ATS_CTRL_28_2B  57 Reserved4       58 PWR_OFFS_P_A    59 PWR_OFFS_P_B
3                  0                  0                  0
60 PWR_OFFS_P_C    61 PWR_OFFS_Q_A    62 PWR_OFFS_Q_B    63 PWR_OFFS_Q_C
0                  0                  0                  0
>
  11. Wait for about 2 seconds to let the DSP data to be stabilized.
  12. On Terminal, enter PAR commands to read the measurements and check that the obtained values are accurate.
  13. Repeat steps 8 through 12 to recalibrate the meter again if the accuracy does not meet the specification requirement.
  14. When accuracy meets the requirement, save the calibration constants into non-volatile memory by using the terminal command DCS.
    Figure 1-57. Correct Results after Calibration
    >DCS
Save Data Is Ok !
>
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.