90E32 Datasheet, PDF (28/71 Pages) Integrated Device Technology – Poly-Phase High-Performance Wide-Span Energy Metering IC

90E32
POLY-PHASE HIGH-PERFORMANCE WIDE-SPAN ENERGY METERING IC
5
CALIBRATION METHOD
5.1 NORMAL MODE OPERATION CALIBRATION
Calibration is done per phase and there is no need to calibrate for the
all-phase-sum (total) parameters. The calibration method is as follows:
Step-1: Register configuration for calibration
- Start to configure the System configuration Registers by writing
5678H to the ConfigStart register.
- The 90E32 automatically reset the configuration registers to their
default value.
- Program all the system configuration registers.
- Calculate and write the checksum to the CS0 register.
- Write 8765H to the ConfigStart register (enable checksum check-
ing).
- System may check the WarnOut pin to see if there is a checksum
error.
The start register and checksum handling scheme is the same
throughout the calibration process, so the following section does not
describe the start and checksum operation.
Step-2: Measurement calibration (per-phase)
- First calibrate offset at I = 0, U = 0 for current or/and voltage;
• Configure calculated channel Gain (The user needs to program
the PGA gain and DPGA gain properly in order to get the calcu-
lated gain within 0 to 2 in step-1).
• Read Irms/ Urms value.
• Calculate the compensation value.
• Write the calculated value to the offset register.
- Then calibrate gain at I = In (Ib), U = Un for current and voltage;
• Read Irms/ Urms value.
• Calculate the compensation value.
• Write the calculated value to the Gain register.
Step-3: Metering calibration (per phase)
- First calibrate the Power/ Energy offset.
• U = Un, I = 0.
• Read full 32 bits (or lower 16 bits) Active and Reactive Power
• Calculate the compensation values
• Write the calculated values to the offset registers respectively.
- Then calibrate Energy gain at unity power factor:
• PF=1.0, U = Un, I = In (Ib).
• Connect CF1 to the calibration bench;
• User/ PC calculate the energy gain according to the data got
from calibration bench
• Write the calculated value to the Energy Gain register.
- Then calibrate the phase angle compensation at 0.5 inductive
power factor.
• PF=0.5L, U = Un, I = In (Ib), Rated frequency = 50Hz, or 60Hz
according to the application;
• CF1 connected to the calibration bench;
• User/ PC calculate the phase angle according to the data got
from calibration bench;
• Write the calculated value to the Phase angle register.
5.2 PARTIAL MEASUREMENT MODE CALIBRA-
TION
The calibration method is as follows:
Step-1: Set the input current to zero and measure the current mean
value (set MeasureType = 1, write 1 to the ReMeasure bit (b14, PMCon-
fig) to trigger the measurement. Refer to the PMIrmsA register). Negate
the result register (the PMIrmsA/PMIrmsB/PMIrmsC registers) reading
(16-bit) and then write the result to the offset register.
Step-2: The output of Partial Measurement result =
ADC_input_voltage *PGA_gain*DPGA_gain*65536 / 1.2. For instance,
a 150 mVrms signal (from CT) with PGA = 1 gets 8192 in the RMS result
register.
Step-3: The user needs to do its own conversion to get meaningful
result. The scaling factor in user's software could be calibrated device
per device.
Calibration Method
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December 9, 2011