CS5480
6) If the phase offset is negative, then the delay should
be added only to the current channel. Otherwise,
add more delay to the voltage channel than to the
current channel to compensate for a positive phase
offset.
7.3.1 Temperature Offset and Gain Calibration
To obtain the optimal temperature offset (T
) register
OFF
value and temperature (T
) register value, it is
GAIN
necessary to measure the temperature (T) register at a
minimum of two points (T1 and T2) across the meter
operating temperature range. The two temperature
points must be far enough apart to yield reasonable
accuracy, for example 25°C and 85°C. Obtain a linear
fit of these points (y = m x + b ), where the slope (m)
and intercept (b) can be obtained.
Once the phase offset is known, the CPCCx and FPCCx
bits for that channel are calculated and programmed in
the PC register.
CPCCx bits are used if either:
•
The phase offset is more than 1 output word rate
(OWR) sample.
•
More delay is needed on the voltage channel.
T2
The compensation resolution is 0.008789° at 50Hz and
0.010547° at 60Hz at an OWR of 4000Hz.
Y = m • x + b
7.3 Temperature Sensor Calibration
Temperature sensor calibration involves the adjustment
m
of two parameters: temperature gain (T
) and
GAIN
temperature offset (T
must be set to 1.0 (0x 01 0000), and T
to 0.0 (0x 00 0000).
). Before calibration, T
OFF
GAIN
T1
b
must be set
OFF
T Register Value
Figure 26. T Register vs. Force Temp
T
and T
are calculated using the following
GAIN
OFF
equations:
b
m
----
T
=
OFF
T
= m
GAIN
DS980F2
65
APEX [ CIRRUS LOGIC ]
