71M6521 Demo Board User’s Manual
Page: 32 of 111
© 2005-2009 TERIDIAN Semiconductor Corporation
Revision 2.18
In order to operate the
D6521T4A7
Demo Board with a current shunt sensor, the following measures must be taken:
a. Remove the jumper on JP17.
b. Make sure that L9 and L12 are removed and that R88 is installed
c.
Make sure that R24 is a 10k
Ω
resistor if IA_IN is the input channel for the current shunt, and that R106
is a 10k
Ω
resistor if IB_IN is the input channel for the current shunt.
d. The LIVE line must be connected to the spade terminal J4 (bottom of the board).
e. The blue and white pair of wires from the shunt resistor must be connected to contacts 1 and 2 on J3 if
IA_IN is the input channel or contacts 1 and 2 on J16 if IB_IN is the input channel.
The white wire must
be connected to pin 1, the blue wire must be connected to pin 2
.
f.
No connection is necessary for the green wire from the pre-wired shunt resistor.
1.8.6 ADAPTING DEMO CODE PARAMETERS TO OPERATION WITH SHUNT
RESISTOR
The
IMAX
variable has to checked for current shunt mode using the formula:
IMAX
= 177mV/R
shunt
The new value for IMAX (XRAM address 0x0A) should be entered, using the command line interface, as
follows (using the shunt resistor provided by TERIDIAN, R
shunt
= 400µ
Ω
, with resulting
IMAX
= 440A):
>)A=+4400
IMAX
values have a LSB resolution of 0.1A,
VMAX
values have a LSB resolution of 0.1V.
Since
IMAX
has been changed,
WRATE
has to be recalculated to maintain the Kh of 3.2Wh per
pulse, as shown in chapter 1.8.2.
WRATE
can be entered as follows:
>]11=+258
If desired, the CE of the Demo Code can be set to run with increased gain (8 instead of 1) of the current
channels, as sometimes required in current shunt mode due to low currents and low shunt resistances. This
can be done via the command line interface by the commands
>]10=5004
setting IA_8 to 8 by controlling IA_SHUNT (bit 2 of CESTATE at CE address
0x10), if IA_IN is connected to the shunt, or
>]2B=5008
setting IB_8 to 8 by controlling IB_SHUNT (bit 3 of CESTATE at CE address
0x10 if IB_IN is connected to the shunt.
The Demo Code will compensate for the increased gain, i.e. the energy and current readings do not have to
be scaled.
1.9 CALIBRATION PARAMETERS
1.9.1 GENERAL CALIBRATION PROCEDURE
Any calibration method can be used with the 71M6521 chips. This Demo Board User’s Manual presents
calibration methods with three or five measurements as recommended methods, because they work with
most manual calibration systems based on counting "pulses" (emitted by LEDs on the meter).
Naturally, a meter in mass production will be equipped with special calibration code offering capabilities
beyond those of the Demo Code. It is basically possible to calibrate using voltage and current readings, with
or without pulses involved. For this purpose, the MPU Demo Code can be modified to display averaged
voltage and current values (as opposed to momentary values). Also, automated calibration equipment can
communicate with the Demo Boards via the serial interface and extract voltage and current readings. This is
possible even with the unmodified Demo Code.
A complete calibration procedure is given in section 2.1.3 of this manual.
Regardless of the calibration procedure used, parameters (calibration constants) will result that will have to
be applied to the 71M6521 chip in order to make the chip apply the modified gains and phase shifts
necessary for accurate operation. Table 1-11 shows the names of the calibration constants, their function,
and their location in the CE RAM.
