Maxim Integrated 71M6541 Demo Board - Manual (Page 51)

71M6541 Demo Board REV 3.0 User’s Manual
51 Rev 4.0
For the control of GAIN_ADJB , we will need the following coefficients:
C
S2
: Since we assume that the shunt resistors are very similar with respect to their TC, we use the val-
ue found for the shunt connected at phase B ( PPMC
S
= -3331). Again, PPMC2
S
for the shunt resistor
is 0. Since this coefficient applies to the current measurement only, we will have to apply the ½ factor
mentioned above.
C
4X
: PPMC
4X
= -820 and PPMC2
4X
= -680, as already stated above. Since these coefficients apply to
the voltage measurement only, we will have to apply the ½ factor mentioned above.
C
6X
: PPMC
6X
= -960 and PPMC2
6X
= -610. Since these coefficients apply to the current measurement
only, we will have to apply the factor of ½ that was mentioned above.
C
VD
: The PPMC
VD
value of 788 determined for the voltage-divider.
We obtain the coefficients for GAIN_ADJB as follows:
• PPMC
B
= PPMC
S
/2 + PPMC
4X
/2 + PPMC
6X
/2 + PPMC
VD
/2 = -3331/2 - 820/2 - 960/2 + 788/2 = -2162
•
PPMC2
B
= PPMC22
S
/2 + PPMC2
4X
/2 + PPMC
6X
/2 = 0 - 680/2 -610/2 = -985
2.5 TESTING THE DEMO BOARD
This section will explain how the 71M6541F IC and the peripherals can be tested. Hints given in this section will
help evaluating the features of the Demo Board and understanding the IC and its peripherals.
Demo Board. It interfaces to a PC through a 9 pin serial port connector.
It is recommended to set up the demo board with no live AC voltage connected, and to
connect live AC voltages only after the user is familiar with the demo system.
BEFORE CONNECTING THE DEMO BOARD TO A CALIBRATION SYSTEM OR OTHER
HIGH-VOLTAGE SOURCE IT IS RECOMMENDED TO MEASURE THE RESISTANCE BE-
TWEEN THE LINE AND THE NEUTRAL TERMINALS OF THE DEMO BOARD WITH A MULTI-
METER. ANY RESISTANCE BELOW THE 1 M
Ω RANGE INDICATES A AFAULTY CONNEC-
TION RESULTING INDESTRUCTION OF THE 71M6541.
2.5.1 FUNCTIONAL METER TEST
This is the test that every Demo Board has to pass before being integrated into a Demo Kit. Before going into
the functional meter test, the Demo Board has already passed a series of bench-top tests, but the functional
meter test is the first test that applies realistic high voltages (and current signals from current transformers) to
the Demo Board.
Figure 2-12 shows a meter connected to a typical calibration system. The calibrator supplies calibrated voltage
and current signals to the meter. It should be noted that the current flows through the shunts or CTs that are not
part of the Demo Board. The Demo Board rather receives the voltage output signals from the current sensor. An
optical pickup senses the pulses emitted by the meter and reports them to the calibrator. Some calibration sys-
tems have electrical pickups. The calibrator measures the time between the pulses and compares it to the ex-
pected time, based on the meter Kh and the applied power.