Maxim Integrated 71M6541 Demo Board - Manual (Page 31)

71M6541 Demo Board REV 3.0 User’s Manual
31 Rev 4.0
Table 1-9: IMAX for Various Shunt Resistance Values and Remote Sensor Types
Remote
Sensor
Interface
Rated
Current
[A]
Max. Voltage
at IAP/IAN
[mV]
Shunt
Resistor
Value [µ
Ω]
IMAX
[A]
IMAX En-
try at MPU
0x03
WRATE for
kH = 1.0 and
VMAX = 600 V
CE ad-
dress
0x30
71M6601 60 62.5
500 88.39 +884 383 2483
400 110.49 +1105 497 2483
300 147.31 +1473 638 2483
250 176.78 +1768 766 2483
200 220.97 +2209 957 2483
160 276.21 +2762 1196 2483
120 368.28 +3683 1595 2483
71M6201 200 17.86
75 168.4 +1684 729 8691
50 252.6 +2526 1094 8691
25 505.1 +5051 2188 8691
The meter constant kh (Wh per pulse) is calculated as follows:
Kh = 109.1587* VMAX * IMAX / ( SUM_SAMPS * WRATE *X),
where
VMAX = RMS voltage at the meter input corresponding to 176.8 mV RMS at the VA pin of the
71M6541. This value is determines by the divider ratio of the voltage-divider resistors. For the
71M6541 Demo Board, this value is 600.
IMAX = RMS current through one current sensor corresponding to 176.8 mV RMS at the IAP/IAN or
IBP/IBN pins of the 71M6541, as determined by the formula above.
Note: For the IBP/IBN pins, no physical analog voltage exists due to the digital nature of the cur-
rent measurement via the remote interface.
SUM_SAMPS = The value in the SUM_SAMPS register in I/O RAM (2520 for this version of the Demo
Code).
WRATE = The value in the pulse rate adjustment register of the CE.
X = The pulse rate adjustment modifier, determined by the PULSE_FAST and PULSE_SLOW bits in
the CECONFIG register.
A kh of 1 (1.00 Wh per pulse) is achieved by the following combination of system settings:
VMAX = 600 V
IMAX = 368.3 A, based on R
S
= 120
μΩ
SUM_SAMPS = 2520
WRATE = 1595, based on X = 6, and PULSE_FAST = 0 and PULSE_SLOW = 0
1.10.5 DETERMINING THE TYPE OF 71M6X0X
Sometimes it is useful to be able to determine the type of 71M6X0X Remote Sensor Interface that is mounted
on the Demo Board. The CLI can be used to find out which 71M6X0X Remote Sensor Interface is present, us-
ing the following steps:
1) Type 6R1.14 at the command prompt (>).
2) The CLI will respond with a two-byte hex value, e.g., E9DB.
3) Write the hex value out as binary sequence, e.g., 1110 1001 1101 1011. Bits 4 and 5 determine the
type of the 71M6X0X Remote Sensor Interface, as shown in Table 1-10.