Rainbow Electronics AT73C502 User Manual
Page 11
AT73C500
11
It is recommended that 50 Hz meters are operated from
3.2768 MHz crystal. In 60 Hz system, a 3.93216 MHz clock
is normally used. Because the clock frequency generates a
time reference for energy calculations, the content of
energy registers and also the pulse rate of impulse outputs
will change when crystal is changed. For example, the
nominal meter constant and display pulse rate of 60 Hz
meter (3.93216 MHz clock) is:
and
The LSB of energy registers correspond to 0.33Wh instead
of 0.4Wh, as follows:
The pulse rate can be scaled to 100 imp/kWh by program-
ming value 5 to MCC coefficient, as below:
which equals 100 impulses per kilowatt hour.
The following table summarizes the contents of all mea-
surement registers.
MC
60Hz
50Hz
--------------
1250
imp
kWh
------------
×
1500
imp
kWh
------------
=
=
DP
60Hz
50Hz
--------------
100
×
imp
kWh
------------
120
imp
kWh
------------
=
=
E
LSB
3.2768MHz
3.93216MHz
----------------------------------
0.4Wh
×
0.333333
…
Wh
=
=
IMP
(25
MCC)
1
imp
---------
E
LSB
×
+
30
1
imp
---------
0.3333
…
Wh
×
10
Wh
imp
---------
=
=
=
Register
Conditions
Full Scale Output (hex)
Resolution (hex)
REG0 - REG2
U = 270V, I = 80A, PF = 1
258F C2F7
34.276 µW
REG3 - REG5
U = 270V, I = 80A, PF = 0
2231 594D
37.653 µVAr
REG6 - REG8
U = 270V, I = 80A
258E
2.2467 VA
REG9 - REG11
PF = 1
PF = -1
7FFF
8001
0.0000305
-0.0000305
REG12 - REG15
W = 1.718GWh
FFFF FFFF
0.4Wh
REG16
∆
T = 238609.3h
FFFF FFFF
0.2s
REG17
50*T = 40.959s
7FFF
1.25 ms
REG19 - 21
U = 270V
7A8B
8.6 mV
REG22 - 24
I = 80A
7DA4
2.5 mA