58
MODSCAN ,the communication read-out value is 1 at address 253 and 26000 at address 254, that is ,Val_t=1×65536+26000=91536,
then Val_s = Val_t*0.01 = 915.36W.
For example: To read positive active energy IMP, the data can be read at address 300-301 MODSCAN in Int16eger reading mode by
MODSCAN , the communication read-out
value is 0 at address 300 and 19000 at address 301, that is, Val_t=19000=19000, then Val_s =Val_t*1=19000Wh=19kWh.
7.3.4
Active power, reactive power, apparent power and energy (primary side; W/Var/VA/kWh)
The series of measured values are read with 03 command of the Modbus-RTU communication protocol. Each
item occupies a float (two words). The power resolution is 0.01, and the correspondence between the communication
value and the actual value is as follows: Val_s=Val_t*0.01; the energy resolution is 1, and the correspondence
between the communication value and the actual value is as follows: Val_s=Val_t*1; Val_t is calculated as follows:
The floating point variable data type value uses the sign bit to represent the sign of the data, and the exponent and mantissa represent
the size of the data. The data format used by the meter is the IEEE754 data format, which has 24-bit precision, and the high bit of
mantissa is always "1", so it is not saved and the distribution of bits is as follows:
1 sign bit, 8 exponent bits, 23 mantissas bits, the sign bit is the highest bit, and the mantissa is the lowest 23 bits.
Specific examples are as follows:
Read-out number (2word, arranged from highest to lowest ,4 bytes in total (0x474B, 0xAC00), 32bit):
Sign bit S , Index bit E , Mantissa M
Sign bit S=0
，
("1" is negative, "0" is positive)
Calculate the index E=10001110 and convert it into a decimal number 142;
Calculate the mantissa M=100 1011 1010 1100 0000 0000 into a decimal number 4959232.
Calculation formula: primary side power
=
( 127)
23
( 1) 2
1
2
S
E
M
The result of the above example is as follows:
