GE PQMII - Reading Long Integers from the Memory Map; Description; Example

CHAPTER 7: APPLICATIONS
PQMII POWER QUALITY METER – INSTRUCTION MANUAL 7–21
7.7 Reading Long Integers from the Memory Map
7.7.1 Description
The PQMII memory map contains data formatted as a long integer type, or 32 bits.
Because the Modbus protocol maximum register size is 16 bits, the PQMII stores long
integers in 2 consecutive register locations, 2 high order bytes, and 2 low order bytes. The
data can be retrieved by the following logic:
7.7.2 Example
Reading a positive 3 Phase Real Power actual value from the PQMII:
Following the method described above, we have:
DATA VALUE = (004F × 2
16
) + 35D1 hexadecimal
= 5177344 + 13777 converted to decimal
= 5191121 decimal
The most significant bit of the High Order register is not set, therefore the Data Value is as
calculated. Applying the Units and Scale parameters to the Data Value, we multiply the
Data Value by 0.01 kW. Therefore the resultant value of 3 Phase Real Power as read from
the memory map is 51911.21 kW.
Reading a negative 3 Phase Real Power actual value from the PQMII:
READ THE HIGH ORDER REGISTER AND
STORE THIS VALUE INTO “A”
READ THE LOW ORDER REGISTER AND
STORE THIS VALUE INTO “B”
IS THE MOST SIGNIFICANT BIT OF THE HIGH
ORDER REGISTER SET?
i.e. is HIGH ORDER REGISTER > 32767?
YES
DATA VALUE = (A x 2 ) + B
16
NO
(DATA VALUE = DATA VALUE – 2
32
)
OR
APPLY 2’s COMPLEMENT TO DATA VALUE;
THE SIGN IS IMPLIED TO BE NEGATIVE
DATA VALUE = DATA VALUE
Register Actual Value Description Units & Scale Format
02F0 004Fh 3 Phase Real Power (high) 0.01 × kW F4
02F1 35D1h 3 Phase Real Power (low) 0.01
× kW F4
Register Actual Value Description Units & Scale Format
02F0 FF3Ah 3 Phase Real Power (high) 0.01 × kW F4
02F1 EA7Bh 3 Phase Real Power (low) 0.01
× kW F4