GE PQMII Instruction Manual

Contents

CHAPTER 7: APPLICATIONSPQMII POWER QUALITY METER – INSTRUCTION MANUAL 7–217.7 Reading Long Integers from the Memory Map7.7.1 DescriptionThe 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 longintegers in 2 consecutive register locations, 2 high order bytes, and 2 low order bytes. Thedata can be retrieved by the following logic:7.7.2 ExampleReading 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 decimalThe most significant bit of the High Order register is not set, therefore the Data Value is ascalculated. Applying the Units and Scale parameters to the Data Value, we multiply theData Value by 0.01 kW. Therefore the resultant value of 3 Phase Real Power as read fromthe memory map is 51911.21 kW.Reading a negative 3 Phase Real Power actual value from the PQMII:READ THE HIGH ORDER REGISTER ANDSTORE THIS VALUE INTO “A”READ THE LOW ORDER REGISTER ANDSTORE THIS VALUE INTO “B”IS THE MOST SIGNIFICANT BIT OF THE HIGHORDER REGISTER SET?i.e. is HIGH ORDER REGISTER > 32767?YESDATA VALUE = (A x 2 ) + B16NO(DATA VALUE = DATA VALUE – 2 32)ORAPPLY 2’s COMPLEMENT TO DATA VALUE;THE SIGN IS IMPLIED TO BE NEGATIVEDATA VALUE = DATA VALUERegister Actual Value Description Units & Scale Format02F0 004Fh 3 Phase Real Power (high) 0.01 × kW F402F1 35D1h 3 Phase Real Power (low) 0.01 × kW F4Register Actual Value Description Units & Scale Format02F0 FF3Ah 3 Phase Real Power (high) 0.01 × kW F402F1 EA7Bh 3 Phase Real Power (low) 0.01 × kW F4