16
Chapter 7 – Modbus Register Explained
Each 16 bit register holds a specific type of data. Sometimes more registers are required to
obtain the desired information.
0-1 : Actual Flow
The actual flow as displayed on the LCD of the meter (if available). The flow is in a Float
format, Byte order 1-0-3-2 (IEEE-754 encoded). We have pre-configured it to AI1, PV1, and
Channel 1.
2-3 : Totalizer Value
The totalizer value as displayed on the LCD of the 640S (if available). Use data type 32 bit
long integer. This has been pre-configured to AI2, PV2, and Channel 2.This returns the
cumulative total. This would provide a maximum number of 2
32
. However, the maximum
count in the 640S is only 10
8
. The decimal point, if used is stored in a separate register,
number 26.
4 : User Full Scale
This is a R/W word that contains the full scale of the instrument as set by the user. This only
affects the 4-20 mA. output, which would not be relevant for FF-BUS. Use data type 16 bit
short integer, Byte order 1,0. This register would work in one of the 40 Modbus registers.
5 : Factory Full Scale
This is a read only word that contains the full scale of the unit as set by the manufacturer. This
would be the full scale flow available to FF-BUS. Use data type 16 bit short integer, Byte
order 1,0. This register would work in one of the 40 Modbus registers.
6 : K-Factor
This is a calibration adjustment factor at the meter level. The K-Factor normally ships set to
1000 (1.000 the 3 decimals are always included). Use data type 16 bit short integer, Byte
order 1,0. This register would work in one of the 40 Modbus registers.
7 : Reset Total
Reading this address will return fixed data value of 1. Writing a 1 resets the total to zero in the
meter. Use data type 16 bit short integer, Byte order 1,0. This register would work in one of
the 40 Modbus registers, or could also be used in AO if needed.
8-9 : Calibration Date
The returned data contains the calibration date of the unit. Use data type unsigned 32 bit long
integer, Byte order 1-0,3-2. Example: ox 008D2CAB = dec 9252003 = 9/25/2013. You
could either use one of the AI analog inputs or treat it as two 16 bit unsigned integers in 2 of
the 40 Modbus registers.
10-12 : Flow Unit
Each 16 bit register contains two 8 bit ASCII characters of the flow unit. The returned word is
encoded in ASCII. You could read this value by using three of the 40 Modbus registers.
However, we recommend just using the FF-BUS PV_UNITS instead.