Modbus Communications 7828 Density Transmitter Technical Manual
D-4 78285000_AA
D.4 MODBUS REGISTER ASSIGNMENTS
Each register is identified by a unique number, and the list is organised by this number.
For each register, the contents are described, along with the data type of the contents.
The data type is always 32 bits unless stated otherwise. Variable names are given for
reference purposes only. They have no other use.
Note: All units locations (registers 3, 4, 5 and 26) MUST be set before entering other
values.
In some cases the data in a register is used to represent a non-numerical quantity, known
as an index. For example, the units of density can be kg/m
3
, gm/cc, lb/gal or lb/ft
3
and
these are represented by the numbers 91 to 94. Thus if Register 3 (line density) contains
the value (index) 91, this means that the units of line density are kg/m
3
. Index values
may, of course, be used for more than one register.
Tables of these indices are given in section D.5.
Register Function Data Type Index Table
(where applicable)
0 API product type Long integer D.5.1
1 API referral reference temperature 4-byte float
2 API referral reference pressure 4-byte float
3 Line density units Long integer D.5.2
4 Base density units Long integer D.5.2
5 Temperature units Long integer D.5.2
6 Special function calculation type Long integer D.5.3
7 Special function quadratic equation name Long integer D.5.4
8 Special function quadratic eqn. Units
1
Long integer D.5.5
9 Output averaging time Long integer D.5.6
10 Analog output selected variable Long integer D.5.7
14 PWM factor for 4mA on analog output Long integer
15 PWM factor for 20mA on analog output Long integer
20 PRT calibration factor 4-byte float
21 Crystal oscillator calibration factor 4-byte float
22 Diagnostics flags Long integer
23 Line density value when fixed by diagnostics 4-byte float
24 Base density value when fixed by diagnostics 4-byte float
25 Temperature value when fixed by diagnostics 4-byte float
26 Pressure Units D.5.2
27 Referral temperature for matrix referral Long integer D.5.8
29 Alarm coverage Long integer D.5.9
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