![Rosemount 3095FB Reference Manual Download Page 76](http://html.mh-extra.com/html/rosemount/3095fb/3095fb_reference-manual_1487388076.webp)
Model 3095FB Multivariable Transmitter with Modbus Protocol
Modbus Protocol Guide
Page 45 of 79
6.0 Calibration
6.1 Calibration
Each process variable in the 3095FB [differential pressure (DP), static pressure (SP), and pro-
cess temperature (PT)] can be trimmed. Two types of trims can be performed; offset (zero)
trim and slope (span) trim. To perform a trim the user only has to write the applied value to the
Modbus register while applying an accurate pressure or temperature to the 3095FB. For accu-
rate trimming the user should wait for the process variable to stabilize before attempting to
trim the transmitter. The 3095FB will do all the calculations needed to trim the transmitter.
The host should never write the offset (zero) and slope (span) trims at the same time.
For example, if the user wants to trim the DP from 0 to 100 inches of H
2
O@60 F there are
four steps.
1. Apply the offset(zero) DP to the transmitter. In this case apply 0 inches of H
2
O@60 F
and wait for the transmitter to stabilize.
2. Write the IEEE 754 floating point number to the register pair 437, 438. In this case
write a zero to the register pair.
3. Apply the slope(span) DP to the transmitter. In this case apply 100 inches of H
2
O@60
F and wait for the transmitter to stabilize.
4. Write the IEEE 754 floating point number to the register pair 439,440. In this case
write the number 100 to the register pair.
Table 6-1 Calibration
Modbus Access
DESCRIPTION
Address
Address
Type
Attributes
Functional
Area
Data / Control
0437,
0438
FP register
R/W, WP
DP calibra-
tion
DP offset (zero)
0439,
0440
FP register
R/W, WP
DP slope (span)
0443,
0444
FP register
R/W, WP
SP calibra-
tion
SP offset (zero)
0445,
0446
FP register
R/W, WP
SP slope (span)