Meter value 64.93 %
Concentration offset: −0.72
13.3 Adjust concentration measurement with Trim Slope
and Trim Offset
Trim Slope and Trim Offset adjust the meter's concentration measurement to match a reference value.
Tip
You can adjust concentration measurement by applying the trim offset only, or by applying both the trim
offset and the trim slope. For most applications, the trim offset is sufficient.
Prerequisites
• Ensure that the active matrix is the one that you want to trim. You can set the offset and slope separately
for each matrix on your transmitter.
• For each sample, you must be able to obtain a laboratory concentration value at line density and sample
temperature.
Procedure
1. Collect data for Comparison 1.
a) Take a concentration reading from the meter and record line density and sample temperature.
b) Subtract the meter value from a reference device.
c) Obtain a laboratory value for concentration at line density and sample temperature, in the units
used by the meter.
2. Collect data for Comparison 2.
a) Change the concentration of your process fluid.
b) Take a concentration reading from the meter and record line density and sample temperature.
c) Subtract the meter value from a reference device.
d) Obtain a laboratory value for concentration at line density and sample temperature, in the units
used by the meter.
3. Populate the following equation with values from each comparison.
Concentration
Lab
= A × Concentration
Meter
+ B
4. Solve for A (slope).
5. Solve for B (offset), using the calculated slope and one set of values.
6. Enter the results as the trim slope and the trim offset.
• Using ProLink III: Choose Device Tools → Configuration → Process Measurement →
Concentration Measurement, set Matrix Being Configured to your matrix, and enter Trim Slope
and Trim Offset.
Configuration and Use Manual Measurement support
MMI-20020954 March 2021
Configuration and Use Manual 113
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