• For each sample, you must be able to obtain a laboratory concentration value at line
density and line temperature.
Procedure
1. Collect data for Comparison 1.
a. Take a concentration reading from the meter and record line density and line
temperature.
b. Subtract the meter value from a reference device.
c. Obtain a laboratory value for concentration at line density and line 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 line
temperature.
c. Subtract the meter value from a reference device.
d. Obtain a laboratory value for concentration at line density and line temperature,
in the units used by the meter.
3. Populate the following equation with values from each comparison.
Concentration
Lab
= × Concentration
Meter
+
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.
• Using the Field Communicator: Configure > Manual Setup > Measurements >
Conc Measure (CM) > Trim CM Process Variables
7. Take another concentration reading from the meter, and compare it to the
laboratory value.
• If the two values are acceptably close, the trim is complete.
• If the two values are not acceptably close, repeat this procedure.
Example: Calculating the trim slope and the trim offset
Comparison 1
Laboratory value 50.00%
Meter value 49.98%
Comparison 2 Laboratory value 16.00%
Meter value 15.99%
Measurement support
Configuration and Use Manual 139
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