F Calculate measurement errors using
reference chamber pressure
For evaluation purposes, you can use this procedure to determine the expected accuracy using the reference
chamber pressure. However, for most common applications, the accuracy will perform within 0.1% of
reading.
Your selection of control reference chamber pressure determines the range of possible measurement errors.
You can calculate the measurement error associated with different control reference chamber pressures and
use this procedure to determine the control reference chamber pressure.
Use this procedure to calculate the measurement error associated with several different reference chamber
pressures.
Procedure
1. Print out the appropriate calculation aid in
2. Record your process gas and the expected specific gravity range.
3. Record the Density Temperature Coefficient (DTC) for the meter.
The DTC is provided on the meter's calibration sheet and on a label inside the transmitter front cover.
4. Check the example references chamber pressures on the calculation aid and change them as needed.
5. Using the following equations, calculate the density range for each reference chamber pressure.
Figure F-1: Density range (minimum and maximum)
SG
min
= P x ρ
Air
x SG
min
SG
max
= P x ρ
Air
x SG
max
P
Reference chamber pressure (bara)
ρ
Air
Density of clean dry air (1.2 kg/m
-3
approximately)
SG
min
Specific gravity minimum value
SG
max
Specific gravity maximum value
6. Using the following equations, calculate the measurement error for each density range.
Figure F-2: Temperature coefficient error
Error
DTC
= DTC
ρ
max
x 100% / °C
DTC
Temperature coefficient for this meter
ρ
max
Maximum density value (kg/m
-3
)
Configuration and Use Manual
Calculate measurement errors using reference chamber pressure
MMI-20020954
March 2021
Configuration and Use Manual
187
