CXX-UM-01850-EN-01
SPECIAL INSTOUCTIONS
Calibrating the PT100
Repeat these steps as needed, up to 6 ANA per card
1 Make sure to connect a known resistance or RTD calibrator to the PT100 input (2, 3 or 4 wire)
2 Set the PT100 factor to 1 0
3 Exit
Programming
mode and observe the ohms (which now displays the bits)
4 Divide the actual resistance by the observed bits The result is now the factor for the PT100 The temperature calculation
from the resistance is automatic and uses a 2nd order polynomial e
5 Return to the PT100 factor menu and set the factor equal to the result from step 4
PT100 FACTOR – Input bits × PT100 factor = Ohms
Calculation of Ohms to Temperature
The flow computer calculates the temperature from the measured resistance in ohms using a standard polynomial equation
A separate set of constants is used for -200° C…0° C than for 0° C…200° C
Description of Unit Calculations
For each input there is a linearization curve which must be programmed for correct operation of the computer
OTEE:
N
Data for each curve may be entered in any order The computer sorts all data into numerical order when you return to
the main menu on completion of programming This may result in data moved to a different point if it was not
entered numerically
K-Factor Calculation
The inputs and linearization graphs are processed as indicated below
1 A Pt100 input is provided for measuring the fluid temperature
2 The flow computer converts this input to a 4…20mA signal
3 The flow computer processes that signal using the five point mA versus temperature to obtain the temperature
4 The flow computer uses the 30 point temperature versus viscosity curve to calculate the viscosity from the temperature
5 The flow computer uses the temperature measurement to calculate the Strouhal and Roshkoe numbers, using the
formulas from the chart below
6 The flow computer uses the Stouhal and Roshkoe numbers to compensate the K-factor
Strouhal Number
1 + ( 3x α δT )
Roshkoe Number
1 + ( 2 x α δT )
Where:
α
Temperature coefficient
δ T
Calibration Temperature – Actual Temperature
Special Instructions
Page 27
February 2018
