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Standard Operations
Common examples for formulas are “LOAD” or “DELTA-pH” (Table 22):
•Load Basin1=concentration x flow
•Delta-pH=(pH IN) – (pH OUT)
Important Note: Formulas are not checked for validity.
5.15.2 Add a formula with measurement values from other probes
To add formulas, which use measurement values from other probes:
1. Add the measurement value to the letter assignment list.
a. Select the ADD option and confirm.
b. Select the device with the measurement.
c. Select the measurement from the selected device. A new letter is displayed within
the letter assignment list.
2. Use the letter in the formula as a variable.
Note: All capital letters (A-Z) can be used in a formula.
5.15.3 Formula operations
Formulas can contain arithmetic and logical operations, numeric functions and
parenthesis to control the evaluation order.
Arithmetic operations like addition, subtraction, division or multiplication are based on
numeric calculations. Each channel of the relay or analog output card (internal or
external) can run the formula option. Arithmetical calculation results are preferred to drive
analog output channels.
Logical operations like AND,OR,NOR, XOR are binary based calculations, the result is
either true or false (0 or 1). Logical operations typically drive a relay, because relays
prefer to stay either ON or OFF which fits to the logic operation results.
Table 22 Formula settings—Example
Function Description
Name LOAD
Location BASIN1
Unit kg/h
Parameter Q
Formula (AxB)/100
Add (Tag) A=Nitrate NO3 1125425 NITRATAX plus sc
B=Volume m3/h Q