998-2821
Rev. D
Page 13
4. Recommended Measurement Practices
4.1
Minimizing Variations in Signal
Turner Designs’ Little Dipper
2 has a flat surfaced optical window that might trap air
bubbles when positioned vertically. For this reason we recommend:
1) Installing Little Dipper
2 horizontally so that the mounting tee is in a vertical position.
2) That the flow direction is upward through the mounting tee.
This will ensure than any trapped air bubbles will be released and will not interfere with
sample measurement.
4.2 Temperature Considerations
Fluorescence is temperature dependent. The fluorescence signal from most fluorophores
will decrease as sample temperature increases. However, fluorescence values can be
corrected for temperature effects if the temperature correction coefficient of the fluorophore
being measured is known. Table 2 lists known temperature correction coefficients. These
coefficients can be used with recorded temperatures in the following equation to correct
temperature effects on fluorescence values:
Fr = Fs * e
[n (Ts-Tr)]
Where:
Fr = the calculated fluorescence at the reference temperature, Tr
Tr = the reference temperature
Ts = the sample temperature at time of reading Fs
Fs =
the sample’s fluorescence at the time the temperature of the sample is measured, Ts.
e = the base of natural log
n = Temperature Coefficient for whatever dye is used - see Table 2.
For greatest accuracy, determine the Temperature Coefficient of the dye or fluorophore
being used, record the sample temperature, and correct the sensor output for changes in
Direction of water flow
