Thermo Scientific ThermoFlex Manual De Instrucciones página 198

The following values reflect the standard scaling and are the factory defaults:
Current (4ma – 20ma = the operating range of the chiller)
High ma
Low ma
High temp
Low temp
Current
With highlighted press enter to display:
USER MA
High MA
Low MA
High Temp
Low Temp
Calculating the default gain and offset for set point input for a high temp chiller:
The default settings for a high temp chiller will yield the following gain and offset for setpoint input:
Now 20ma will represent a setpoint of 90°
A separate gain and offset will also be calculated and are be applied to the DAC temperature output value.
The default settings for a high temp chiller will yield the following gain and offset for temperature output:
Now 90° = 20ma temperature output.
Note: Ensure that there is sufficient range in the voltage or current to provide enough resolution of temperature.
For example a voltage range of 0v – 1v to represent a temperature range of 0° - 150° would not have enough
resolution to provide stable readings.
Thermo Scientific
20.0ma
4.0ma
40.0° (standard temp chillers) 90.0° (high temp chillers)
5.0°
20.0
4.0
40.0
5.0
MilliAmpInputGain = (high temp – low temp) / (high ma – low ma)
MilliAmpInputOffset = high temp – (high ma * MilliAmpInputGain)
MilliAmpInputGain = (90.0 – 5.0) / (20.0 – 4.0) = 5.3125
MilliAmpInputOffset = 90 – (20 * 0.188235) = -16.25
(20.0 * 5.3125) + (-16.25) = 90.0°
MilliAmpOutputGain = (high ma – low ma) / (high temp – low temp)
MilliAmpOutputOffset = high ma – (high temp * MilliAmpOutputGain)
MilliAmpOutputGain = (20.0 – 4.0) / (90 – 5) = 0.188235294
MilliAmpOutputOffset = 20 – (90 * 0.188235) = 3.058823529
(90 * 0.188235294) + 3.058823529 = 20ma
Highlight the desired value and then press enter, the high-
light will flash. Use the up and down arrows to change the
value. Once the desired value is displayed press enter to
accept the change and stop the flashing.
Appendix D
ThermoFlex D-7