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The Time-Per-Unit error (TPU) for this setup is calculated as follows:
Pump rate (in seconds) = (0.1 L/min.) / (60 sec/min.) = 0.00166 L/sec.
Feed Delivery Rate = Cpdlv = 20.78 g/L * 0.00166 L/sec = 0.035 g/sec.
TPU = (1 / Cpdlv) * Vol
TPU = (1 / 0.035) * 3.5
TPU = 101
The TPU parameter has another important function in the 2730 software. PID regulation is enabled
whenever this parameter is not zero (See Section 6). No pump control output will occur if this
parameter is set to zero.
3. Error Direction
This parameter is set to either "under" or "over". Selecting "under" means that the user wishes to regulate
to the set point in an environment where the analyte is being consumed and as such tends to fall under the
set point. In this circumstance the control algorithm will attempt to regulate by making additions of
correction feed stock (which contains the analyte) to the controlled volume. Selecting the "over" error
direction assumes that the correction applied by the controller will have the effect of diluting or removing
analyte to perform regulation.
Example: In the case of a fermentation where glucose is the controlled analyte the user should select the
under error direction since the organisms in the fermentation will consume glucose, thereby forcing the
controller to add glucose via feed stock additions.
4. Analog Output
The voltage output of the analog interface is scaled relative to the calibration concentration. The user can
configure the analog output for each channel to represent 1, 2, 3, or 4 times the calibration concentration.
The output for each chemistry will track sample concentration as long as any chemistry other than "None"
has been selected from the measurement parameters menu. A channel that has been configured as "None"
will remain at 0 volts at the analog output. The analog outputs will change with the sample result for each
channel, black or white, regardless from which station the sample was obtained.
A discrete sample performed at a sample station different than
the monitor station will not affect the analog output.
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