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When in the monitoring mode and when the 2700 is stabilized in terms of calibration drift, you will likely
want to change some of these parameters to minimize interference of calibration with monitor sampling.
For example, you may elect to disable autocalibrations related to time and number of samples, then use the
PreCal option under Monitor Setup. Alternatively, you may elect to disable time and calibrate after some
number of samples, or after some fixed time has elapsed. There is no "best configuration". It really
depends on your particular application.
Generally, you will not want to change temperature drift, cal shift or sample error parameters, since these
can be indicators of system problems. However, the flexibility to disable is there and may be exercised. If
you are writing a software program to remotely command the 2700/2730 system (via the RS232 port), you
may want to disable all autocalibration parameters and bring calibration frequency totally under your
software program control.
5.2.6
Analog /Control
The control signals for the white and black channel pumps are configured from the "SETUP" menu via the
"RunMode" option. Once in the RunMode, sub menu option 5, " Aux" (Auxiliary), will expose two
choices, Black channel setup or White channel setup. The two channel setups are identical but specific to
the channel involved (see the following). These parameters allow you to control pumps that will feed
additional nutrients or diluent to a reactor in order to achieve a desired set point.
Black or White Channel Setup
The channel control setup menus prompt users for four pieces of information, the analyte set point, Time-
Per-Unit error (TPU), the method of control (error direction) and the full scale concentration of each
analog output. The first three parameters pertain to control while the forth pertains to the analog output for
that channel. The following describes the setup considerations for each item.
1. Set Point
This parameter is the concentration at which the analyte will be regulated. It is assumed to be entered in
the units ascribed to the analyte (e.g. g/L, mg/L, etc.).
2. Time-Per-Unit error (TPU)
This is a factor that is computed by the user and entered into the instrument to allow it to perform
proportional control of the analyte in a quasi-static volume such as a fermentor or bioreactor. It reflects the
amount of time that the correction pump must be engaged to correct for an error in concentration equal to
the unit of measure (e.g. g/L, mg/L, etc.). In the case where analyte is added when the concentration falls
below the set point the optimal feed stock concentration and the TPU factor are calculated according to the
following formulae;
Caution: Setting or changing this parameter while controlling
will reset the integral portion of the PID algorithm and will
therefore affect regulation. See Section 6.
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