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3.1 Command Menu
Scaling Factors
As indicated previously, the TIM-100/120 display and menu items do not show a decimal point.
Depending on the controller or menu parameter in question, a decimal point is implied in the
displayed value.
SENTRY
Controller
Scaling Factor Description
SENTRY 1510 Pressure set point (Pres Sp1), actual pressure read-back (Pres) and full
scale pressure (Pres FS) have an implied decimal point to the left of the
second digit (from the right). A scaling factor of 100 is used. The implied
units are in millimeters of water column.
Example: The displayed value 2540 equals 25.40 mm H
2
O.
SENTRY 1000 Pressure set point (Pres Sp1), actual pressure read-back (Pres) and full
scale pressure (Pres FS) have an implied decimal point to the left of the
third digit (from the right). A scaling factor of 1000 is used. The implied
units are in inches of water column.
Example: The displayed value 1150 equals 1.150” H
2
O.
SENTRY 9000 Flow set point (Flow Sp1), actual flow read-back (Flow) and full scale flow
(Flow FS) have an implied decimal point to the right of the first digit (from
the right). No scaling factor is used. The implied units are in cubic feet per
minute.
Example: The displayed value 12 equals 12 CFM.
Modes of Operation
The TIM-100/120 is factory configured to operate in Pressure Mode (SENTRY 1000 and
SENTRY 1510) or Flow Mode (SENTRY 9000) depending on the type of exhaust controller to
be operated.
PID Control Loop
The TIM-100/120 contains a PID closed loop algorithm for controlling the SENTRY controller
stepper motor during a set point change. All the controllers used in conjunction with the TIM-
100/120 have a patented PTI piston regulator. The piston regulator compensates for
fluctuations in facility exhaust to maintain a regulated process exhaust. The highly responsive
nature of the SENTRY controller off loads the PID algorithm such that the algorithm is only
required to change the controller set point. Once the new set point is reached, the piston in the
controller performs the corrective control.
Note:
•
In most applications, only the gain function of the PID loop is used. This is preset at the factory and
does not typically require adjustment.
