Installation manual
Series C Controller Configuration and Operation Manual
1-12 Athena Controls, Inc. 900M050U00
1.6.4 Second Setpoint
The 16C, 18C, and 25C controllers are available with an optional contact/digital input
switch. If a controller is equipped with the optional contact/digital input, then an external
device can trigger the use of a second setpoint. (See 14.8.2 for information about
selecting the function of the contact/digital input.) The operator cannot use the front
panel of the controller to switch to the second setpoint. However, once an external
device has switched the controller to use the second setpoint, the operator can change
the value of the second setpoint by means of the front panel. If the controller is on a
network, the value of the second setpoint can also be changed by a host computer. The
setpoint range for the second setpoint is configured using the setpoint low and high limit
parameters described in 5.6.2 and 5.7.2.
1.6.5 Remote Analog Setpoint
Use of a remote analog setpoint (RAS) is supported by only controllers that contain the
optional RAS card. If use of the remote analog setpoint is enabled (by the contact on the
RAS card being closed by an external signal), then the RAS value currently being
received by the controller is used as the active setpoint. The scaling of the RAS input is
configured using the remote analog setpoint low and high scale parameters as described
in 14.9.2
1.6.6 What Determines Which is the Active Setpoint
The active setpoint is the setpoint value currently being used for control. This is also the
setpoint currently being displayed. As described above, this setpoint can come from one
of several sources. The logic flow that determines which setpoint value is used is shown
below.
If a single setpoint ramp or multi-step ramp/soak recipe is active,
then the active setpoint equals the recipe setpoint.
Else if using the remote analog setpoint is enabled,
then the active setpoint equals the remote analog setpoint.
Else if using the second setpoint is enabled,
then the active setpoint equals the second setpoint.
Else active setpoint equals setpoint entered by means of the front panel (or
written to the controller by a host).