Monitoring and Operating the Controller
202 UDC3500 Universal Digital Controller Product Manual 3/07
4.7.2 What happens when you change modes
Table 4-6 Changing Control Modes
Control Mode Definition
Manual to
Automatic Local
Setpoint
The Local Setpoint is usually the value previously stored as the Local Setpoint.
PV tracking is a configurable feature that modifies this. For this configuration,
when the controller is in manual mode, the local setpoint value tracks the process
variable value continuously. Thus, when the instrument is switched into Automatic
Mode, the local setpoint is set at the current PV value.
Manual or Auto
Local to Automatic
Remote SP
The Remote Setpoint uses the stored ratio and bias to calculate the control
setpoint.
Auto bias is a configurable feature, which modifies this. When it is selected the
transfer from automatic local to automatic remote or from manual remote to
automatic remote adjusts the bias based on the local setpoint such that
Bias = LSP – (RSP Input x R).
Automatic Remote
Setpoint to Manual
or Auto Local
Setpoint
If configured for local setpoint tracking, RSP, when the controller transfers out of
remote setpoint the last value of the remote setpoint is inserted into the local
setpoint.
If LSP tracking is not configured, the local setpoint will not be altered when the
transfer is made.
4.8 Setpoints
Introduction
You can configure the following setpoints for the UDC3500 controller.
• One to four Local Setpoints
• One to four Local Setpoints plus one Remote Setpoint
Refer to Subsection 3.20 – Control Set Up Group for configuration details.
W
henever the active Setpoint is shown in the Lower Display, an n appears to the left of
the Setpoint display.
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