Honeywell UDC3200 manual Algorithm Set Up Group, Alg On-Off

3.6 Algorithm Set Up Group

Function	Selections or
Prompt	Range of Setting
Lower Display	Upper Display
CONT ALG
	ON-OFF

PID A

ATTENTION

PID A should not be used for Proportional only action; i.e., no integral (reset) action. Instead, use PD+MR with rate set to 0.

PID B

Parameter Definition

The CONTROL ALGORITHM lets you select the type of control that is best for your process.

ON/OFF is the simplest control type. The output can be either ON (100 %) or OFF (0 %). The Process Variable (PV) is compared with the setpoint (SP) to determine the sign of the error (ERROR = PV– SP). The ON/OFF algorithm operates on the sign of the error signal.

In Direct Acting Control, when the error signal is positive, the output is 100 %; and when the error signal is negative, the output is 0 %. If the control action is reverse, the opposite is true. An adjustable overlap (Hysteresis Band) is provided between the on and off states.

ATTENTION Other prompts affected: OUT HYST

DUPLEX ON/OFF is an extension of this algorithm when the output is configured for a Duplex control algorithm. It allows the operation of a second ON/OFF output. There is a deadband between the operating ranges of the two inputs and an adjustable overlap (hysteresis) of the on and off states of each output. Both Deadband and Hysteresis are separately adjustable. With no relay action the controller will read 50 %.

ATTENTION Other prompts affected: OUT HYST and

DEADBAND

PID A is normally used for three-mode control. This means that the output can be adjusted somewhere between 100 % and 0 %. It applies all three control actions—Proportional (P), Integral (I), and Derivative (D)—to the error signal.

Proportional (Gain)—Regulates the controller’s output in proportion to the error signal (the difference between Process Variable and Setpoint).

Integral (Reset)—Regulates the controller’s output to the size of the error and the time the error has existed. (The amount of corrective action depends on the value of proportional Gain.)

Derivative (Rate)—Regulates the controller’s output in proportion to the rate of change of the error. (The amount of corrective action depends on the value of proportional Gain.)

PID B—Unlike the PID A equation, the controller gives only an integral response to a setpoint change, with no effect on the output due to the gain or rate action, and it gives full response to PV changes. Otherwise controller action is as described for the PID A equation. See note on PID A.

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