Honeywell VRX180 Program Control Loops, Control Loop Programming Structure, Loop Characteristics

Programming Function Blocks and Features

4.8 Program Control Loops

Control Loop Programming Structure

Programming a control loop requires configuring at least 3 function blocks: an Analog Input (AI), a loop algorithm and an Analog Output (AO). The term AO is applied to any type of control output; current (CAT), or time proportioning (DAT). The structure of the instrument permits many variations on this concept by allowing Calculated Values (CVs), both digital and analog, to be used as inputs to the different parameters within the control algorithms. It also allows a single parameter to be read by any number of function blocks in the unit.

Loop Characteristics

Table 4-8 lists loop characteristics to be aware of when configuring your instrument.

		Table 4-8 Loop Characteristics
Characteristic		What to be aware of
Choice of algorithm type	Two PID algorithm types, interactive and noninteractive. Noninteractive is the
		default type; however, this may be changed.
Gain or proportional band	PB is the default; however this may be changed.
7 loop types available	If the loop type is changed after a configuration is completed, all previously
		programmed entries will be deleted.
Diagnostic routines	You will be prompted to save your entries when leaving the loop program
		sequence. Diagnostic routines are executed at this time to verify all entries are
		complete and compatible. A FAIL message at this time may indicate incomplete
		entries or incompatible selections.
Split output tuning		When programming Split Output control loops, tuning parameter set #1 is
		automatically applied to output values between 0 and +100. Tuning parameter
		set #2 is automatically applied to output values between 0 and -100.
Programming loop		Control loop programming may require entry of numerical values, analog
parameters		parameters or discrete parameters as determined by the specific loop feature. In
		some cases the choices may be a numeral, an analog parameter or OFF. For
		parameter choices, refer to Table 3-2 for definitions of the discrete and analog
		parameter types available. OFF or NONE are listed as menu choices where
		applicable. Scroll to locate.
Minimum programming		Many of the prompted entry fields for control loops are optional. As a general
requirements		rule, the minimum entry information for control loops includes the Process
		Variable (PV) with range limits, set point value, some combination of gain, reset
		and rate, and a source for the feedback. In most cases, the feedback source will
		be the back-calculation output (BC) value of the analog output (AO) function
		block.

90 Video Recorder – User Manual