Specifications

while [13] Multi Setpoint Min attempts to keep all zones at

or above their respective setpoints.

Example

A 2-zone 2 setpoint application Zone 1 setpoint is 15 bar

and the feedback is 5.5 bar. Zone 2 setpoint is 4.4 bar and

the feedback is 4.6 bar. If [14] Multi Setpoint Max is

selected, Zone 1’s setpoint and feedback are sent to the

PID controller, since this has the smaller difference

(feedback is higher than setpoint, resulting in a negative

difference). If [13] Multi Setpoint Min is selected, Zone 2’s

setpoint and feedback is sent to the PID controller, since

this has the larger difference (feedback is lower than

setpoint, resulting in a positive difference).

2.8.8

Feedback Conversion

In some applications, it may be useful to convert the

feedback signal. One example of this is using a pressure

signal to provide flow feedback. Since the square root of

pressure is proportional to flow, the square root of the

pressure signal yields a value proportional to the flow. This

is shown in Illustration 2.28.

PID

130BA358.11

Ref.

signal

Desired

ow

P 20-07

FB conversion

Ref.

Flow

signal

Flow

P 20-04

P 20-01

Illustration 2.28 Feedback Conversion

Introduction to VLT® HVAC D... Design Guide

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