Alpha Omega Instruments 800 Series User Manual

CONTROL METHODS
ON/OFF Control
1
Hysteresis
Cooling Action switches
on at Startup
Process Temperature
Cooling Action switches on when the
Process Temperature rises above the
Set Point plus the Hysteresis
Cooling Action switches off when the Process Temperature
drops below the Set Point
Set Point
This is the simplest form of control in that it is strictly full ON or full OFF. Therefore, the temperature will not always be
controlled to a steady state. (see diagram)
On/off control switches the output either full on or full off, depending on the input, set point and hysteresis values. The
hysteresis value indicates the amount the process value must deviate from the set point to turn on output. Increasing
the value decreases the number of times the output will cycle. Decreasing hysteresis improves controllability. With
hysteresis set to 0 the process value would stay closer to the set point, but the output would switch on and off more
frequently, causing “chattering.” Set Proportional Band 1 [Pb`1] (Main Menu) to 0 to set the controller to on/off
control mode.
ALPHA OMEGA INSTRUMENTS CORP. Instruction Manual
Series 800/850 Thermoelectric Cooler Controller Page 47
1
It is not recommended to use ON/OFF control when mechanical relays are installed in the Series 800/850 Thermoelectric Cooler
Controller. The factory recommends Solid State Relays if operation in the ON/OFF control method is necessary.
Set Point
Time
Heating Action switches off when the Process Temperature
rises above the Set Point
Heating Action switches
on at Startup
Hysteresis
Process Temperature
Heating Action switches on when the Process Temperature
drops below the Set Point minus the Hysteresis

Alpha Omega Instruments 800 Series Specifications

General

Brand	Alpha Omega Instruments
Model	800 Series
Category	Controller
Language	English