5.2.4 Control

This selects the control algorithm, which may be PID heat and/or cool or an ON/OFF. The control algorithm may also be disabled in which case all outputs configured for control will revert to off in the case of a switching output or 0% power demand in the case of an analogue output.

 

P7

Select P7 to configure Control Type.

Having defined a control type it will be necessary to allocate control outputs using P11/P12/P13/P14.

 

Control options are described in section 7.1

 

 

 

 

None

Control action disabled

HP

PID heating

(factory default)

The control function block is configured for PID (three term) heating, no cooling. Typical applications include furnaces and ovens.

CP

PID cooling

The control function block is configured for PID (three term) cooling, no heating. May be used in cryogenic applications.

HP.CP

PID heat + PID cool

The control function block is configured for PID (three term) heating and PID cooling. Typical applications include extruder temperature control.

Ho.CP

ON/OFF heat + PID cool

The control function block is configured for ON/OFF heating and PID (three term) cooling.

 

Ho

ON/OFF heating

The control function block is configured for ON/OFF heating, no cooling. Simple heat only applications.

 

 

Co

ON/OFF cooling

The control function block is configured for ON/OFF cooling, no heating. Simple cool only applications

 

 

HP.CO

PID heat + ON/OFF cool

The control function block is configured for PID (three term) heating and ON/OFF cooling. Typical applications include extruder temperature control.

 

 

Ho.Co

ON/OFF heat + ON/OFF cool

The control function block is configured for ON/OFF heating and cooling. Simple heat/ cool applications.

 

 

 

 

P8

Select P8 to configure Non Linear Cooling Type.

P8 is only shown if the control type, P7, is heat and cool.

 

Different cooling mediums change the effectiveness of cooling in a non linear way. This parameter selects cooling characterisation to match the type of cooling medium. It is typically used in the control of extruder barrel temperatures where the cooling medium may be water, oil or forced air. When using non-linear cooling it is common practice to pulse the coolant using a relay, logic output. This is determined by the hardware fitted.

 

This is typically used for extruder applications and is described further in section 7.1.6 ‘Cooling Algorithm’.

Lin

Linear

(factory default)

The characterisation of the cool output is linear

oiL

Oil

Being non-evaporative, oil cooling is pulsed. It is deep and more direct and will not need such a high cool gain as fan cooling.

H2o

Water

A complication with water-cooling comes if the zone is running well above 100°C.

 

Usually the first few pulses of water will flash off into steam giving a greatly increased cooling capacity due to the latent heat of evaporation.

 

When the zone settles down, less or even no evaporation is a possibility and the cooling is less severe.

 

To handle evaporative cooling, water cool mode would generally be chosen.

This technique delivers much shortened pulses of water for the first few percent of the cooling range, when the water is likely to be flashing off into steam. This compensates for the transition out of the initial strong evaporative cooling.

 

 

FAn

Forced air (Fan)

This is much gentler than water cooling and not so immediate or decisive because of the long heat transfer path through the finned aluminium cooler and barrel.

 

With fan cooling, a cool gain setting of 3 upwards would be typical. Delivery of pulses to the blower is such that the on time increases with percentage cool demand determined by the controller.