User guide

Protocol Plus Owner’s Manual THEORY OF OPERATION
Version 2 13
Copyright © 2010 by Despatch Industries.
All rights reserved. No part of the contents of this manual may be reproduced, copied or transmitted in any form or by any
means including graphic, electronic, or mechanical methods or photocopying, recording, or information storage and
retrieval systems without the written permission of Despatch Industries, unless for purchaser's personal use.
3.1. System Control—In General
• The Protocol Plus controller provides outputs for the cooling fan, door lock
switch/door release pushbutton, and optional beacon light
• As many as eight profiles for oven heating cycles are stored in the Protocol Plus
controller. Access profiles using the Protocol Plus keypad.
• The Protocol Plus controls the solenoid valves in an inert atmosphere oven for purge
and maintain operation
3.1.1. High-Limit Function
The Protocol Plus controller has an integrated high limit function which disables the
heater output when tripped. Find High-Limit temperature readouts on LCD Line #2 in all
Modes (Stop, Run, Hold, and Standby) except Setup Mode. High-Limit temperature is
displayed for 10 seconds, alternating with current Mode and Status display for 10
seconds. The control will not allow the high limit setpoint to be set below the current
setpoint value.
If the high limit trips, the Hi-Limit indicator will light and the relay must be manually
reset. Allow the oven to cool several degrees (or increase the high limit setpoint) and then
press Reset. The indicator will turn off.
3.1.2. Optional Serial Communications Hardware
Optional MODBUS RS422/485 serial communications hardware may be installed on the
Protocol Plus controller, with a 9-pin communications port located on rear of oven. This
provides the ability to network the oven(s) with a host PC.
3.2.
Display Functions
The Protocol Plus controller has two displays. A dedicated LED upper display shows the
oven temperature (Figure 2). A two line LCD lower display provides information on
control status, high limit temperature and allows changes to be made to the control
settings. Figure 3 shows a schematic of the Protocol Plus face plate.