Despatch Protocol 3 Controller - Manual (Page 15)

Protocol 3 Controller Owner’s Manual T HEORY OF O PERATION
Version 1.2 15
Copyright © 2013 by Despatch Industries.
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3.
Theory of Operation
The Protocol 3 is a microprocessor based digital
temperature controller designed for simple and flexible
oven operation (Figure 1). The Protocol 3 controller
operates as a dual-functioning controller/high limit
instrument. The control portion utilizes a
time-proportioning voltage signal to control heating
devices with minimal temperature fluctuations.
The high limit portion protects the product and/or the
oven from overheating. If the product being processed has a critical high temperature limit, the
high limit setpoint should be set to a temperature somewhat below the temperature at which the
product could be damaged. If the product does not have a critical high temperature limit, the high
limit setpoint should be set 5 to 15 degrees higher than the maximum programmed setpoint at
which the oven will operate.
The Protocol 3 controller provides three primary operating modes:

Manual : Oven operates continuously at a fixed temperature until turned off.

Timer : Oven operates at a fixed temperature for a user-selected time period, and then
automatically turns off.

Profile : Temperatures increase or decrease as defined by 255 segments that can be allocated
to 64 ramp and soak profiles. The profiles can be linked to provide additional temperature
combinations.
The Protocol 3 controlled is equipped to allow a ramp/soak temperature control, which maintains
oven temperature with either a fixed setpoint or a ramp/soak profile.
3.1. System Control
—In General

The Protocol 3 controller provides outputs for the cooling fan, door lock switch/door release
pushbutton, and optional beacon light

A number of profiles for oven heating cycles are stored in the Protocol 3 controller. Access
profiles using the Protocol 3 keypad

The Protocol 3 controls the solenoid valves in an inert atmosphere oven for purge, maintain
and water cooling operation

The Protocol 3 can also be operated remotely with a PC running Protocol Manager software.
3.1.1. High-Limit Function
The Protocol 3 controller has an integrated high limit function which disables the heater output
when tripped. The High-Limit temperature is displayed as HLPV (Manual Mode only).
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 below the setpoint (or increase the high limit setpoint) and
then press . The indicator will turn off.
Figure 1. Operator Interface.