Digital Temperature Controller Reference Manual

2.Technical Description
2.1 Introduction
TECHNICAL DESCRIPTION
The Digital Temperature Controller has three fundamental components to suit many
applications such as diffusion furnaces and broadband conveyor furnaces. The main
components are:
a) Controller Unit
b) Program Unit
c) Output Expander Units
The hardware and software for the Temperature Control Loop, the heart of the DTC, is
contained in the Controller Unit. The user interface is provided by the Program Unit and the
Output Expander Unit allows up to 15 temperature control zones to be used (in broadband
conveyor furnaces)
2.2 Controller unit
The controller unit is the main part of the DTC. This unit is responsible for collecting all the
data from the thermocouples and providing control of the zones in the furnace. All the
boards are connected via a specially designed bus on a motherboard. A technical description
of the boards is given in the following sections:
2.2.1 Pre-amplifier board
The 3-channel preamplifier board is used to lineairize and amplify the mV signal originating
from the thermocouples into a 0-10V signal that can be processed by the processor board.
Five (5) slots are available so a maximum of 15 control zones can be monitored. For a
diffusion furnace the slots 1(&2) are used for the spike thermocouple signals (1 for a 3-zone
furnace, 1&2 for a 5-zone furnace). Slots 5&4 are used for the paddle thermocouple signals
(5 for a 3-zone furnace, 5&4 for a 5-zone furnace).
2.2.2 Converter board
The converter board contains the 16-bit A-D converter, which converts the analog
(amplified) thermocouple signal into a digital signal that can be used by the processor board.
The full description of its operation is given in the description of the Hardware Temperature
Control Loop.
In the event that no DPC is present (which normally is used to select a temperature recipe)
the converter board is capable of selecting the desired temperature recipe. The converter
board contains 4 inputs for recipe selection, in case there is no connection between the DTC
and DPC. These inputs are connected to the terminals 13-16. These inputs have pull-up
resistors, so that an open input corresponds to a logical 1 input. The digital inputs are active
DIGITAL TEMPERATURE CONTROLLER REFERENCE MANUAL 2-1