Digital Temperature Controller Reference Manual

Digital Temperature Controller 

Reference Manual 

Tempress ® Systems, Inc. 

DTC manual 

M420_01 January 2004

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Table of Contents 

TABLE OF CONTENTS 

1. Introduction .......................................................................1-1 

1.1 Scope of the manual.................................................................. 1-1 

1.2 Overview.................................................................................... 1-1 

1.3 DTC System Features ............................................................... 1-1 

1.4 Technical Specifications ............................................................ 1-4 

2. Technical Description.......................................................2-1 

2.1 Introduction................................................................................ 2-1 

2.2 Controller unit ............................................................................ 2-1 

2.2.1 Pre-amplifier board ....................................................... 2-1 

2.2.2 Converter board ............................................................ 2-1 

2.2.3 Microprocessor Board................................................... 2-2 

2.2.4 Communication board................................................... 2-3 

2.2.5 Output board ................................................................. 2-3 

2.2.6 Power Supply board...................................................... 2-4 

2.3 Hardware Temperature Control Loop ........................................ 2-4 

2.3.1 Input circuit.................................................................... 2-4 

2.3.2 Output circuit................................................................. 2-4 

2.4 Software Temperature Control Loop.......................................... 2-4 

2.4.1 Spike Control ................................................................ 2-5 

2.4.2 Paddle control ............................................................... 2-7 

3. DTC Configuration ............................................................3-1 

3.1 Introduction................................................................................ 3-1 

3.2 Diffusion furnaces ...................................................................... 3-1 

3.2.1 Furnace with DPC......................................................... 3-1 

3.2.2 Stand-alone................................................................... 3-1 

3.2.3 Furnace with source furnace, stand-alone .................... 3-1 

3.3 Conveyer furnaces..................................................................... 3-3 

3.3.1 Small band conveyors................................................... 3-3 

3.3.2 Broadband conveyors ................................................... 3-3 

DIGITAL TEMPERATURE CONTROLLER REFERENCE MANUAL I

TABLE OF CONTENTS 

3.3.3 Recipes......................................................................... 3-4 

3.4 Independent or Master/Slave Control ........................................ 3-4 

4. Installation and Calibration ..............................................4-1 

4.1 Installation ................................................................................. 4-1 

4.2 Calibration ................................................................................. 4-1 

4.2.1 Equipment required....................................................... 4-1 

4.2.2 Analog-to-digital converter board .................................. 4-2 

4.2.3 Channel input board with cold junction board ............... 4-3 

4.3 Repair ........................................................................................ 4-7 

DIGITAL TEMPERATURE CONTROLLER REFERENCE MANUAL II

List of figures 

LIST OF FIGURES 

Figure 1-1 DTC basic overview ............................................................... 1-1 

Figure 2-1 Jumpers position at processor board ..................................... 2-3 

Figure 2-2 Ramping comparisons ........................................................... 2-5 

Figure 2-3 Software temperature control loop ......................................... 2-6 

Figure 3-1 DTC Configurations ............................................................... 3-2 

Figure 3-2 Independent and Master/Slave control .................................. 3-4 

Figure 4-1 Converter Card and Rear Connector ..................................... 4-2 

Figure 4-2 Channel Input Card................................................................ 4-4 

DIGITAL TEMPERATURE CONTROLLER REFERENCE MANUAL III

1.Introduction 

1.1 Scope of the manual 

INTRODUCTION 

The Digital Temperature Controller (DTC) forms the heart of the system control together 

with the Digital Process Controller (DPC). This manual contains a technical description of 

the DTC for version 2I or higher and is mainly aimed at maintenance and service engineers. 

It includes technical information and calibration procedures of the DPC. This manual forms 

part of a series of manuals covering the full range of Amtech Tempress Systems products. 

The contents of this manual and drawings are to provide the necessary instructions and 

information for installing, adjustment, operating, maintenance, and understanding of the 

Amtech/Tempress Systems Digital Process Controller. 

1.2 Overview 

The Digital Temperature Controller (DTC) is designed for high accuracy control of 

temperature for diffusion and conveyor furnaces. Its modular design makes it suitable for the 

simplest application and easily expandable for the most complex applications. 

The DTC consists of two basic units: 

1. The temperature controller Unit 

2. Touchscreen Display and/or TSC-II 

For Conveyor Furnaces, Output Expander Units are provided to house the necessary extra 

output boards. 

1.3 DTC System Features 

Figure 1-1 DTC basic overview 

INDEPENDENT TEMPERATURE 

ZONES 

MASTER/SLAVE CONTROL 

A maximum of 15 temperature zones can be 

independently controlled. 

It is possible to operate six zones independently or 

in a master/slave configuration where one zone is 

the master of 4 or 5 other zones. 

DIGITAL TEMPERATURE CONTROLLER REFERENCE MANUAL 1-1

HIGH ACCURACY 

THERMOCOUPLE CONTROL 

FAST COOLDOWN 

SOFTWARE TEMPERATURE 

CONTROL LOOP 

TEMPERATURE RAMPING 

AUTOMATIC PROFILING 

RECIPE STORAGE 

TEMPERATURE ALARM 

INTRODUCTION 

The DTC's Analog to Digital converter gives 

temperature resolution to 0.05. 

The DTC provides temperature control using spike 

thermocouples at the outside of the process tube or 

paddle thermocouples inside the tube. 

This optional feature provides shorter cooling time 

for a higher production capacity. 

The temperature control uses a cascading PID loop 

of the spike or paddle thermocouple input signals. 

Gain control is provided for limiting the maximum 

power output. 

Temperature ramping is provided on all zones. This 

guarantees a long flat zone during and ramping up 

or down, by making use of calculated values from a 

profile table or continuously controlling the 

temperature using the paddle thermocouples 

Automatic profiling is continuously possible during 

the process or by means of specially programmed 

recipes. 

DTC and DPC versions 2I and higher provide an 

unlimited number of temperature setpoints in a 

process recipe. 

An alarm is generated when the temperature rise 

above or fall below programmable limits. The alarm 

limits can be in the range 0.1-25.5 oC. 

BROKEN THERMOCOUPLE ALARM An alarm is generated when a thermocouple is 

broken. In spike control the affected zone is 

maintained at approximate temperature by using the 

thermocouple break output table measured during 

profiling. If the zone is in paddle control and the 

thermocouples fails control is switched to the spike 

thermocouple. 


POWER FAIL ALARM 

CALIBRATION TEMPERATURE 

STORAGE 

5 TYPES OF THERMOCOUPLES 

THERMOCOUPLES INPUTS 

SIDE ZONES 

MODULAR SYSTEM 

ANALOG INPUT (0-5V) 

DIGITAL INPUTS 

BATTERY BACK-UP 

INTRODUCTION 

An alarm is generated when the heating element 

fails, power is interrupted or the SCR driving unit 

fails. 

Up to 16 calibration temperatures can be stored. 

The DTC supports several types of thermocouples. 

These are ptRh 13%, ptRh 10%, Platinel II, Nich-Ni 

(Type k) and ptRh 6%. 

The controller can contain up to 5 3-channel input 

boards. Each board inputs data from 3 

thermocouples, which may be any of the above 

types. 

Each zone can be coupled with 2 side zones (used in 

broadband Conveyor Furnaces). The gain of these 

zones is independently programmable. 

The modular construction of the DTC makes it 

easily expandable. This also improves the 

serviceability of the units. All boards are accessible 

from the front of the controller. 

This enables an external analog ramp unit to be 

connected. This is only applicable to zones 1, 2 and 

3 in a three-zone furnace tube. The 0 to 5V range 

correspond to 0 to 1000 oC below controller 

setpoint. Used for calibration of the converter board. 

These enable the selection of recipes by means of an 

external timing unit. (Only if there is no DPC) 

An external Ni-Mh battery maintains data stored in 

volatile memory for a minimum of 60 days after 

power is disconnected 


1.4 Technical Specifications 

MAX. NUMBER OF CONTROL 

ZONES: 

15 

SETPOINT RANGES: Type R, PtRh 13 % 0 - 1400.0 oC 

SETPOINT RESOLUTION: 

Type S, PtRh 10% 0 - 1400.0 oC 

Platinel II 0 - 1200.0 oC 

Type K, Nichr-Ni 0 - 1200.0 oC 

Type B, PtRh 6% 0 - 1400.0 oC 

0.1 oC 

DISPLAY RANGE: PtRh 6%, 10% and 13% 0 - 1499.9 oC 

PROPORTIONAL BAND 

RANGE: 

INTEGRAL RANGE: 

DERIVATIVE RANGE: 

% POWER: 

PROGRAMMABLE SLOPE 

RANGE: 

ALARM RANGE HL AND LL: 

Type K, Platinel II 0 - 1299.9 oC 

1 - 100 oC 

0 - 25.5 min. 

0-255 s. 

0-98% 

0-100.00 oC/min. 

STANDARD CONDITIONS: 30 days 1 µV. 

TEMPERATURE DRIFT: 0.2 µV/ oC max. 

SUPPLY VOLTAGE 

REJECTION: 

OUTPUT SAMPLE RATE: 

0.0-25.5 oC (deviation from setpoint) 

0.5 µV max. over supply range ( 10%) 

1 second 

INTRODUCTION 


OPERATING VOLTAGE: 

AMBIENT TEMPERATURE: 

CONTROL OUTPUT: 

ALARM OUTPUT: 

RAMP OUTPUT: 

ANALOG INPUT: 

DIGITAL INPUTS: 

115/220/240 (optionally 208V), 50/60 Hz. 

0 - 40 oC 

INTRODUCTION 

Zero voltage crossing optically isolated SCR or Triac 

driver. On state RMS current 100mA max. 

Relay o/p, contact rating max 240V, 0.5A 

TTL Buffered Output. (optionally open collector) 

0 - 5V, corresponding to 0 - 1000 oC below setpoint 

(zones 1, 2 and 3 only). Used for calibration. 

4 TTL inputs for selecting recipe numbers (only for use 

without DPC) 


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 



only if the digital select input is connected to the digital 0 during a restart of the program. 

The digital inputs are used to select the recipe number. This information is coded in binary as 

follows. 

Recipe 0 

Recipe 1 

Recipe 2 

Recipe 3 

Recipe 4 

Recipe 5 

Recipe 6 

Recipe 7 

Recipe 8 

Recipe 9 

Recipe 10 

Recipe 11 

Recipe 12 

Recipe 13 

Recipe 14 

Recipe 15 

Pin 16 Pin 15 Pin 14 Pin 13 

1 

1 

1 

1 

1 

1 

1 

1 

0 

0 

0 

0 

0 

0 

0 

0 

1 

1 

1 

1 

0 

0 

0 

0 

1 

1 

1 

1 

0 

0 

0 

0 

When the furnace is running profile or normal recipes, the digital inputs can be used to select 

the number (0 - 15). 

2.2.3 Microprocessor Board 

The hub of the system is a Motorola CMOS 8-bit microprocessor. The on-board timer is 

used for all the timing functions. This board has one socket housing the functional EPROM 

and three sockets for the (8 Kb) memory chips. The processor board is equal for DTC and 

DPC, the functional EPROM and the amount of memory chips define the function of the 

processor board. 

For a DTC processor board a DTC EPROM and 1 memory chip is sufficient (for a DPC 

processor board a DPC EPROM and 3 memory chips are required). 

DIGITAL TEMPERATURE CONTROLLER REFERENCE MANUAL 2-2 

1 

1 

0 

0 

1 

1 

0 

0 

1 

1 

0 

0 

1 

1 

0 

0 

1 

0 

1 

0 

1 

0 

1 

0 

1 

0 

1 

0 

1 

0 

1 

0


Communication between the DTC and Touchscreen goes via the DPC communication 

boards. 

The processor board is provided with an automatic restart circuit. If the microprocessor 

stops for more than 5 seconds, the power supply supervisor will generate a reset signal. 

Figure 2-1 Jumpers position at processor board 

This board also contains a set of 5 jumpers to select the number of control zones for 

diffusion and conveyor furnace and the type of thermocouple. The possible configurations 

are shown below: 

• Selection of number of control zones 

3 diff 5 diff 6 diff 2x3 diff 6 conv 9 conv 12 conv 15 conv 

• Selection of Thermocouple type 

PtRH 13% PtRH 10% Platinel II Nich-Ni 

2.2.4 Communication board 

The DTC communication board provides optically isolated serial communication between 

DTC and DPC using a RS422 protocol at 9600 baud through a 10-pole connector. 

2.2.5 Output board 

The DTC output board sends the output signal from the processor board to the SCR 

interconnection board. 3 LED’s indicate the output level and should blink at least once per 

second. 


2.2.6 Power Supply board 


The power supply board generates the required +12, -12, +5 and -5 V that is required for the 

DTC. 

2.3 Hardware Temperature Control Loop 

2.3.1 Input circuit 

Preamplifier: The thermocouple signals are amplified on the 3-channel input boards in 

separate preamplifiers. The main components of these preamplifiers are a chopper stabilized 

operational amplifier, an open loop voltage gain amplifier and a 1 Hz filter and buffer. 

The chopper amplifier amplifies the low-level input first. The operational amplifier following 

the chopper amplifier increases the open loop voltage gain, to give an accurate and linear 

voltage gain over the complete input range. The 1 Hz filter limits the bandwidth of the 

preamplifier. This filter and the buffer are switched before the feedback resistor point. This 

eliminates errors introduced due to the leakage of the filter capacitors and the offset voltage 

of the 741 op-amp. 

Each 3-channel input board has one cold junction compensator circuit. The temperature at 

the cold junction is measured by a transducer, which produces an output current of 1 µA/K. 

This results in an output voltage from the amplifier of 33.9mV/ oC. After passing through a 

resistor divider, this becomes the correct cold junction compensation voltage for every 

amplifier. 

The output voltage of each preamplifier is 0 - 10V, corresponding to an input range of 0 - 

1500 oC for a PtRh 13% (type R) thermocouple. 

The input impedance is 4 K Ohm and to assure the mV source does not drop in voltage 

during measurement it should have an output impedance of 0.1 Ohm. 

A-D Conversion: The output voltage from the preamplifier is multiplexed and converted on 

the 16-channel A-D converter board. Fifteen channels of the 16 channel multiplexer are used 

for a maximum of 15 temperature-input signals, the remaining one being for the analog input 

from the rear connector. The channel to be converted is selected by the microprocessor 

setting the PA0-PA3 outputs of the PIA (Peripheral Interface Adapter). 

2.3.2 Output circuit 

A zero voltage crossing, optically isolated driver is used to fire the SCRs or triacs. The RMS 

(Root Mean Square) on state current is 100mA. 

Each output channel has an open/short circuit failure detector. The detector circuit measures 

the voltage across the SCRs or triacs via an optically coupled isolator and is connected to the 

common input bus line through an open collector NAND gate. A Power Alarm will be 

generated if the detector circuit detects a SCR failure. 

2.4 Software Temperature Control Loop 

The spike control loop on the spike thermocouples is the same for all zones. The control is 

proportional, integral and differential (P.I.D) and gain control is provided for limiting the 

power to the heating elements. 



A maximum of six zones can have paddle control on the paddle thermocouples. The control 

is differential, integral (D.I) on the paddle, which is cascaded on the spike thermocouple. In 

this type of control, there are 6 control blocks with 6 unique parameters. For each parameter, 

there are 5 distinct temperature ranges in steps of 300 oC. 

A block diagram of the control loop is shown in Figure 2-3. 

2.4.1 Spike Control 

The inputs for the spike P.I.D. control are the spike thermocouple reading, spike setpoint 

and spike P.I.D. parameters. The spike setpoint is calculated from the profile table. If the 

setpoint is not given in the table, the value can be obtained by interpolation. 

2.4.1.1 Spike derivative block 

The derivative control is used to make immediate changes, whenever the thermocouples 

readings change. The output of the block is proportional to the slope of the temperature and 

the derivative parameter. Hence, an increase in the derivative parameter will increase the 

effect of the derivative function. 

The input to this block is the thermocouple reading and not, as in most systems, the 

deviation between the setpoint and the reading. It is, also, switched off before the P.I. control 

blocks. The effect of these two actions on the ramping is shown in Figure 2-2. As can be 

seen the overshoot is greatly reduced. The deviation between setpoint and temperature 

during ramping is equal to the Derivative Output (DO = slope x parameter). 

The inputs to this block are the current spike thermocouple reading and the derivative 

parameter in seconds. The spike derivative value is an average of different spike 

thermocouple readings taken over a period of time. This gives a slope or trend to the 

movement of temperature in units/s. 

The spike derivative output is the derivative value multiplied by the spike derivative 

parameter in units of degrees. This value added to the setpoint deviation (setpoint reading) 

gives the P.D. output. The P.D. output is limited to plus or minus the proportional band 

output. 

Figure 2-2 Ramping comparisons 


Figure 2-3 Software temperature control loop 



2.4.1.2 Spike integral block 


The integral control block brings the temperature back to the setpoint. If there is an error, 

this block will make long term adjustments to the power. An increase in the integral 

parameter will decrease the amount of change in the (current controlling) output. 

The inputs to this block are the P.D. output and the Integral parameter. Every second the 

P.D output is divided by the Integral parameter value. This is then added to or subtracted 

from the integral output, depending on the sign of the input. The maximum value is equal to 

the proportional band value and the minimum is zero. This final value is added to the P.D. 

output to give the D.I. output. 

2.4.1.3 Spike proportional block 

The proportional control is used to create a bandwidth around the controlling setpoint. The 

proportional parameter will be the bandwidth at which maximum power will be applied. 

Proportional control always gives an offset between setpoint and actual temperature. This 

offset is needed to apply the power and is dependent on the proportional parameter and the 

amount of power needed to maintain the power. If the proportional bandwidth is too small, 

oscillation of the control loop can occur. 

The inputs to this block are the D.I. output and the proportional parameter (in degrees). The 

output is obtained by dividing the D.I. output by the proportional parameter and then 

multiplying by 100. This gives a percentage output (P.I.D). 

2.4.1.4 Spike gain block 

The gain block limits the maximum output power and is used to stop the controller 

oscillating. This is of particular importance at low temperatures. The control loop gives the 

best response if the power required to maintain the temperature is 35-45% of the maximum 

power. 

This block converts the percentage P.I.D. output into a scale related to the gain parameter 

value. During the ramping up of a zone, the gain parameter extracted from the parameter 

table is increased in relation to the slope of the ramp. If the temperature is below setpoint, 

the gain value is increased to compensate for the deficiency. The maximum value of the gain 

parameter is 98. 

2.4.1.5 Main and side zone gain blocks 

The main and side zone gain blocks are used for broadband conveyor furnaces. The three 

gain blocks translate the gain controlled PI.D output into three gain controlled power 

outputs. The input multiplied by the programmed gain value of the control zone divided by 

one hundred gives the current power output value. The maximum power value is 98%. The 

output is converted to proportioned on-off for the SCR or triac drivers. 

2.4.2 Paddle control 

The paddle D.I. control is only active if the zone is programmed for control on the paddle 

thermocouple and is only of interest in a diffusion furnace. The output of the D.I. control is 

used to modify the setpoint for the spike control loop. These modifications will be in 

response to the temperature variations inside the tube. 


2.4.2.1 Paddle derivative block 


The derivative block is the same as for the spike thermocouple. The temperature response 

inside the tube has a delay compared to the response outside the tube. This control loop will 

automatically give the necessary delay to the ramping, when the paddle derivative parameter 

value is greater then the spike derivative value. 

The inputs to the paddle derivative block are the paddle thermocouple reading and the 

paddle derivative parameter (in seconds). The paddle P.D. output is the sum of the derivative 

output and the paddle setpoint deviation (setpoint reading). The output is limited to plus or 

minus the proportional band value. 

2.4.2.2 Paddle integral block 

The integral block is used to make slow adjustments to the spike setpoint to bring the paddle 

temperature back to the setpoint. An increase in the paddle integral parameter will decrease 

the amount of change in the current spike setpoint. To prevent oscillation, the setpoint 

change per second must not exceed the maximum cooling or heating rate of the control 

zone. The feedback from the spike P.D. output results in no correction, if the deviation on 

the spike and paddle are equal in the same direction or when the deviation on both is out of 

the proportional band. 

The inputs to this block are the difference between the P.D. outputs of the paddle and spike 

blocks and the paddle integral parameter (in 0.1 minutes). The feedback from the P.D. output 

of the spike is used to dampen the cascaded control. The paddle integral output is limited to 

200 oC. The D.I. output is added to the spike setpoint calculated from the profile table, 

which gives the new setpoint for the spike control. 


3.DTC Configuration 

3.1 Introduction 

DTC CONFIGURATION 

The units that can be combined to give the desired configuration are shown in Figure 3-1. All 

systems have to contain the Controller Unit and the Touch Screen Display. 

3.2 Diffusion furnaces 

All Diffusion Furnaces require a data input unit (Touchscreen or TSC-II). The Controller 

Unit is also required, but it must be configured according to the type of furnace to be 

controlled. This dependents on the number of input and outputs required. 

3.2.1 Furnace with DPC 

The DTC Controller Unit is configured with two or four input boards and one or two output 

boards, giving control of up to 6 zones. Automatic Profiling and paddle control is possible if 

one (or two) of the input boards is placed in position E (and D). 

Communication to the DPC is provided by the communication board. It allows reception of 

temperature recipe selections from the DPC and provides temperature information to the 

DPC. 

The temperature can be ramped in each zone, either independently or under master/slave 

control (see section 3.4). 

3.2.2 Stand-alone 

The DTC Controller Unit is configured with two or four input boards and one or two output 

boards, depending on the tube configuration (3, 5 or 6 zones). For Automatic Profiling or 

control on the paddle thermocouples, a board has to be placed in position ‘E’ (Figure 3-1 

DTC Configurations) for the first 3 zones and position ‘D’ for the zones 4, 5 and 6. Boards 

for the spike are in position ‘A’ for the first three zones and ‘B’ for the next. 

In this configuration, the DTC controls the temperature in all zones of the furnace tube. The 

temperature can be ramped in each zone, either independently or under master/slave control 

(see section 3.4). The unit can store and run a maximum of 16 recipes. 

3.2.3 Furnace with source furnace, stand-alone 

The DTC Controller Unit is configured with three input boards and two output boards, 

giving control of 6 zones (3 in the main furnace and 3 in the source furnace). Automatic 

Profiling and paddle control is possible if one of the input boards is placed in position E. 

All the zones may be automatically profiled or paddle controlled. The temperature can be 

ramped in each zone of the main furnace and source furnace, either independently or under 

master/slave control (see section 3.4). 


Figure 3-1 DTC Configurations 



3.3 Conveyer furnaces 


All Conveyor Furnaces require the Controller Unit and either the Program and Display Unit 

or the Touch Screen Display . The difference in configuration depends on the heated length 

(number of control zones) and the width of the zones (whether or not side zone control is 

used). This will not only affect the number of boards in the Controller Unit, but also the type 

of Output Expander Unit used and the number of boards therein. If zones 13, 14 and 15 are 

not used as control zones, they can be used for profiling or temperature measurement. 

3.3.1 Small band conveyors 

The system configuration is solely dependent on the number of control zones used: 

a) For 1 to 6 Control Zones 

The system will consist of the Controller Unit and the Program and Display Unit or 

the Touch Screen Display , containing one or two, 3 channel input boards and one 

or two, 3 channel output boards. The number of input boards will be the same as 

the number of output boards. 

For example: To control 2 zones, one input board and one output board is necessary. 

b) For more than 6 Control Zones 

Besides the Controller Unit fitted with an Output Expander Interconnection board 

and the Program and Display Unit or the Touch Screen Display. An Output 

Expander Unit A has to be added to the configuration. The Controller Unit will 

contain the appropriate number of input boards (1 board for every 3 control zones) 

and an Output Expander Interconnection board placed in the first output board slot. 

The Output Expander Unit A will contain between 3 and 5 output boards depending 

on the number of control zones. There must be the same number of input and 

output boards. 

3.3.2 Broadband conveyors 

For the broadband conveyors or small band conveyors with accurate crossbelt temperature 

control, gain control on the two side zones is needed. The system requires the Controller 

Unit fitted with an Output Expander Interconnection board and either the Program and 

Display Unit or the Touch Screen Display;, and the Output Expander Unit B. The 

differences in configuration stem from the number of control zones used. 

a) For 1 to 9 Control Zones 

The Controller Unit is fitted with one to three input boards (1 board for every 3 

control zones). Output Expander Unit B contains an output board for each zone, 

which triggers the main zone and it's 2 side zones. 

b) For more than 9 Zones 

The Controller Unit is fitted with four or five input boards (1 board for every 3 

control zones). Output Expander Unit B contains the maximum nine output boards. 

It is, therefore, necessary that Output Expander Unit C is used, containing one 

board for each zone greater than nine. 


3.3.3 Recipes 


As of DTC version 2.I an unlimited amount of temperature recipes can be stored. Older 

DTC’s can store a maximum of 16 recipes. The recipes can be selected manually with the 

Touch Screen or TSC-II or automatically via the DPC or by using the digital inputs on the 

rear connector if no DPC is present. 

All the zones include ramping as part of the recipes, thus ensuring the temperature rises at a 

controlled rate. This prevents furnace, tube or muffle damage due temperature shock. An 

external timer can switch the DTC from one recipe to another. This can be used as an energy 

saving feature that allows the temperature of the furnace to be lowered at nights and 

weekends. 

3.4 Independent or Master/Slave Control 

The control zones normally operate in the Independent (I) mode. In this case, all the zones 

are completely independent of each other. However, the possibility exists to operate four or 

five zones (Slaves) under the control of another (Master). This is known as Master/Slave 

Control (MS). In this configuration the center zone (2 in a 3-zone furnace, 3 in a 5-zone 

furnace) is the master. 

All other zones operate normally as if they were independent zones. However, if during a 

ramp up or a cool down the master cannot follow its temperature setpoints, the Master/Slave 

loop becomes active. The deviation of the master from its setpoints is subtracted from the 

temperature setpoints of the slaves. This results in the same actual temperature for all three 

zones. 

When the furnace is not ramping, the Master/Slave loop becomes active if the deviation 

from the setpoints in the master is greater than 5 ºC. 

This configuration will only work correctly if the master is slower than the slaves. If this is 

not the case, either the gain value of the slaves has to be increased or the gain value of the 

master has to be decreased. 

A comparison of the zone temperatures for both types of control is given in Figure 3-2. 

Figure 3-2 Independent and Master/Slave control 


4.Installation and Calibration 

4.1 Installation 

INSTALLATION AND CALIBRATION 

STEP 1: 

The Digital Temperature Controller, once configured correctly, is mounted on the side of the 

furnace. The DTC is installed prior to delivery. Before applying the line voltage to the unit 

check if: 

a) The local line voltage meets the specified conditions for your particular controller. 

b) The SCRs or triacs are wired to the interconnection board SCR stand. 

 

NOTE 

Wiring the SCRs incorrectly could cause serious damage to the DTC 

output board. 

c) The jumpers on the processor board are set correctly for the number of control 

zones and type of thermocouple being used (see section 2.2.3). 

STEP 2: 

After the above checks are made, the line voltage can be applied to the controller. 

Before programming the controller the user should wait 10 seconds, during which time any 

alarms generated by the control zones will be displayed. 

The unit should now be calibrated as described in the next section. 

4.2 Calibration 

At the time of delivery, the DTC has been calibrated for accurate operation. However, it is 

advisable to repeat the cold junction board calibration of section 4.2.3. To ensure the 

continued accuracy of the controller the entire calibration procedure should be carried out at 

regular intervals indicated in the maintenance schedule. 

4.2.1 Equipment required 

The following standard laboratory equipment is required to calibrate the controller. 

a) 5 Digit DC Digital Voltmeter. 

b) Precision Power supply - Resolution 1 µV 

c) Ambient Temperature Thermometer. 


4.2.2 Analog-to-digital converter board 


The Analog to Digital Converter board is calibrated using the analog input on the rear 

connector of the Controller Unit (see Figure 4-1). 

Figure 4-1 Converter Card and Rear Connector 


STEP 1: 


If the analog input (pin 18 of the rear connector) is in use, disconnect the wiring. If it is not 

in use, connect the analog select input (pin 9) to digital 0 (pin 11). Switch off the line voltage 

momentarily to make the analog input active. 

STEP 2: 

Short the analog select input (pin 18) to the analog 0 (pin 17). 

STEP 3: 

Program into zone A2 a temperature setpoint of 1100.0 oC. See DTC operating manual or 

Touch Screen Display manual for programming instructions. 

STEP 4: 

Select Display of the paddle setpoint for zone A2. 

STEP 5: 

Place the probes of the Digital Voltmeter on the test points tp 1 and tp 2 of the board and 

adjust R13 to give a reference voltage of 10.00V. 

STEP 6: 

Turn R12 (zero adjust) clockwise until the setpoint reading starts to decrease. Then turn R12 

slowly counter-clockwise until the setpoint reading is 1100.0 oC. 

STEP 7: 

Remove the short circuit on the analog input and apply an input voltage of 5.000V to the 

analog input (pin 18) with respect to analog 0 (pin 17). Adjust R11 (gain adjust) to give a 

setpoint reading of 100.0 °C and repeat step 5. 

STEP 8: 

If the analog input is used, reconnect the analog input to the system. If the analog input is 

not used, disconnect the short between the analog select input (pin 9) and digital 0 (pin 11) 

and turn off the line voltage momentarily to make the analog input inactive. 

4.2.3 Channel input board with cold junction board 

The calibration of this board should not be attempted until the user is certain that the Analog 

to Digital Converter board is correctly calibrated. See Figure 4-2 for the position of the 

potentiometers. 

STEP 1: 

Display the three actual temperatures of the input board. 

STEP 2: 

On the Cold Junction Board short the inputs to the three thermocouple inputs. 

STEP 3: 

Adjust R26 (R25, R24 (zero adjust)) of the preamplifiers until they all show the same reading 

on the display. 


Figure 4-2 Channel Input Card 

STEP 4: 


Measure the ambient temperature around the point at which the thermocouple inputs are 

shorted. Adjust R23 so that the displayed reading is equal to the measured ambient 

temperature. 

STEP 5: 

Apply an input voltage to thermocouple input 1 corresponding to 1300 oC for a PtRh 6%, 

10% and 13% thermocouple or 1100 oC for a Platinel II or type K thermocouple. For type B 

an exception has to made. Because of the less voltage under 400 0C, the adjustment for 0 can 

not be done by ambient temperature, but needs to be done by 400 0C. 


NOTE 


Make sure any reference to calibrated paddle thermocouples has been 

removed from the DTC configuration. Failure to do so will results in false 

adjustments and incorrect calibration. 

The required input voltage dependents on the type of thermocouple and the ambient 

temperature around the point at which the input voltage is connected. The input voltage in 

the following table gives the millivolts at calibration temperatures at different ambient 

temperatures: 

Ambient Temperature 

Millivolt at calibration temperature at different ambient 

temperartures 

1100.000 1300.000 1300.000 1300.000 400.000 1100.000 

K R S B B PT2 

0 45.119 14.629 13.159 7.848 0.787 45.354 

18 44.401 14.529 13.058 7.851 0.790 

19 44.361 14.524 13.052 7.851 0.790 

20 44.321 14.518 13.046 7.851 0.790 

21 44.281 14.512 13.040 7.851 0.790 

22 44.240 14.506 13.034 7.851 0.790 

23 44.200 14.500 13.028 7.851 0.790 

24 44.159 14.494 13.022 7.851 0.790 

25 44.119 14.488 13.016 7.850 0.789 

The ambient temperature value can be obtained from standard tables. In the following table 

the millivolt at different ambient temperatures are given. These are used to calculate the 

millivolts at calibration temperature in the previous table. 

Ambient Temperature 

Millivolt at different ambient temperatures 

K R S B PT2 

0 0 0.000 0.000 0.000 

18 0.718 0.100 0.101 -0.003 

19 0.758 0.105 0.107 -0.003 

20 0.798 0.111 0.113 -0.003 

21 0.838 0.117 0.119 -0.003 

22 0.879 0.123 0.125 -0.003 

23 0.919 0.129 0.131 -0.003 

24 0.960 0.135 0.137 -0.003 

25 1.000 0.141 0.143 -0.002 


STEP 6: 


Adjust R22 (R21, R20) to give a reading of 1300.0 oC for PtRh 6%,13% and 10% and 

1100.0 oC for Platinel II and type K. 

STEP 7: 

Repeat steps 5 and 6 for zone 2 and 3, adjusting R21 and R20, respectively, in step 6. 

 

NOTE 

Steps 1 to 4 of the above mentioned calibration procedure should be 

repeated for every cold junction board present. 


4.3 Repair 


Qualified personnel only should carry out repair. If the necessary qualified personnel are not 

available, the defective controller or module may be returned to the field service office of 

Amtech/Tempress Systems. 

It is recommended that spare boards and/or modules are kept in stock so a faulty board can 

be quickly replaced. This will give the shortest possible down time. The faulty board can then 

be repaired offsite. 

Most parts are widely available and should be obtainable from local suppliers. However, it is 

important that replacement parts comply with the value, tolerance, rating and dimensions 

specifications given in the parts list. 

Prior to soldering on any printed circuit board make sure that all power to that board is 

disconnected. After soldering, the board should be thoroughly cleaned with particular 

attention being given to the removal of fluxes and chemical residues. 

Repairs to the Cold Junction board or preamplifiers on the input board should be done with 

great care, maintaining the original conditions as close as possible. 

After a repair to the analog circuitry, the instrument should be re-calibrated.

Digital Temperature Controller Reference Manual

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