The Systems Laboratory Temperature Sensing Test Bed, type SL20, is part of
the modular system for teaching the use and applications of transducers,
measurement systems and signal processing techniques.
The SL20 Test Bed is intended for use with the Systems Laboratory
Mainframe, SL1, and the user is referred to the SL1 Mainframe manual itself
for further information.
The SL20 Temperature Sensing Test Bed illustrates techniques of sensing and
control of temperature. Component parts of the Test Bed are covered in more
detail in later sections but the operation of the Test Bed can briefly be
described as follows:
The Test Bed itself is mounted on a sturdy sub-chassis which fits into place on
the upper deck of the Mainframe and is located on studs. Mounted on top of
the sub-frame is the heating system which can be used to increase the temperature of various thermostat devices on the sub-chassis and can be
controlled by the thermal sensing devices themselves.
The major heating system is made up of two 100 Watt reflector heating lamps.
Although these lamps are supplied from full mains voltage, they are
controlled via a relay with a 12V coil so that all signal and transducer
connections are at a low voltage.
In addition to providing the heating source, the lamps also serve as a
convenient indication that the heating power is on. The heat generated by the
bulbs can be used to warm up various sensing devices mounted directly on
top of the sub-chassis.
The devices available include:-
Simple bimetallic fixed temperature controller with temperature
indicating thermocouple.
A presettable bimetallic strip controller with anticipatory heater and
temperature measuring thermocouple.
A bulb and capillary thermostat with temperature indicating
thermocouple.
Also available are two magnetic thermal sensing devices excited by a separate
heating coil. One works on the Curie effect of loss of magnetism with
temperature and the other on the Hall effect sensing magnetism with
temperature.
All of the connections to the various transducers, thermocouples and
controller relays are brought out to a series of 2mm sockets which are
arranged on the front of the Test Bed with descriptive legends of their various
functions.
All signal connections are made via these sockets and no connections either
power, signal or otherwise are made automatically when the Test Bed is
placed on the Mainframe. The Mainframe simply serves as a convenient
mounting system for the Test Bed assembly which is itself totally self
contained. This SL20 Temperature Sensing Test Bed forms a part of the Systems
Laboratory complex, which includes the SL1 Mainframe and various test beds
covering other types of physical measurement system. Plug in signal
processing modules may be selected and interchanged as appropriate to the
measurement task in hand.
Later sections of this manual will describe in detail the function and operation
of the parts of the SL20 Temperature Sensing Test Bed and will consider the
Mainframe and those electronic signal processing modules which are
necessary for use with the transducers in this measurement system.