SECTION
I
General Information
1.1
Introduction
The following is a description of the DRC-84C Cryogenic Digital
Thermometer/Controller. The DRC-80 Series of instruments is designed to be
used with the Model DT-500-DRC and DT-500CU-DRC-36 silicon diode sensors
manufactured by Lake Shore Cryotronics, Inc.
Several different diode sensor curves are designed for use with this
instrument. When ordering replacement sensors, care must be taken to assure
that the correct sensor curve is specified. Multiple curves are needed
so
that Lake Shore can assure the customer that replacement sensors
will
be
available at any time in the future. For details, please see Section 1.4.
This controller
will
also use the PT-101,
102,
103 Series of platinum
resistance thermometers which are available from Lake Shore Cryotronics,
Inc. The data sheet for these sensors is included in the back of this manual.
1.2 Description
The DRC-80 Series is comprised of completely self-contained units
providing direct digital readout in Kelvin temperature units and, for the
controllers, temperature control by direct analog comparison between the
sensor voltage and an analog equivalent of the digital temperature set point.
The Lake Shore DRC-84C utilizes two temperature sensor technologies to
achieve its wide range: Silicon diodes for the low range (1.4-330K), and
platinum RTD's for higher temperatures (30-800K). Each sensor type has its
own input section which contains appropriate sensor excitation sources,
signal conditioning, and switching.
A
microprocessor
in
the 84C determines
the temperature based on the input section activated, the sensor signal, and
the sensor-response curve stored in internal memory. Additionally, the micro-
processor generates a voltage equivalent to the control set-point temperature
for the sensor in use. Comparison of that voltage with the actual sensor
voltage produces the error signal which is the basis
of
the 84C's analog
control.
Each input section of the DRC-84C features dual-sensor input which
enables two sensors to be used concurrently. Either sensor can be selected
to be the control sensor and/or the temperature display sensor (both sensors
must be of the same type
-
silicon diodes or platinum RTD's). Thus control
can be centered at one point
in
a system and temperature monitored elsewhere.
This permits, for instance, maintenance of temperature at a particular cold
stage and simultaneous measurement of sample temperature. Selection of input
section as well as display and control sensor is made via front-panel push-
but tons.
-1-
To Next Page
Loading...