Lake Shore DRC-70 User manual

User’s Manual
Model DRC-70
Digital CryogenicThermometer
Model DRC-7C/-70C
Digital CryogenicController
Obsolete Notice:
This manual describes an obsolete Lake Shore product. This manual is a copy from our
archives and may not exactly match your instrument. Lake Shore assumes no responsibility for
this manual matching your exact hardware revision or operational procedures. Lake Shore
is
not responsible for any repairs made to the instrument based on information from this manual.
Lake Shore Cryotronics, Inc.
575 McCorkle Blvd.
Westerville, Ohio
43082-8888 USA
E-MailAddresses:
[email protected]
[email protected]
Visit Our Website:
www.lakeshore.com
Fax: [phone]
Telephone: [phone]
Methods and apparatus disclosed and described herein have been developed solely on company funds of Lake Shore Cryotronics, Inc.
No government or other contractual support or relationship whatsoever has existed which in any way affects or mitigates proprietary
rights
of Lake Shore Cryotronics, Inc. in these developments. Methods and apparatus disclosed herein may be subject to US. Patents
existing or applied for. Lake Shore Cryotronics, Inc. reserves the right to add, improve, modify,
or withdraw functions, design
modifications, or products at any time without notice. Lake Shore shall not be liable for errors contained herein or for incidental or
consequentialdamages
in connection with furnishing, performance, or use of this material.
Obsolete Manual
October 1979

WA R R A NTY
LAKE SHORE CRYOTRONICS, INC. warrants each instrument of
its own manufacture to
be free from defects in material
and workmanship. Obligations under this Warranty shall
be limited to replacing, repairing
or giving credit for
the purchase price, at
our option, of any instrument ret-
urned, shipment prepaid,
to our factory for that purpose
within ONE year of delivery to the original purchaser,
provided prior authorization for such return has been
given by an authorized representative of Lake Shore Cryo-
tronics, Inc.
This Warranty shall not apply to any instrument, which our
inspection shall disclose to our satisfaction, to have
become defective or unworkable due to abuse, mishandling,
misuse, accident, alteration, negligence, improper installa-
tion,
or other causes beyond our control. This Warranty
likewise shall not apply to any instrument or component
not manufactured by others and included in Lake Shore Cryo-
tronics, Inc. equipment; the original manufacturer's warran-
ty
is extended to Lake Shore Cryotronics, Inc. customers.
Lake Shore Cryotronics reserves the right to make changes
in design at any time without incurring any obligation
to install same on units previously purchased.
THERE ARE NO WARRANTIES WHICH EXTEND BEYOND THE DESCRIPTION
ON THE FACE HEREOF. THIS WARRANTY IS IN LIEU OF, AND
EXCLUDES ANY AND ALL OTHER WARRANTIES OR REPRESENTATIONS,
EXPRESSED, IMPLIED OR STATUTORY, INCLUDING MERCHANTABILITY
AND FITNESS, AS WELL AS ANY AND ALL OTHER OBLIGATIONS,
LIABILITIES OF LAKE SHORE CRYOTRONICS, INC., INCLUDING
BUT NOT LIMITED
TO, SPECIAL OR CONSEQUENTIAL DAMAGES. NO
PERSON,
FIRM
OR CORPORATION IS AUTHORIZED TO ASSUME FOR LAKE
ITY NOT EXPRESSLY PROVIDED FOR HEREIN EXCEPT IN WRITING DULY
EXECUTED BY
AN OFFICER OF LAKE SHORE CRYOTRONICS, INC.
SHORE CRYOTRONICS, INC. ANY ADDITIONAL OBLIGATION OR LIABIL-

Table of Contents
Section Page
I. General Information
1.1 Introduction 1
1.2 Description - General 1
1.3 Description - Specific 2
1.3.1 General Specifications 2
1.4
Major Assemblies Supplied 4
1.5 Accessory Equipment and Custom Options Available 4
1.6 Ordering of Replacement or Additional Sensors 4
II. Installation
2.1 Introduction 6
2.2 Initial Inspection 6
2.3 Power Requirements 6
2.4 Grounding Requirements 6
2.5 Installation 6
2.6 Repackaging for Shipment
8
III. Operating Instructions
3.1 Introduction
9
3.2 Controls, Indicators, Connectors 9
3.3 Temperature Readout
15
3.3.1 Remote Parallel BCD Input/Output Option 15
3.4
Standard DT-500-DRC and DT-500CU-DRC-36 Curves 16
3.5 Calibration of the DRC-70/7C/70C Display 16
IV. Theory of Operation
4.1 Introduction 21
4.2
General Description 21
4.3
Detailed Description 21
4.3.1
Power Supplies 21
4.3.2
Precision Current Source 24
4.3.3
A/D Converter 24
4.3.4
Microprocessor Hardware 24
4.3.5
Software 25
4.3.6
Digital Display Board 31
V. Troubleshooting
5.1 Introduction 33
5.2 Test Equipment and Accessories 33
5.3
General Remarks 33
5.4
Instrument Tests 33
VI. Parts List and Schematics
6.1
DRC Series Parts List and Schematics 40
VII. Appendices

Table of Illustrations
Reference Description Page
Figure
1.1 Model DRC-70 Digital Cryogenic Thermometer iv
Figure 1.2 Model DRC-70C Digital Cryogenic Thermometer/
Controller
V
Figure 2.1 Sensor Cable Diagrams 7
Table 3.1 Entry Number Correlation 9
Figure 3.1 DRC-70 Front Panel 11
Figure 3.2 DRC-70 Rear Panel 12
Figure 3.3 DRC-7C/70C Front Panel 13
Figure 3.4 DRC-7C/70C Rear Panel 14
Table 3.2 BCD Temperature Output - Remote I/0 17
Table 3.3 DT- 5 00-DRC Voltage - Temperature
Characteristic
18
Figure 4.1 Block Diagram of DRC-70 22
Figure
4.2 Block Diagram of DRC-70C 23
Figure 4.3 Flow
Chart of DRC-Software 26
Figure
4.4 Control Gain Function 30
Figure
4.5 Control Integral Function 30
Table
5.1 DRC Signals and Functions 34
Figure 5.1
DRC Component Waveforms 36
Table 5.2
Problem and Solution 38
Table 6.1
Model DRC-Series Circuit Board Components 40
Figure 6.1
DRC-Circuit Schematic 44
Figure 6.2 DRC-Component Layout
45
Figure 6.3 Display Board Schematic 46
Figure 6.4 DRC-L/A Option Schematic 47

SECTION I
General Information
1.1 Introduction
The following
is a description of the DRC-70 cryogenic digital
thermometer and
DRC-7C, DRC-70C cryogenic digital thermometer/controllers.
The DRC-7/70 series of instruments are 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 1.6.
1.2 Description-General
The DRC-7/70
series are comprised of completely self-contained units
providing direct digital readout in kelvin temperature units and, for the
controllers, temperature control by direct digital comparison between the
displayed temperature, and a digital setpoint. The DRC-70 and DRC-70C display
temperature to
0.1 kelvin resolution while the DRC-7C displays temperature
to
1 kelvin resolution.
The specified range
of operation is 4.0 to 400 K* utilizing standard
DRC series sensors which have been pre-selected to provide uniform character-
istics over this range. These sensors conform to the standard table (see
Table
3.3) to 0.5 R or better over this temperature range. The instruments,
however, are useful to
1 K although the accuracy is not guaranteed below 4 K.
Pre-selection allows the DRC-7/70 series to be used with the DT-500-DRC and
DT-500CU-DRC-36 sensors without adjustments of any kind. Since the standard
sensors
are interchangeable, the instruments may be used to read out any
number of sensors with equal accuracy when selected through an appropriate
switch or multiplexer.
All instruments contain a constant current source, for sensor excita-
tion, which
is preset at the factory at 10 microamps.
As a standard feature, all units are equipped with an analog output of
the sensor voltage. This allows the instrument user the ability to record the
sensor voltage versus
time or to use a digital voltmeter to measure the sensor
voltage directly. Since this output
is not buffered, a high input impedance
recorder or voltmeter must be used to avoid loading
of the sensor. If the
sensor
is calibrated by the user or by Lake Shore Cryotronics, Inc.,
temperature may be determined to better than
10mK.
Four options are available with the DRC-7/70 series of instruments.
One option
is an analog signal which is proportional to temperature (DRC-L/A).
This
is set up to have
a sensitivity of 10 mV/K but may be changed to the user's
needs. Another option
is a BCD output of the displayed temperature (DRC-BCD-0
for DRC-70 or
DRC-BCD-I/0 for the DRC-7C/70C). Included with the BCD output
*
If possible, temperatures above 330 K should be avoided with DRC series
sensors since some of these sensors may shift their values slightly below
20 kelvin if heated above 330 kelvin.

option for the DRC-7C/70C instruments is the capability to remote program
the temperature
set point via a BCD signal from sources such as a computer or
digital function generator. The third option
is either a two position, five
position, or ten position switch (DRC-SW-
2, 5, or 10) for multiple sensor
readouts. The DRC-70 has the switch mounted internally while the DRC-7C/70C
has the switch mounted in an external box. The fourth option
is a custom
cut PROM (Programmable Read Only Memory) which corresponds to the calibration
curve of the customers DT-500
series sensor. A combination of calibration and
custom cut PROM
will increase instrument accuracy to 0.1 kelvin. Please note
that any sensor may be used with this option,
i.e., the customer is not
restricted to the
DRC series sensors.
1.3 Description-Specif ic
The following provides a description for the DRC-70 and DRC-7C/70C
instruments.
The DRC-70 and DRC-70C provide direct temperature readout in kelvin
degrees with
0.1 degree resolution. The DRC-70C controls in a properly
designed system to
0.1 kelvin. The DRC-7C has 1 degree resolution and controls
to 1 kelvin. Conformity to a standard DRC curve is better than 0.5 kelvin
over the temperature range from 4.0 to 380
K.
The DRC-7/70 series is designed around an F8 microprocessor using a
3850/3853 configuration and associated support circuits. The DRC curve is
stored in a PROMwhich can handle up to 32 break points. The data consists
of a table of temperature, voltage and slope between each break point. These
straight line segments generate the
DRC curve to an accuracy of better than
0.1 kelvin over the entire temperature range (4.0 - 400 K). Sensors are
selected to conform to this curve to an accuracy of better than 0.5 K over the
entire range.
1.3.1 General Specifications
The following specifications for the DRC-7/70
series are applicable
when used with the standard DT-500-DRC or DT-500CU-DRC-36 temperature sensors.
General
:
Temperature Range:
1 to 400K (Accuracy not guaranteed below 4.0 K)
Sensor: Silicon Diode (Model DT-500-DRC or DT-500CU-DRC-36)
Sensor Input:
4 terminal connection, constant current excitation
Sensor Excitation: Constant current 10 microamperes
Current Regulation: ±0.01%
Input Line Voltage:
115 V or 230 V, 50 - 60 Hz, switch selectable
Operating Environment:
10 - 45°C
Circuit Design: Integrated circuits, microprocessor controlled

Input Impedance: Greater than 100 megohms
Weight:
5.9 Kg (13 pounds)
Dimensions: 10.7cm
(4.2") high x 31.0cm (12.2") wide x
25.4cm (10.01”) deep
Temperature Readout:
Display:
3 digits (for DRC-7C), 1.1cm (0.43") high, 7
segment, non-blinking
4 digits (for DRC-70/70C), 1.1cm (0.43") high, 7
segment, non-blinking
Temperature Coefficient
Error:
0.01 K/°C
Conformity To LSCI Standard
DRC-70 Silicon Diode Table:
0.5 K (4 - 400 K)
Resolution:
1 K for DRC-7C
0.1 K for DRC-70/70C
Response
Time: 2.2 seconds to rated accuracy
outputs
:
Analog (Standard): Monitor output of sensor voltage
Analog (Optional): 10mV/K
at <10 ohm output impedance
Digital (Optional):
TTL compatible parallel BCD
Temperature Control: (For DRC-7C/70C only)
Set Point: Digital thumbwheel selection directly in
kelvin temperature units
Set Point Resolution: 1 K for DRC-7C and 0.1 K for DRC-70C
Optional Remote Set Point:
TTL compatible, parallel BCD
Controllability: 1 K (for DRC-7C) with a properly designed system
0.1 K (for DRC-70C) with a properly designed system
Standard
0 - 46 watts, 0-1A, 0 - 46 VDC Heater Output:
Control Mode:
Time proportional gain and reset

1.4 Major Assemblies Supplied
The DRC-7/70 series includes as standard equipment, in addition to
the digital thermometer, the following:
A. Operating and Servicing Manual.
B. Five Pin Plug for Temperature Sensor Cables.
C. Three Pin Plug for Monitor of Sensor Output Voltage.
Model DT-500 series silicon diodes are not supplied as part of the
DRC-7/70 instrument.
1.5 Accessory Equipment and Custom Options Available
The following accessory equipment and custom options are available from
the factory. Items marked with an asterisk
(*) are of a custom nature, the customer
should discuss these items with a factory representative before ordering.
A. Extra Five Pin and Three Pin Connectors.
B. 19" Rack Mount.
C. DT-500-DRC and DT-500CU-DRC-36 Silicon Temperature Sensitive Diodes
(Uncalibrated). (See data sheets at end of this manual for nominal
operating characteristics and case styles available).
D. DT-500-DRC Silicon Temperature Sensitive Diodes (Calibrated). Standard
laboratory calibration service for correlating diode output voltage
with diode temperature.
ation. See sensor data sheet for additional inform-
E. Custom Modification of Sensor Current Supply Value.*
F. Analog of Temperature (10mV/°Kis standard).
G. TTL Compatible Parallel BCD of Temperature (Also Remote Set Point
Input
- Standard with BCD output for DRC-7C/70C instruments).
H. Custom Cut PROM of calibrated DT-500 diodes series.
I. Two Position, Five Position and Ten Position Switches for multiple
sensor readout. (Switch is mounted internally in DRC-70 instruments
(See Table
3.1)
instruments . )
Switch is mounted in an external box for DRC-7C/70C
1.6 Ordering of Replacement or Additional Sensors
Two different sensor configurations are available for use with the
Model DRC-7/70 series instruments. These are the DT-500-DRC and the DT-500-CU-
DRC-36 sensors. Their description is included in the cryogenic temperature
sensing elements brochure which is included in the back
of this manual (see
reference numbers
8 and 14 for dimensions of these sensors).
Three curves presently exist which can be used with the DRC series
instruments. The correct curve must be specified
so that your instrument
will have its stated accuracy.
following ways
:
The proper curve may be determined in one of the