Lake Shore DRC-84C User manual

User’s Manual
Model DRC-84C
Digital Cryogenic
ThermometerlControlIer
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.
LakeShoreCryotronics, Inc.
575 McCorkleBlvd.
Westerville, Ohio43082-8888USA
E-MailAddresses:
[email protected]
[email protected]
Visit OurWebsite:
www.Iakeshore.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 U.S. 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 inconnectionwith furnishing, performance,or use
of this material.
Obsolete Manual
April 1982

Table of Contents
Section
I. General Information
1.1 Introduction
1.2 Description
1.3 Major Assemblies Supplied
1.4 Ordering of Replacement or Additional Sensors
II. Installation
2.1 Introduction
2.2 Initial Inspection
2.3 Power Requirements
2.4 Grounding Requirements
2.5 Installation
2.6 Repackaging for Shipment
III. Operating Instructions
3.1 Introduction
3.2 Controls, Indicators, Connectors
3.3 Temperature Readout
3.4 Analog Control
3.5 Analog Output of Temperature
3.6 Standard DT-500-DRC and DT-500CU-DRC-36 Curves
3.7 The 10-Sensor Selector Switch
3.8
3.9
IEEE Interface Option
Remote Parallel
BCD Input/Output Option
3.9.1 General
IEEE Specifications and Operation
3.9.2 Specific Operation
of the DRC8-IEEE Interface
3.9.3 Sample Programming
3.10
3.11
3.12 Rack Mounting the DRC-84C
3.13 Error Conditions
Installation of
DRC BCD/L-A Option Board
Installation
of DRC IEEE Option Board
IV. Theory of Operation
4.1 Introduction
4.2 General Description
4.3 Detailed Description
4.3.1 Power Supplies
4.3.2
4.3.3
4.3.4 Software
4.3.5
4.3.6 Digital Display Board
Precision Current Sources and Input Switching
A/D Converter and Microprocessor Hardware
Analog Control and Set Point
Page
1
1
3
3
5
5
5
5
5
6
9
9
12
12
13
13
13
14
26
26
27
32
34
35
36
36
37
37
39
39
40
40
41
44
45
-ii-

Table of Contents (cont'd.)
Section
V. Calibration and Troubleshooting
5.1 Introduction
5.2
Test Equipment
5.3 General Remarks
5.4 Instrument Calibration
5.4.1 Current Sources
5.4.2
A/D Converter
5.4.3
D/A Converter
5.4.4 Output Buffer
5.4.5
DRC L/A Option (if present)
5.5 Instrument Tests
VI. Replaceable Parts List
6.1 Main Board Components
6.2 DRC-84C
BCD-L/A and IEEE Components List
Page
47
47
47
47
47
48
48
51
51
55
55
63
-iii-

Table of Illustrations
Reference
Figure
1.1
Figure 2.1
Table 3.1
Figure
3.1
Figure 3.2
Table 3.2
Table 3.3
Figure
3.3
Table 3.4
Figure 3.4
Table 3.5
Table 3.6
Table 3.7
Figure 4.1
Figure 4.2
Table 5.1
Table 5.2
Table 5.3
Table 5.4
Figure 6.1
Figure 6.2
Figure 6.3
Figure 6.4
Figure 6.5
Figure 6.6
Figure 6.7
Figure 6.8
Figure 6.9
Figure
6.10
Figure 6.11
Description
Model DRC-84C Digital Cryogenic
Thermometer/Controller
Sensor, Cable, and Monitor Connections
Entry Number Correlation
DRC-84C Front Panel
DRC-84C Back Panel
Relative Gain for
BCD Option
Reset Time Constants for BCD Option
DRC-84C-IEEE Panel Layout
DT-500-DRC Voltage-Temperature Characteristic
Model DRC-84C showing Rack Mount
Kit
SW-1OA Connector Detail
BCD Temperature Output - Model DRC-Series
DIN Standard Curve for Platinum Sensors
DRC-84C Block Diagram
Software Flow Diagram
Decimal-hex Table
Data for Standard Curves (D & E)
DRC-84C Troubleshooting Notes
DRC-84C Troubleshooting Notes
DRC-84C Power Supply
DRC-84C Current Source, Input Connections,
DRC-84C Microprocessor Section
DRC-84C Analog Output Section
DRC-84C Component Layout
DRC-84C Display Board
DRC-84C Display Board Component Layout
DRC-84C
BCD/L-A Option
DRC-84C
BCD/L-A Option Component Layout
DRC-84C
IEEE Option
DRC-84C
IEEE Option Component Layout
Remote
1/0
Switching
Page
7
9
11
11
15
16
28
17
35
20
21
22
38
43
49
49
52
53
67
69
71
73
75
77
77
79
79
81
81
-iv-

Specifications, DRC-84C Temperature Controller
Input: General:
Temperature Range:
1.4 to 330K with standard silicon Monltor Output: Buffered output of 1X Display Sensor
diode DRC Sensor
(to 380K with other silicon Sensors). voltage (silicon) and5X DisplaySensorvoltage (platinum).
30
to 800K with platinum sensor. Silicon diodes cannot Additional outputs listed below as options.
be exposed
to temperatures above their useful range.
Dimensions, Weight: 432mm wide x 102mm high x
Sensors (order separately): Silicon Diode: DT-500-DRC. 330mm deep (17 in
x 4 in x 13 in). Style L. full-rack
DT-500CU-DRC-36 or any calibrated DT-500 Series package. Net weight 8.4 kg (18.5 Ibs).
Diode (with DRC-Precision Option). See below for
power: 90-110, 105-125, or 210-250VAC. 50 or 60Hz.
proper response curve. Platinum RTD: PT-101. PT-102, 75 watts,
PT-103'
Or any Other 100-ohm, 0.00385/°c Sensor'
Accessories Supplied: Mating connectors for sensor
inputs and monitors, instruction manual.
See response curve details below.
Sensor Input: Two section input (silicon-diode and
platinum RTD). Front-panel switch selects either section.
Each section accommodates two sensors with 4-terminal
Options and Accessories Available:
input for each sensor. Front-panel switches enable Model DRC8-BCD. Parallel BCD interface, TTL com-
independent selection of either sensor within each patible. Allows remote control of set-point, gain,
section as display and/or control sensor. Display/control reset, and provides BCD
output of temperature in Kelvin
sensors cannot be mixed between silicon and platinum and Sensor selected (either from front-panel or optional
Sensor Excitation: Current source. 10, microamperes Model DRC8-IEEE. 488 interface. Allows remote control
for each sensor in silicon-diode section,
0.5 milliampere of set-point, gain, reset and provides digital output of
(±0.005%)for each sensor in platinum RTD section. temperature in Kelvin and Sensor selected (either from
Sensor ResponseCurves: Silicon Diode Section: Domes- front-panel or optional SW-10A)
.
tic US units require Sensor Curve "D". Export units Model DRC8-L/A. Analog output proportional to Kelvin
require Sensor Curve
"E". Sensor curves subject to temperature for use with recorders, or other readouts.
change, refer
to manual for proper curve when reorder- 10mV/K at<10 ohm output resistance.
ing Sensors. Curves
to match existing Sensors available Model KT-LA. Analog output identical to DRC8-L/A
on special request. See also DRC-Precision Option. except for use when unit is also equipped with DRC8-
Platinum RTD Section: Standard response curve is
BCD,
based on 0.1% interchangeability at 0°C and temp- Model KT-BCD. Parallel BCD interface identical to
erature coefficient (0-100°C) of O.O0385/"C. Refer DRC8-BCD except for use when unit is also equipped
to Lake Shore PT-100 Technical Data for details. with DRC8-L/A,
Special calibrations are available and may be incor-
porated into the 84C via the DRC-Precision Option.
Model SW-10A. 10-Sensor Selector Switch for use with
DRC Thermometer or Controller. Pushbutton selection
Input Resistance: Greater than 1000 megohms. Maxi- of any one of up to 10 sensors, Connects to Sensor "B"
position. Sensor selected is also identified via digital
mum Sensor Power Dissipation: Silicon-diode: 25µW
at 4.2K. Platinum: 25µW below 80K increasing
to 100µW interfaces. Dimensions: 216mm wide x 102mm high
x 330mm deep (8% in x 4 in x 13 in). Style L half-
at 273K. rack package.
Model RM-3F. Rack ears with handles to mount style
Temperature Readout:
Display:
4 digit, 1.1 cm (0.43") LED shows temperature
L full-rack instrument package in standard 3%" rack
directly in Kelvin or Celsius as selected by front-panel
space
switch. Display Sensor can be selected independent of
Model RM-3H. Rack mounting hardware to mount
either one of two Style L half-rack unit(s) in standard
Control Sensor within each section.
Resolution: 0.1K or 0.1°C. "Scale Expand" increases 3½" rack space,
resolution to 0.01K for temperatures below 30K and DRC-Precision Option: Custom-programmed read-
only-memory for DRC instruments which improves
0.05K for 30-100K (no increase in accuracy).
Accuracy (20-25°C ambient): Silicon-diode: ±0.5K at specified accuracy to ±0.1K or better over a given
4K and 77K. ±1.0K at 300K with standard sensor. calibration range. Any DT-500 Series Silicon Diode
Accuracy with Lake Shore calibrated Sensor and DRC- Sensor or PT-100 Series Platinum RTD can be utilized.
Precision ±0.1K or better depending on calibration Requires that an appropriate calibration be purchased
range. Platinum RTD: Conforms
to DIN43760 tolerances for the Sensor. Specify Sensor input position (A or B or
±0.1K. See Lake Shore PT-100 Technical Data for 1-10 on SW-10A)
to assure proper location of calibration
details. Calibrated Sensor and DRC-Precision improves within PROM.
accuracy to±0.01K depending on range. First calibration stored
.
Subsequent Calibrationsstored insamePROM.
Temperature Control: Model DT-500-DRC. Silicon Diode Temperature Sensor
Set-Point: Digital thumbwheel selection directly in (1.5mm diameter X 4.1mm long). Specify response
Kelvin,
(+) Celsius, or (-) Celsius as determined by front- curve .
Panel switch. Remotely settable in Kelvin with BCD Model DT-500CU-DRC-36. Silicon Diode Temperature
or IEEE-488Option. Sensor (8mm diameter
x 3.3mm thick with mounting
Set-Point Resolution: 0.1K or 0.1°C.
Typical Controllability: 0.1K or better in a properly
Model PT-101. Platinum RTD (3.lrnm diameter x 30.5 rnrn
sections. SW-10A) .
hole). Specify response curve .
designed system. long).
Control Mode: Proportional (gain) and integral (reset). Model PT-102. PIatinurn RTD (2.0mmdiameter x 20.3rnrn
Set via front panel or remotely with BCD or IEEE-488 long).
option.
Model PT-103. Platinum RTD (1.8mm diameter x 12.1mm
Heater Output: HI: 0-25 watts (1A max. 25V max). long).
LO: 0-10 watts nominal (1A max or 12V rnax). Isolated
Output. 25-ohm heater is recommended.
Control Sensor: Selected by front-panel pushbutton
independent of Display Sensor within either section.
Specificationssubject to change.
-V-

FIGURE 1.1 Model DRC-84C Digital Cryogenic Thermometer/Controller
-vi-

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-
buttons.
-1-

A 4-digit display clearly and unambiguously shows the temperature
directly in Kelvin or Celsius with 0.1 degree resolution. At low temperatures
(under 30K) a SCALE EXPAND mode increases resolution to 0.01K for monitoring
trends and other relative temperature measurements. Absolute accuracy at
low temperatures is ±0.5K in either mode.
The silicon-diode input section of the DRC-84C is designed to use proven
Lake Shore DT-500 Series DRC-curve silicon-diode Sensors, which provide
measurement accuracy to ±0.5K at low temperatures. Accuracy can be increased
to better than ±0.1K through use of an individually calibrated sensor and
the DRC-Precision option to store the calibration. Any DT-500 Sensor can
be utilized in the latter case.
Lake Shore PT-100 Series 100-ohm Platinum RTD's are the ideal Sensors
for the platinum section. The standard response curve is based on 0.1%
interchangeability at
0 C and a temperature coefficient (0 to 100°C) of
0.00835/°C.
the Lake Shore PT-100 Technical Data sheet. Custom calibrations are avail-
able and can be incorporated into the 84C via the DRC-Precision option.
°
The curve conforms to DIN standard 43760 and is published in
Since silicon-diode sensors can be damaged by exposure to temperatures
above 380K (DT-500DRC Sensors should not be used above 330K to prevent deter-
ioration of their epoxy seals), precautions are recommended in designing
systems for operation at higher temperatures. The preferred approach is to
have diode sensors installed only when the system is operated below room
temperature. Special software limits and error codes are generated if the
instrument is set to control a point above or below the silicon diode or
platinum sensor temperature limits (see Section 3.13
- Table of Error Condi-
tions).
Control temperature is easily selected and read directly in Kelvin
or Celsius on front-panel digital thumbwheel switches and an adjoining scale-
select switch. The switches provide quick and constant display of the set
point with a resolution of 0.1K or C. Temperature controllability is a
function of system design; and performance is often better than
0.1 degree.
°
Both the gain and reset are variable, and can be set from the front
panel to enable the Controller to be precisely tuned to match the system
response over any temperature region. Ample gain and reset have been
designed in to assure fast response, low offset error, and high stability.
Two heater output levels are selectable on the DRC-84C.
Th HI mode
provides up to 25 watts of heater power while the LO mode limits output power
to a nominal 10 watts.
Five options are available with the DRC-80 Series of instruments. One
option
is an analog signal which is proportional to temperature (DRC8-L/A).
This option has a sensitivity of 10 mV/K.
A second option is a ten-position switch (SW-10A)for multiple sensor
readout. This switch is a separate half-rack box which plugs into the Sensor
"B" position of the DRC-84C. The sensor selected is also identified via
digital interface of the DRC-84C, if present.
-2-

Another option is a custom cut PROM (DRC-Precision Option) which
corresponds to the calibration curve of the customer's DT-500 Series sensor.
A combination of a calibration and custom cut PROM will increase display
accuracy to nearly
±.1 Kelvin over the calibrated range. Please note that
any sensor may be used with this option,
i.e., the customer is not re-
stricted to the DRC Series sensors.
There
are two programming options available; each will control the
set-point, the gain and
reset as well as output the displayed temperature
and sensor selected from the
SW-10A.
format while the DRC8-IEEE is in the popular IEEE-488 format.
The
DRC8-BCD-I/O is in a parallel BCD
The DRC-80 Series is designed around a 3870 microprocessor and asso-
ciated support circuits. The
DRC curve is stored in a PROM which can handle
up to 32 break points per curve. The data consists of
a table of temperature
and voltage associated with each break point.
can generate the
DRC curve to an accuracy of better than 0.1 Kelvin over the
entire temperature range
(4.0 - 400K). The DRC diodes match this curve to
±0.5K at Helium and Nitrogen temperatures and to ±1.0K at room temperature.
1.3 Major Assemblies Supplied
These straight line segments
The DRC-84C includes
as standard equipment, in addition to the digital
thermometer-controller, the following:
A. Operating and Servicing Manual
B. Four five Pin Plugs for Temperature Sensor Cables
C. One seven Pin Plug for Monitor of Sensor Output Voltage
and the
DRC8-L/A option
Model DT-500 Series silicon diodes or platinum thermometers
are not
supplied
as part of the DRC-84C instrument.
Complete Specifications, Accessory Equipment and Customs Options
are
listed in the front of the Manual.
1.4 Ordering of Replacement or Additional Sensors
Two different sensor configurations are available for use with the
Model
DRC-80 Series instruments. These are the DT-500-DRC and the DT-500CU-
DRC-36 sensors. Their description
is included elsewhere in this manual. All
sensor configurations are available if the diode is calibrated and a special
PROM
is cut.
More than one curve presently
exists which can be used with the DRC-80
Series instruments.
If additional sensors are ordered for use with your
instrument, you must be certain to order the correct curve
so that your
-3-

instrument will have its stated accuracy. The proper curve may be determined
in one of the following ways:
A. Specify the sensor serial number that is currently being used
with the instrument (serial number is found on the end of the
plastic box in which the sensor was received).
B. Specify the serial number of your instrument. Our records will
indicate with which sensor the instrument is compatible.
C. Remove the top of your instrument and observe the indicator on the
curve PROM.
D. The fourth way is to measure the diode voltage at
4.2K and
give this value to Lake Shore Cryotronics, Inc. when re-
ordering sensors.
Lake Shore PT-100-ohm Platinum RTD’s are available for the platinum
°
section. These thermometers have a 0.1% interchangeability at 0 C and a
temperature coefficient
(0 to 100°C) of 0.00385/°C.
-4-

SECTION II
Installation
2.1 Introduction
This section contains information and instructions necessary for the
installation and shipping of the model DRC-84C Cryogenic Temperature Indicator
and Controller. Included are initial inspection instructions, power and
grounding requirements, installation information and instructions for repack-
aging for shipment.
2.2 Initial Inspection
This instrument was electrically and mechanically inspected prior to
shipment. It should be free from mechanical damages, and in perfect working
order upon receipt. To confirm this, the instrument should be inspected visual-
ly for obvious damage upon receipt and tested electrically by use to detect any
concealed damage. Be sure to inventory all components supplied before dis-
carding any shipping materials. If there is damage to the instrument in tran-
sit, be sure to file appropriate claims with the carrier, and/or insurance
company. Please advise the company
of such filings. In case of parts' short-
ages, please advise the company. The standard Lake Shore Cryotronics warranty
is given on the title page.
2.3 Power Requirements
Before connecting the power cable to line voltage, insure that the instru-
ment is of the proper line voltage and fused accordingly. The line voltage and
fuse are shown on the rear panel of the instrument.
The line voltage can be changed by switching line voltage selector switch
(S2 - Figure 6.5 DRC-84C Component Layout) located on the main printed circuit
board of the unit.
Nominal permissible line voltage fluctuation is
±10% at 50 to 60 Hz.
2.4 Grounding Requirements
To protect operating personnel, the National Electrical Manufacturer's
Association
(NEMA) recommends, and some local codes require, instrument panels
and cabinets to be grounded. This instrument is equipped with a three-
conductor power cable which, when plugged into an appropriate receptacle,
grounds the instrument.
2.5 Installation
The DRC-84C Thermometer/Controller is all solid state and does not
generate significant heat. It may therefore be rack mounted in close proximity
to other equipment in dead air spaces. The heat from such adjacent equipment
should not subject the controller to an ambient temperature in excess of
-5-

50°C (122°F).
to the shock and vibrations which usually accompany high vacuum pumping
systems.
As with any precision instrument, it should not be subjected
The recommended cable diagrams for the sensor diode and heater element
(in the case of the DRC-84C controllers) are shown in Figure 2.1 (a) and
(b).
The use of a four wire diode or resistor connections is highly recommended to
avoid introducing lead IR drops which
will occur if the alternate two lead
sensor cable connection is used. For example, for
a two lead connection with
diodes, every 25 ohms of cable resistance corresponds to a
.1K error above 30
Kelvin.
the diode
in less critical applications where lead resistance can be kept
small. Because of the low resistance of platinum resistance thermometers, the
four lead cable connections must be used to obtain system accuracy. The indi-
cated shielding connections are the recommended standard practice to avoid
ground loops. Figure 2.1
(d) shows the monitor connections for the analog
output of sensor voltage (0-2.5V for diodes,
0-3.0V for platinum, Pin A) and
optional linear analog output of temperature
(0-BV, Pin C). In the case of
the platinum resistor, the buffered output voltage is -20 times the actual
sensor voltage. For example, if the input voltage from the platinum sensor
is 0.0100V, then the buffered output voltage would be -0.2000V.
2.6 Repackaging for Shipment
The alternate wiring scheme shown in Figure 2.1 (c) may be used for
Before returning an instrument to the factory, should repair be neces-
sary, please discuss the malfunction with a factory representative. He may be
able to suggest several field tests which will preclude returning a satisfac-
tory instrument to the factory when the malfunction is elsewhere.
If it is
indicated that the fault is in the instrument after these tests, the represen-
tative will provide shipping and labeling instructions for returning
it.
When returning an instrument, please attach a tag securely to the
instrument itself (not on the shipping carton) clearly stating:
A. Owner and Address
B. Instrument Model and Serial Number
C. Malfunction Symptoms
D. Description of External Connections and Cryostats
If the original carton is available, repack the instrument in a
plastic bag, place in carton using original spacers to protect protruding
controls, and close carton. Seal lid with paper or nylon tape. Affix
mailing labels and "FRAGILE" warnings.
-6-

FIGURE.2.1 Sensor, Cable, and Monitor Connections
-7-

SECTION III
Operating Instructions
3.1 Introduction
This section contains a description
of the operating controls and
their adjustment under normal operating conditions, and typical controller
applications. These instructions are based upon the instrument having been
installed as outlined
in Section II. The diode polarity as shown in Figure
2.1
(a), in particular, must be correct. For the DRC-84C instrument, a 25
ohm heating element is assumed attached to the "Heater" terminals as shown
in Figure
2.1 (b).
3.2 Controls, Indicators, Connectors
The operating controls, indicators and connectors on the DRC-84C
instrument's front and rear panels are shown in Figures 3.1, and 3.2. The
numbers
with leaders to various controls in the figures are keyed to the
entries in Table 3.1.
Table 3.1
- Entry Number Correlation
NO. KEY
1
2
3
4
5
NAME
POWER
NO LABEL
Gain
Reset
NO LABEL
FUNCTION
A.C. line switch (ON/OFF) (Display serves
as indicator light).
Digital set point. Has 0.1 K resolution.
Variable gain allows adjustment of overall
controller gain over
100 to 1 range. Maxi-
mum gain is full clockwise prior to detent
position labeled REM which transfers gain
control to remote BCD or IEEE option when
present. The potentiometer is logarithmic
so that x10 gain is approximately one-half
of full rotation.
Adjusts reset time constant of integrator.
Effectively determines time constant of
integrator between 25 and
1 seconds, minimum
and maximum, respectively. Note that reset
control can be transferred to either the BCD
or IEEE options if one of them is present.
Digital temperature display located behind
filter panel. LED indicators also indicate
scale expand, which sensor is selected for
display, which sensor is selected for con-
trol and type of sensor.
-9-

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6
7
8
9
10
11
12
13
14
15
16
17
Scale Expand
Sensor Display
Sensor Control
Type
Heater Power
HI
Scale
NO LABEL
Fuse
Diode Sensor
Inputs
Platinum Sensor
Inputs
Monitor
With button out, the display reads to
0.1K
at all temperatures; with button in detent
position, temperature reads to
0.01K below
30K, 0.05K between 30K and 100K, and to
0.1K above 100K. Scale expand is indicated
on display panel.
With buttori out, sensor
A temperature is
displayed; with button in detent position,
sensor
B is read and displayed. Sensor
being read
is also indicated on display
panel.
With button out, sensor
A is control
sensor; with button in detent position,
sensor
B is the control sensor. Control
sensor
is also indicated on display panel.
With button out, the silicon diode inputs
are selectable; with button in detent
position, the platinum sensor inputs are
selected
.
With button out, heater power maximum
is 10 watts (LO); in detent position,
full heater power
is available (25
watts).
Hi power LED indicator.
Selects either the Celsius or Kelvin
scale for both the display and the
set-point.
A.C. line cord.
A.C. line fuse.
Diode
Sensor A and B input lead terminals
(Pin
A, I+, Pin E, V+, Pin B, I-, Pin D,
V-, Pin H, Shield).
Same connections
as for diode sensors.
Analog output of sensor voltage (0-2.5V,
pin
A) and optional linear analog output
of temperature (0-4V, pin C). Pin B
is ground for sensor voltage, Pin D is
ground for linear analog output.
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FIGURE 3.1 DRC-84C Front Panel
FIGURE
3.2 DRC-84C Back Panel
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18
19
20
21
Heater
Fuse
Interface
GND
Heater element terminals (25 ohm heater
required for
25 watts of power).
Output power fuse
(1.0 ASB specified).
BCD input of set point, gain and reset
output of temperature. Also IEEE
interface port.
Instrument or case ground
3.3 Temperature Readout
The sensor(s) and heater should be installed following the
suggestions listed
in the "Installation and Application Notes for
Cryogenic Sensors" brochure in Section VIII.
Connect the sensor(s) to the instrument following the diagram in
Figure 2.1.
Depress the power switch and observe that the display shows the
proper temperature relative to the sample temperature.
If the diode or lead wires are shorted or if the diode is connected
backwards, the display
will read (----) and flash 428.0. In the case of
an open current or voltage lead, the display
will slowly drift higher in
temperature from the last voltage reading taken by the A/D converter.
The sensor and readout display for diodes should follow Table 3.4
which illustrates typical values expected of the standard DT-500-DRC or
DT-500CU-DRC-36sensors for your appropriate curve.
The DIN standard curve for the platinum sensors is given in Table 3.7.
If the instrument or sensor does not agree with values listed in the
table, within the accuracy of the system, consult sections on installation
and/or section on troubleshooting to determine the cause and cure of the
malfunction. If an error code is displayed, refer to Section 3.13 for
possible corrections.
3.4 Analog Control
The digital set point of temperature is converted to an analog set
point of voltage which is then compared to the sensor voltage by summing
two respective currents of opposite sign.
To familiarize yourself with the DRC-84C control section,set the
instrument
so that you are reading and controlling with the same sensor.
Turn the reset (integral) control section off. Establish a set point
temperature several degrees above the display temperature. Gradually
turn the gain clockwise from a minimum position. Note that as the gain
is increased, the offset between the display temperature and the set point
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will be decreased. The gain potentiometer is logarithmic with rotation and
covers a
100 to 1 range so that the gain at mid-rotation is ten times the
minimum gain.
With most systems, an oscillation in temperature
will occur at some
clockwise rotation. Further clockwise rotation
will cause a wild oscilla-
tion in temperature. The gain should then be backed off until a stable
control temperature occurs. Note that an offset between display tempera-
ture and set point will still be present.
Finally, turn on the reset control. With the addition of reset, the
temperature error between setpoint and control temperature should reduce to
zero. The rate at which this reduces to zero is determined again by a
clockwise rotation with the shortest time constant occurring at full clock-
wise rotation.
Note that the system can become unstable again with too much reset
added.
temperature control.
Slight variations in the gain and/or reset should give stable
The
HI-LO power switch also changes the loop gain with the HI posi-
tion increasing the gain by a factor of approximately two.
It may be
necessary when changing from
LO to HI power setting to reduce the gain
slightly to compensate for the increased overall loop gain.
3.5 Analog Output of Temperature
The analog output of temperature takes the display temperature and
converts
it to an analog signal which has a sensitivity of 10 mV/K under
normal operation. The analog output voltage is located on the monitor
connector (Key
17 of Figure 3.2). See Section 3.10 for installation notes
on DRC-8-L/A.
3.6 Standard DT-500-DRC and DT-500CU-DRC-36 Curves
The standard DT-500-DRC and DT-500CU-DRC-36 curve is explained in
Section 3.3. The Tables include a list of PROM sensor voltages and break-
points used in the linearization
of the DRC curve to arrive at the correct
temperature readout.
3.7 The 10-Sensor Selector Switch
The 10-Sensor Selector Switch includes an umbilical which ties to the
DRC-84C main printed circuit board (via a 16-pin ribbon cable header which
plugs into internal socket JC (see Figure 6.5, DRC-84C Component Layout)
and a cable to connect the selected sensor leads to the DRC-84C (Sensor
Plug
B is either Key 15 or Key 16 of Figure 3.2).
The SW-10A is supplied with an 18" cable which is shielded and has
male 5-pin amphenol connectors at each end. This cable connects between
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J11 of the SW-10A and one of the B sensor plugs of the DRC-84C. Sensors
are connected to the SW-10A via printed circuit edge J10.
A 36-pin edge
card connector and hood has been supplied with the SW-10A. Connectors to
this edge J10 are given in Table 3.5.
3.8 Remote Parallel BCD Input/Output Option
The BCD option consists of a
16 bit parallel output of temperature
along with a scale expand
bit to indicate decimal point, a 15 bit parallel
input of set point in Kelvin degrees or Celsius (depending on switch posi-
tion), a
4 bit parallel input of gain setting, a 4 bit parallel input of
reset setting, and a
4 bit output of switch position from the SW-10A.
Table 3.6 can be used for input and output line coding.
The BCD in and out is handled through connector
J4
(denoted on back
panel as INTERFACE), a
50 pin connector on the rear panel of the instrument.
Two internal jumper wires are placed on the printed circuit board
in front
of internal connector JE. Cutting these jumpers allows the user to enable
the remote set point by setting Pin 38,
J4 high (see Table 3.6). If the
option was installed prior to shipment, these jumpers have already been cut.
Options that are field installed need to have their jumpers cut by the user.
Data latches internal to the instrument provide a 1-2-4-8 code using
positive logic with standard TTL levels of
0.4 volts or less for low (logic
0) and 2.4 volts or higher for the high (or 1) state under full load con-
ditions. The drivers are sufficient to drive two standard loads, 3.2mA,
in the low state.
Set point is input to the instrument via a remote set point enable
pin (externally generated,
pin 38). With no connection made to the external
enable pin, the option selects the internal (front panel) set point. When
the unit is receiving a set point externally, the front panel set
point switches are disabled.
The sensor temperature output
is externally gated through the use of
an internally generated data valid pulse.
Input of gain value and reset can be seen
in the following tables
(highs are denoted as "1" and lows are denoted as "0").
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