SRS Labs CTC100 User manual


Version 1.9 (January 27, 2017)
User Manual
CTC100
Cryogenic Temperature Controller
Distribution in the UK & Ireland
Lambda Photometrics Limited
Lambda House Batford Mill
Harpenden Herts AL5 5BZ
United Kingdom
E: [email protected]
W: www.lambdaphoto.co.uk
T: [phone]
F: [phone]
Characterisation,
Measurement &
Analysis


CTC100 Programmable Temperature Controller
Certification
Stanford Research Systems certifies that this product met its published specifications at the time of shipment.
Warranty
This Stanford Research Systems product is warranted against defects in materials and workmanship for a period of
one (1) year from the date of shipment.
Service
For warranty service or repair, this product must be returned to a Stanford Research Systems authorized service
facility. Contact Stanford Research Systems or an authorized representative before returning this product for repair.
Information in this document is subject to change without notice.
Copyright © Stanford Research Systems, Inc., 2017. All rights reserved.
Stanford Research Systems, Inc.
1290-C Reamwood Avenue
Sunnyvale, California 94089
Phone: [phone]
Fax: [phone]
www.thinkSRS.com
Printed in the USA

Contents i
CTC100 Programmable Temperature Controller
Contents
Safety and preparation for use................................................................................v
Specifications ...........................................................................................................vii
Introduction 1
Connecting the inputs and outputs ........................................................................3
Temperature sensor inputs ..................................................................................................... 3
100W heater outputs .............................................................................................................. 8
±10V analog I/O channels....................................................................................................... 9
Relays, digital I/O, and virtual channels ................................................................................ 10
Operation 13
Quick start tutorial .................................................................................................14
Turn the instrument on.......................................................................................................... 14
The Select screen ................................................................................................................... 14
Configure the sensor inputs................................................................................................... 14
If the sensor reading does not appear................................................................................... 15
Plot data.................................................................................................................................. 15
Test the outputs ..................................................................................................................... 16
Set the data logging rate......................................................................................................... 16
Save data to and retrieve data from a USB memory device ................................................ 17
Interface with a computer...................................................................................................... 17
Control a temperature........................................................................................................... 19
Acquiring and logging data ....................................................................................23
Input filters.............................................................................................................................. 24
Custom calibration tables ...................................................................................................... 24
Virtual channels ...................................................................................................................... 26
Logging data to USB ............................................................................................................... 27
ADC sampling and logged data ............................................................................................. 27
Format of CTC100 log files ................................................................................................... 28
The system fan ........................................................................................................30
Rack mounting the CTC100 ..................................................................................30
Using PID feedback.................................................................................................31
How stable is the CTC100’s feedback control? ................................................................... 31
Basic concepts ........................................................................................................................ 31
Manual tuning.......................................................................................................................... 32
Automatic tuning algorithms.................................................................................................. 35
Using the automatic tuner...................................................................................................... 38
Using alarms with PID feedback loops.................................................................................. 40
Front-panel controls ...............................................................................................41
USB logging indicator ............................................................................................................. 41
“Help” key .............................................................................................................................. 41
“Output Enable” key .............................................................................................................. 41
“Select Channels” screen ....................................................................................................... 42
“Show Data” screen............................................................................................................... 42

Contents ii
CTC100 Programmable Temperature Controller
“Program” screen................................................................................................................... 48
“Setup” screen........................................................................................................................ 52
Firmware updates ...................................................................................................73
Replacing the memory backup battery ...............................................................74
Removing an I/O or CPU card ..............................................................................75
Remote programming 77
Connecting to the CTC100................................................................................................... 77
Communication, assembly, and run-time errors .................................................................. 80
Concurrent macros................................................................................................................ 80
Macro names .......................................................................................................................... 81
Command syntax ................................................................................................................... 81
Remote instructions ...............................................................................................87
Miscellaneous instructions ..................................................................................................... 87
IEEE 488.2 Instructions........................................................................................................... 89
Program menu........................................................................................................................ 93
System setup........................................................................................................................... 96
Channel setup......................................................................................................................... 99
Error codes........................................................................................................................... 109
Startup macros ..................................................................................................................... 110
Sample macros ......................................................................................................111
Temperature profiles ........................................................................................................... 111
Control a feedback setpoint with an analog input.............................................................. 112
Show channels with tripped alarms on the Numeric screen ............................................. 112
Show the PID setpoint in a virtual channel ......................................................................... 113
Linearizing outputs when interfacing with external power supplies .................................. 113
Control instrument functions with the digital IO lines ....................................................... 113
Drive a solid state relay with the digital IO lines................................................................. 114
PC applications 119
PTCFileConverter ................................................................................................120
FileGrapher ............................................................................................................122
File menu............................................................................................................................... 122
Edit menu.............................................................................................................................. 122
Process menu ....................................................................................................................... 124
Special menu......................................................................................................................... 126
Command line and macro instructions ............................................................................... 127
Circuit description 131
CPU board............................................................................................................................ 131
Backplane.............................................................................................................................. 132
Front panel............................................................................................................................ 134
GPIB card.............................................................................................................................. 134
Sensor input cards................................................................................................................ 134
Heater driver cards .............................................................................................................. 135
Analog I/O card ................................................................................................................... 136
Digital I/O card .................................................................................................................... 137

Contents iii
CTC100 Programmable Temperature Controller
Parts List 139
Chassis (assembly 199) ........................................................................................................ 139
CPU card (assembly 207) .................................................................................................... 140
Backplane (assembly 209).................................................................................................... 143
Front panel (assembly 210) ................................................................................................. 146
GPIB option (assembly 289)................................................................................................ 147
2-channel thermistor/RTD/diode reader (assembly 310)................................................ 148
100W DC output card (assembly 206) .............................................................................. 152
Analog I/O card (assembly 297)......................................................................................... 155
Digital I/O card (assembly 298).......................................................................................... 157
Schematics 161

Safety and Preparation for Use v
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CTC100 Programmable Temperature Controller
Safety and preparation for use
Line voltage
The CTC100 operates from an 88 to 264 VAC power source having a line frequency between 47
and 63 Hz.
Power entry module
A power entry module, labeled AC POWER on the back panel of the CTC100, provides
connection to the power source and to a protective ground.
Power cord
The CTC100 package includes a detachable, three-wire power cord for connection to the power
source and protective ground.
The exposed metal parts of the box are connected to the power ground to protect against
electrical shock. Always use an outlet which has a properly connected protective ground. Consult
with an electrician if necessary.
Grounding
A chassis grounding lug is available on the back panel of the CTC100. Connect a heavy duty
ground wire, #12AWG or larger, from the chassis ground lug directly to a facility earth ground to
provide additional protection against electrical shock.
Line fuse
Use a 10 A/250 V 3AB Slo-Blo fuse.
Operate only with covers in place
To avoid personal injury, do not remove the product covers or panels. Do not operate the
product without all covers and panels in place.
Serviceable parts
The CTC100 does not include any user serviceable parts inside. Refer service to a qualified
technician.

Specifications vii
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CTC100 Programmable Temperature Controller
Specifications
CTC100 temperature controller
Minimum sampling rate 1 Hz
Maximum sampling rate 50 or 60 Hz, depending on AC line frequency
Data logging rate 10 samples/second/channel – 1 sample/hour/channel (can be set
independently for each channel or globally for all channels)
Display resolution 0.001 °C, °F, K, V, A, W, etc. if –1000 < displayed value < 1000;
6 significant figures otherwise
PID feedback auto-tuning Single step response or relay tuning with conservative, moderate, and
aggressive response targets
Display 320 × 240 pixel color touchscreen; numeric and graphical data displays.
Alarms Upper and lower temperaturelimits or rate-of-change limits can be set on each
channel.If exceeded, an audio alarm and a relay closure occur.
Computer interface USB, Ethernet, and RS-232; optional GPIB (IEEE488.2)
Power 10 A, 88 to 132 VAC or 176 to 264 VAC, 47 to 63 Hz or DC
Dimensions 8.5"× 5" × 16" (WHL)
Weight 13 lbs.
Warranty One years parts and labor on defects in material and workmanship.
Thermistor, diode, and RTD inputs
Inputs Four inputs for 2-wire or 4-wire thermistor, diode, or RTD
Connectors Two 9-pin D-sub sockets
RTDs and thermistors
Range 0 – 10, 30, 100, 300Ω; 1, 3, 10, 30, 100, 300 kΩ; 2.5 MΩ, or auto
Excitation current Low power High power
10 Ω range 1 mA 3 mA
30 Ω range 300 µA 3 mA
100 Ω range 100 µA 2 mA
300 Ω range 30 µA 1 mA
1 kΩ range 10 µA 500 µA
3 kΩ range 3 µA 200 µA
10 kΩ range 1 µA 50 µA
30 kΩ range 300 nA 50 µA
100 kΩ range 100 nA 5 µA
300 kΩ range 30 nA 5 µA
2.5 MΩ range 1 µA 1 µA
Initial accuracy (AC current, at midrange)
10 Ω range ±0.007 Ω ±0.005 Ω
30 Ω range ±0.03 Ω ±0.005 Ω
100 Ω range ±0.07 Ω ±0.008 Ω
300 Ω range ±0.25 Ω ±0.015 Ω (=±50 mK for Pt100 RTD at 25°C)
1 kΩ range ±0.6 Ω ±0.05 Ω
3 kΩ range ±2 Ω ±0.1 Ω
10 kΩ range ±6 Ω ±0.25 Ω
30 kΩ range ±25 Ω ±1 Ω
100 kΩ range ±150 Ω ±4 Ω
300 kΩ range ±1 kΩ ±13 Ω
2.5 MΩ range ±3 kΩ ±3 kΩ
Typical drift due to temperature (at midrange)
10 Ω range ±0.0002 Ω/°C ±0.0001 Ω/°C

Specifications viii
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CTC100 Programmable Temperature Controller
30 Ω range ±0.0004 Ω/°C ±0.0001 Ω/°C
100 Ω range ±0.002 Ω/°C ±0.0002 Ω/°C
300 Ω range ±0.004 Ω/°C ±0.0004 Ω/°C
1 kΩ range ±0.01 Ω/°C ±0.001 Ω/°C
3 kΩ range ±0.06 Ω/°C ±0.003 Ω/°C
10 kΩ range ±0.2 Ω/°C ±0.01 Ω/°C
30 kΩ range ±1 Ω/°C ±0.02 Ω/°C
100 kΩ range ±3 Ω/°C ±1 Ω/°C
300 kΩ range ±20 Ω/°C ±2 Ω/°C
2.5 MΩ range ±30 Ω/°C ±50 Ω/°C
RMS noise (DC current, at midrange)
10 Ω range 0.0003 Ω 0.0001 Ω
30 Ω range 0.001 Ω 0.0001 Ω
100 Ω range 0.002 Ω 0.0002 Ω
300 Ω range 0.006 Ω 0.0003 Ω ( = 1.4 mK for Pt100 RTD at 25°C)
1 kΩ range 0.02 Ω 0.0007 Ω
3 kΩ range 0.06 Ω 0.002 Ω
10 kΩ range 0.2 Ω 0.007 Ω
30 kΩ range 1.0 Ω 0.008 Ω
100 kΩ range 6 Ω 0.12 Ω
300 kΩ range 40 Ω 0.2 Ω
2.5 MΩ range 10 Ω 10 Ω
Diodes
Excitation current 10 µA
Initial accuracy ± 100 ppm
Drift ±5 ppm/°C
Voltage input 0 – 2.5 V
Initial accuracy 10 µV + 0.01% of reading
Drift ±5 ppm/°C
RMS noise 3 µV
100W DC outputs
Output Two unipolar DC current sources
Connector #6 screw terminals. Accepts 12–22 AWG wire or #6 spade terminals up to
0.31” wide. Max torque 9 in-lb.
Range 50 V 2A, 50V 0.6A, 50V 0.2A, 20V 2A, 20V 0.6A, 20V 0.2A
Output resolution 16 bit
Accuracy ±1 mA (2 A range)
±0.5 mA (0.6 A range)
±0.2 mA (0.2 A range)
Noise (rms), 25 Ω load, 5 µA (2 A range)
DC–10 Hz 1.5 µA (0.6 A range)
0.5 µA (0.2 A range)
Analog I/O
Inputs/outputs 4 voltage I/O channels, independantly configurable as inputs or outputs
Connector 4 BNC jacks
Range ±10 V
Resolution 24-bit input, 16-bit output
ADC noise 30 µV RMS = 100 µV p-p (at 10 samples/s)

Specifications ix
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CTC100 Programmable Temperature Controller
Digital I/O
Digital I/O
Inputs/outputs 8 optoisolated TTL lines, configurable as either 8 inputs or 8 outputs
Connector One 25-pin D-sub socket
Relays
Outputs 4 independent SPDT relays
Connector One 12-pin 3.5mm header
Maximum current 5 A
Maximum voltage 250 VAC

I
Introduction 1

CTC100 Programmable Temperature Controller
Introduction
The CTC100 is a high-performance cryogenic temperature controller that can monitor and
control temperatures with millikelvin resolution. Its features include:
4 temperature sensor inputs
Each of the CTC100’s four temperature inputs can read RTDs, thermistors, and diodes.
Each temperature input channel has its own 24-bit ADC with ten input ranges that can be
automatically or manually selected. By default each sensor is read 10 times per second, but the rate
can be set as low as 1 Hz or as high as the line frequency (50 or 60 Hz).
Each input has an independent excitation current source. The excitation current is automatically
selected based on the input range. The direction in which the excitation current flows through the
sensor can be reversed to detect EMF errors, and the CTC100 can automatically reverse the
current direction at every ADC reading and display the average of forward and reverse current
readings.
Standard calibration curves for a variety of sensors are included, and custom calibration curves of
up to 200 points each can be entered by saving a text file on a USB memory stick and then plugging
the memory stick into the CTC100. Calibrations can be adjusted by entering an offset and gain
from the front panel.
Each sensor input has high and low level or rate-of-change alarms. Alarms can be latching or non-
latching and when triggered, can shut off a heater output, trip a relay, and/or create one of four
alarm sounds.
Sensor inputs can be lowpass-filtered to reduce noise and/or differenced with another channel.
The rate of change of sensor inputs can be calculated.
In addition, any of the CTC100’s four voltage I/O channels can be used to read pre-amplified
sensor signals.
2 powered and 4 unpowered heater outputs
The CTC100 has two heater outputs, each capable of delivering up to 100W of power to a 25
ohm heater. In addition, four unpowered voltage I/O channels can be used to drive heaters with
the help of an external amplifier.
Up to 6 feedback control loops
Each of the heater outputs can be controlled by a PID feedback loop. A feedback loop continually
adjusts the heater power in order to keep a sensor at a constant temperature. Any of the CTC100’s
channels can be selected as the input for each feedback loop. Feedback time constants can be
adjusted between about 200 ms and 10 hours. .
PID feedback parameters can be tuned manually or automatically. Depending on the amount of
overshoot that is acceptable, aggressive, moderate, or conservative tuning goals can be selected.
Up to ten sets of PID parameters can be stored for each channel; each set of parameters can be
assigned a temperature range and automatically recalled when the temperature falls within that
range. The temperature sensor used for the feedback loop can also be selected based on the
temperature.
Setpoints can be ramped at a fixed rate or, with a user program, set from an analog input.
Feedforward and cascade feedback are supported.

I
Introduction
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2
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CTC100 Programmable Temperature Controller
General-purpose analog I/O, digital I/O, relays, and virtual channels
The CTC100 has four general-purpose ±10V voltage I/O channels read by a 24-bit ADC.
Custom calibration curves and/or offset/gain controls can be used to convert voltage readings to
pressure, temperature, etc.
The CTC100 also has eight digital I/O channels that can interact with user programs. Four 5A
relays can be used for process control. Three virtual channels not connect to any physical input
allow calculated values (such as the difference between two channels, or a value calculated by a user
program) to be displayed, graphed, and logged.
Graphical touchscreen display
The CTC100’s color LCD display can show any combination of temperature measurements and
heater outputs on graphs or numeric displays. Up to eight channels can be plotted, either on a
single graph with a common Y axis or on separate graphs with independent Y axes.
Touchscreen operation makes the instrument versatile and easy to use.
Data logging to USB memory devices
Up to 4096 readings per channel can be logged to the CTC100’s internal memory. For longer-
term storage, data can be logged to standard USB memory sticks or hard drives. Readings can be
logged at intervals as short as 0.1 s or as long as 1 hour. The log rate can be set independently for
each channel, or a single global rate used.
Data logged to USB devices can be transferred to a computer by plugging the USB device into a
PC and copying the log files. Windows applications are included to graph CTC100 log files and to
convert them to various ASCII text formats.
Computer communications
Each of the CTC100’s front-panel controls has a corresponding text command that can be sent
over USB, Ethernet, and either RS-232 or an optional GPIB interface. When the USB interface is
used, the CTC100 appears on the computer as a standard COM port and can be controlled by any
software that is compatible with an RS-232 port.
Eight digital I/O lines are also provided; these can interact with user programs to control most
aspects of the instrument’s operation.
User programs
User programs (macros) consisting of one or more remote commands can be uploaded to the
CTC100, either by sending them through one of the communications ports or by saving them as
text files on a USB memory device and then plugging the device into the CTC100. Macros can be
started or stopped, and their progress monitored, from the front panel. Macros can call other
macros, and conditional statements and loops are supported. Using the CTC100’s virtual channels,
values calculated by macros can be plotted on-screen, saved to logs, and/or used as inputs for
feedback loops. Up to 10 macros can run concurrently.
At a basic level, macros can be used to program temperature profiles or other sequences of
events. Macros can also be employed in more advanced ways to tailor the behavior of the CTC100
for your experiment; for example, infinite-loop macros running as background tasks can take steps
to address alarm conditions or automatically switch between sensor inputs (or heater outputs)
depending the value of some input.

I
Introduction
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3

CTC100 Programmable Temperature Controller
Connecting the inputs and outputs
The CTC100 has four temperature sensor inputs, two powered heater outputs, four ±10V
analog I/O channels, four 5A relays, and eight digital I/O lines.
Temperature sensor inputs
The CTC100 has four multi-range inputs, each of which can read resistive sensors having
resistances between 1 Ω and 2.5 MΩ, and diode sensors having voltage drops of up to 2.5V.
Standard calibration curves are included for the sensors shown in the following table. The
“Range” column indicates the range of the standard calibration curve; if the sensor is outside this
range, no reading appears. It may be possible to increase the range by uploading a custom
calibration curve.
Sensor
class Manufacturer Calibration type
Range,
K
Diode
Scientific Instruments
Si410 1.0–450
Si430 1.0–400
Si440 1.0–500
LakeShore; Omega DT-470 (=CY7) 1.4–475
DT-670 (=CY670) 1.4–500
Cryo-Con
S700 1.5–475
S800 1.4–385
S900 1.5–500
Ruthenium
oxide
LakeShore
RX-102A 0.050–40
RX-103A 1.2–40
RX-202A 0.050–40
Scientific Instruments RO600 1.0–300
Cryo-Con R400 2.0–273
R500 0.050–20
RTD All IEC751 (DIN43760) 48.15–1173.15
US 48.15–1173.15
Thermistor
Measurement
Specialties,
Inc.
(formerly YSI);
Omega
100 Ω193.15–373.15
300 Ω193.15–373.15
1000 Ω193.15–373.15
2252 Ω193.15–523.15
3000 Ω193.15–523.15
5000 Ω193.15–523.15
6000 Ω193.15–523.15
10000 Ωtype B (32.66 k:at 0°C) 193.15–523.15
10000 Ωtype H (29.49 k:at 0°C) 193.15–523.15
30 kΩ233.15–523.15
100 kΩ233.15–423.15
300 kΩ298.15–423.15
1 MΩ298.15–423.15
Other kinds of resistive and diode sensors can be used, but require custom calibration curves.
For example, rhodium-iron, germanium, and carbon-glass sensors have too much sensor-to-sensor
variability to use a standard curve, and therefore must be individually calibrated.

I
Introduction
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4

CTC100 Programmable Temperature Controller
Connecting the sensor
The CTC100 has two 9-pin D-sub (DB9) sockets that mate with any standard DB9 plug, such as
Amphenol L717SDE09P with backshell 17E-1657-09. Two plugs and backshells are provided with
each CTC100. Here is the pinout of the two sockets, as they appear when looking at the CTC100’s
back panel:

Sensors In 1 and In 2, for example, should be connected as shown below.
The +I and –I pins provide an excitation current that should be routed to the temperature sensor
through two wires, preferably a shielded twisted pair. The excitation current produces a voltage
across the sensor that is measured with pins +V and –V. These pins should be connected to the
sensor with two additional wires (preferably a second shielded twisted pair): +V should be
connected to +I as close as possible to the temperature sensor, and likewise –I should be connected
to –V as close as possible to the sensor. Because essentially no current flows through the V leads,
they accurately transmit the sensor voltage to the CTC100.Using four wires instead of two ensures
that the CTC100 measures the resistance of the sensor and not the wires going to the sensor.
The +V and –V pins are internally connected to the +I and –I pins with 1 MΩ resistors, so the
sensor will still work if the +V and –V pins are not connected. However, the reading is more
accurate when all four pins are connected.
Resistive sensors: Four-wire RTDs usually have two wires of one color attached to one side of
the RTD, and two of a second color attached to the other side. In this case, the RTD should be
wired to the CTC100 in one of the following two ways (assuming the leads are white and black):
–
V
–
I Ground +V +I
Option 1 White White Unconnected Black Black
Option 2 Black Black Unconnected White White
Two-wire sensors can be converted to four-wire sensors by soldering two additional wires to the
existing leads, one on each side of the sensing element and as close to the sensing element as
possible. A good-quality solder joint is essential; the wires should not be connected to the sensor by
pressure alone (e.g. crimping or clamping), as any resistance within the joint becomes part of the
measured sensor resistance.
The higher the resistance of an RTD or thermistor, the more sensitive it is to ambient
electromagnetic noise and the greater the need for a shielded cable.
5
9
8
7
6
–I2
–V2
+V2 +I2
Gnd
4
3
2
1
–I1
–V1
+V1 +I1
5
9
8
7
6
–I4
–V4
+V4 +I4
Gnd
4
3
2
1
–I3
–V3
+V3 +I3

I
Introduction

5

CTC100 Programmable Temperature Controller
Diode sensors: Diode sensors can be connected in either direction. If the cathode is connected
to –V and –I and the anode to +V and +I, &KDQQHO&XUUHQW should be set to Forward. If the
diode is connected in the opposite direction, the current should be set to Reverse.
Diode sensors are especially susceptible to electromagnetic noise because the diode rectifies any
noise picked up by the sensor leads, increasing the measured voltage. It may be necessary to put
EMI filters not only the on the sensor leads but also on all other leads entering the Dewar. The
filters should be located at the point where the wires enter the Dewar, and the Dewar itself should
be grounded. D-sub and circular connectors with built-in filters can be obtained from Spectrum
Advanced Specialty Products. We have found their 4000 pF pi filters to be effective. These filters
include capacitors to ground, which should be connected to the Dewar.
AD590 sensors: The CTC100 can read AD590 sensors if the sensor is connected in series with a
2 k resistor as shown below. Note that the diagram shows the sensor connected to channel A, but
it can also be connected to channel B. The diagram shows the back of the DB9 connector, that is,
the side that you solder to.

The 2 k resistor must have a low temperature coefficient of resistance (TCR). Ordinary resistors
have a TCR of about 100 ppm/°C, which means that the sensor reading will increase by about 30
mK for each 1°C rise in the ambient temperature. Thermal drift can be reduced substantially by
using a 5 ppm/°C resistor available from SRS; ask for part number 4-02502-457. For even better
stability, a 1 ppm/°C resistor such as the Riedon USR2G-2KX1, available from Digi-Key, can be
used. In any case, to minimize noise and drift, the resistor should be soldered directly to the pins on
the DB9 plug and covered up with the backshell.
Because AD590 sensors are highly sensitive to electromagnetic interference, the AD590 wires
and package must be shielded, with the shield connected to pin 3 of the DB9 connector.
Excitation current
The CTC100 measures the resistance of the sensor by passing an excitation current through it.
The larger the excitation, the less noise the temperature reading will have. However, if the
excitation is too large it will heat the sensor and cause higher than expected readings. Therefore,
each channel can be configured for either “low power” or “high power” operation:
• Low power: minimizes sensor heating. This option is mainly for use with thermistors in
cryogenic applications. To compensate for the fact that heat conductivity decreases (and
thermistor resistance increases) as the temperature approaches absolute zero, the amount of
power that the sensor dissipates decreases as the measurement range is increased.
• High power: minimizes noise. Power dissipation is kept roughly constant as the
measurement range is increased. This option is for use with RTDs or with any kind of sensor
at non-cryogenic temperatures.
• Auto power: uses low power if the sensor type is set to thermistor or ROX, or high power
if the sensor type is set to RTD.
The CTC100 has 12 measurement ranges. Within any given range, it generates a constant
excitation current as shown in the table below. Note that the range has to be greater than the
sensor resistance, so if the sensor resistance is 10 k, for example, the range should be 30 k.
For diode sensors the range is always 2.5V and the excitation current is always 10 µA.
AD590
+I
1
6
5
9
+V
–V –I +

I
Introduction

6

CTC100 Programmable Temperature Controller
The graph below shows how the amount of power dissipated by the sensor depends on the range
and power settings. Sensor heating (degrees above the ambient temperature) is proportional to
power dissipation.
Left: the amount of current passed through the sensor by the CTC100;
right: the amount of power that the sensor dissipates due to that current
The table below shows some representative noise, electronic accuracy, and self-heating values for
free-standing sensors at room temperature. Note that the amount of self-heating can vary
dramatically depending on the thermal conductivity of whatever the sensor is attached to or
immersed in.
Noise Accuracy Self-heating
Low
power
High
power
Low
power
High
power
Low
power
High
power
100Ω RTD 20 mK 0.8 mK 640 mK 40 mK 0.09 mK 100 mK
1 kΩ thermistor 2 mK 0.08 mK 60 mK 3 mK 0.009 mK 40 mK
10 kΩ thermistor 2 mK 0.02 mK 50 mK 2 mK 0.0009 mK 25 mK
100 kΩ thermistor 9 mK 0.04 mK 220 mK 3 mK 0.00009 mK 2.5 mK
Noise, accuracy, and amount of self-heating at 25°C for several sensors. “Accuracy” is the electronic
accuracy of the CTC100 immediately after calibration and does not account for self-heating or the
accuracy of the sensor. “Self-heating” is the rise above ambient temperature of a ~1 mm diameter sensor
hanging by its leads in still air (dissipation constant 1 mW/°C).
The graphs below show how electronic noise varies with temperature for several types of
sensors.

I
Introduction

7

CTC100 Programmable Temperature Controller

RMS noise levels for 100

and 1000

platinum RTD sensors as a function of temperature. At low power, the 100

and 1000

sensors mostly have the same noise level.

RMS noise levels for 100

, 10k

, and 1M

(at 25  C) thermistors as a function of temperature

I
Introduction

8

CTC100 Programmable Temperature Controller

RMS noise for DT-670 diode sensor as a function of temperature.
The direction of the excitation current can be set by the user to forward, reverse, or AC
(switching between forward and reverse with each sample). AC current is recommended for
resistive sensors to reduce noise and drift. AC current cannot be used with diode sensors. See the
discussion of the Current setting on page 60.
100W heater outputs
The CTC100 has two outputs for resistive heaters. The output connectors are #6-32 wire clamp
screws and will accept bare wire between 12 and 22 AWG. For the most reliable connection it is
recommended to crimp a #6 insulated spade terminal (such as TE Connectivity 34080 for 16–22
AWG wires or 35559 for 14–16 AWG wires) to the end of each heater wire. A crimp tool such as
TE Connectivity 58433-3 should be used for this purpose.
The CTC100 should always be switched off and unplugged when connecting the heater outputs.
Each output has two voltage ranges (50 V and 20 V) and three current ranges (2A, 0.6A, and
0.2A). Each output also has an auto-range setting that continuously adjusts the current and voltage
ranges to the smallest values needed to reach the channel’s Hi Lmt setting.
The 0.6A and 0.2A current ranges offer lower noise levels than the 2A range and are intended to
be used when more precise control is needed. On the other hand, the 20V range is only included
for safety reasons and it has essentially the same performance as the 50V range.
The maximum power that each output can deliver depends on the resistance of the heater as
shown below.