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10.4.6 Thermocouple Temperature Curves
Refer to Appendix A for lists of data points in each curve and Table 1-2 for thermocouple sensor performance.
10.4.7 Specifications
The 3464 Option Card input specifications are listed in Table 1-2.
10.5 MODEL 3465 SINGLE CAPACITANCE INPUT OPTION CARD
This option adds a capacitance input to the Model 340 Temperature Controller. The new input appears on the
display as C. It controls temperature in strong magnetic fields using Lake Shore Model CS-401 or CS-501
capacitance temperature sensors. The standard inputs remain in the instrument and are fully functional.
The Model 340 does not support temperature conversion for the capacitance input. The temperature
response of capacitance sensors shifts with thermal cycling, making calibration unpredictable. All 3465 option
measurement and control must be done in sensor units.
With this option, we recommend operating the Model 340 with two sensors installed at the control point. Use a
diode or resistive sensor in one of the standard inputs to establish a control temperature and stabilize the
system in a low magnetic field. Then shift control to the capacitance sensor before increasing field strength.
10.5.1 OPTION INSTALLATION
To install the 3465 Option into a Model 340 follow the installation procedure in Paragraph 10.3.1. Only one
option board can be installed in the Model 340 at a time. To verify which option if any is installed in a Model
340, press Options, then press More three times. Option identification displays on the REVISION
INFORMATION screen. If options change, the Model 340 changes all parameter settings to default.
10.5.2 SENSOR INSTALLATION
10.5.2.1 Sensor Input Connector
A six-pin connector on the 3465 attaches the four sensor leads and shields.
Capacitance temperature sensors are commonly two-lead devices, but four-lead
measurement is recommended. Make the change from four-lead to two-lead as close
to the sensor as practical.
Capacitance temperature sensors are not polarized; use either lead as the positive or
negative lead. However, 3465 option measurement is polarity dependent; be sure to
attach the V+ and I+ to one sensor lead and the V– and I– to the other.
10.5.2.2 Measurement Point Connection
Refer to Paragraph 2.3 for general installation guidelines for any cryogenic sensor.
When using a capacitance sensor the AC excitation must also be considered.
It is often necessary to place the capacitance sensor very near a second control sensor. The 4.88 kHz
excitation of the 3465 option can interfere with the sensitive DC measurements of the standard inputs. Tightly
twist the lead wires of each sensor and separate them from the leads from the other sensor. Test any system
for sensor interference before it is permanently sealed.
10.5.2.3 Grounding and Shielding
For lowest measurement noise, do not ground any sensor leads. The instrument usually operates with more
noise if one of the leads is grounded. Grounding more than one lead is not recommended.
Shielded cable is recommended because of the AC excitation of the sensor. Shielding reduces excitation
noise transmitted into the measurement system. Shielding outside the cryostat is recommended, but it is
difficult to use shields inside. Connect a cable shield to the ground pin 3 of the input connector, but do not
connect at the other end. Use driven shield pin 6 of the Input connector instead of pin 3 if attaching to pin 3
does not give the desired results. Inside the cryostat, tightly twist the sensor leads: V+ to V– and I+ to I–.
10-12
Lake Shore Model 340 Temperature Controller User's Manual
Model 3465 Input
Connector
1
I
–
2
V
–
3
Ground
4
V+
5
I+
6
Shield
Options and Accessories
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Troubleshooting
