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Lake Shore Model 325 Temperature Controller User’s Manual
3-4 Installation
3.4 DIODE/RESISTOR SENSOR INPUTS
This section details how to connect diode and resistor sensors to the Model 325 inputs. Refer to Section 4.4 to configure
the inputs. The optional thermocouple input is described in Section 3.5.
3.4.1 Sensor Input Connector and Pinout
The input connectors are 6-pin DIN 45322 sockets. The sensor output pins are defined in Figure 3-3. Two mating
connectors (6-pin DIN plugs) are included in the connector kit shipped with the instrument. These are common
connectors, so additional mating connectors can be purchased from local electronics suppliers. They can also be ordered
from Lake Shore (P/N 106-233).
NOTE: Pin 3 should not be used for new installations. However, to match existing Model 321, Model 330, or
Model 340 connector wiring, the definition of Pin 3 may be changed with a jumper. See Figure 8-8
for jumper location.
To provide compatibility with sensor input connectors that have been wired for Lake Shore Models 321, 330 or 340
Temperature Controllers, Jumper 4 (for Input A) and Jumper 7 (for Input B) are used to select the function of Pin 3 of the
connectors. The Model 321 and the Model 330 each provide a constant 1 mA sensor excitation current on Pin 3 and
10 µA current on Pin 5. The Model 340 provides both 1 mA and 10 µA excitation current on Pin 5 and connects Pin 3 to
sensor ground reference. If the sensor being used was wired for use with a Model 321 or a Model 330, the jumper should
be placed in the 321/ 330 position (factory default). This provides the output current selected via the front panel input
setup function on both Pins 5 and 3. If the sensor was wired for use with a Model 340, the jumper should be placed in the
340 position. This provides the output current on Pin 5 only and connect Pin 3 to sensor ground reference.
Pin Symbol Description
1 I–
– Current
2 V–
– Voltage
3
+1 mA – Model 321/330 Configuration
Shield – Model 340 Configuration
4 V+ + Voltage
5 I+ + Current
6 None Shield
Figure 3-3. Diode/Resistor Input Connector
3.4.2 Sensor Lead Cable
The sensor lead cable used outside the cooling system can be much different from what is used inside. Between the
instrument and vacuum shroud, error and noise pick up, not heat leak, need to be minimized. Larger conductor, 22 to
28 AWG stranded copper wire is recommended because it has low resistance yet remains flexible when several wires are
bundled in a cable. The arrangement of wires in a cable is also important. For best results, voltage leads, V+ and V–
should be twisted together and current leads I+ and I– should be twisted together. The twisted pairs of voltage and
current leads should then be covered with a braided or foil shield that is connected to the shield pin of the instrument.
This type of cable is available through local electronics suppliers. Instrument specifications are given assuming 10 feet of
sensor cable. Longer cables, 100 feet or more, can be used but environmental conditions may degrade accuracy and noise
specifications. Refer to Section 2.3.6 for information about wiring inside the cryostat.