Model 340 Cryogenic Temperature Controller

​The Model 340 has been replaced by the Model 350 and the Model 336. Input option cards still available for the Model 340 — please see the discounted equipment page.

Model 340 features

  • Operates down to 100 mK with appropriate NTC RTD sensors
  • Two sensor inputs; expandable to ten sensor inputs
  • Supports diode, RTD, capacitance, and thermocouple sensors
  • Sensor excitation current reversal eliminates thermal EMF errors
  • Two autotuning control loops: 100 W and 1 W
  • IEEE-488 and RS-232C interfaces, analog outputs, digital I/O, and alarm relays

The Model 340 cryogenic temperature controller is our most advanced temperature controller and offers unsurpassed resolution, accuracy, and stability for temperature measurement and control applications to as low as 100 mK. Operating with diodes, platinum RTDs, and negative temperature coefficient (NTC) resistor sensors, the Model 340 is expandable to ten sensor inputs or to operate with thermocouple or capacitance sensors. It has two control loops, with the first loop powered to 100 W. More information on Model 340 Cryogenic Temperature Controller...

Additional Inputs Still Available For the Model 340

The following optional inputs are available for the Model 340. Only one can be installed at a time, and the standard inputs stay in the instrument and remain fully functional. Calibration for the option is stored on the card so it can be installed in the field without recalibration. Limited numbers of these cards are still available on our discounted and discontinued product page and have been discounted to encourage existing Model 340 users to expand the functionality of their instruments.

3462 Dual Standard Input Option Card

Adds two standard inputs to the Model 340, appearing on the display as C and D. The card has separate A/Ds and excitation for each sensor. A microprocessor on the card manages the A/D and communication with the Model 340. Allows the Model 340 to read four sensors and use any of them as a control sensor.

3464 Dual Thermocouple Input Option Card

Adds two new thermocouple inputs to the Model 340, appearing on the display as C and D. The card has separate A/Ds and excitation for each sensor. A microprocessor on the card manages the A/D and communication with the Model 340. Thermocouple inputs range from cryogenic temperature to 1000 °C, with built-in room temperature compensation. Curves for thermocouple types E, K, and AuFe 0.07% vs. Cr are included. The user can add other types.

3465 Single Capacitance Input Option Card

Adds a new capacitance input to the Model 340, appearing on the display as C. The card has separate A/D and excitation for the sensor. A microprocessor on the card manages the A/D and communication with the Model 340. The 3465 is intended to control temperature in strong magnetic fields using a Lake Shore Model CS-501 capacitance temperature sensor.

3468 Eight Channel Input Option Card

Adds eight sensor inputs to the Model 340. The optional inputs are broken into two groups of four and appear on the display as C1–C4 for Input C, D1–D4 for Input D. The 3468 includes two A/D converters, one for each group of four inputs, and individual excitation for each sensor. Each input group must use the same sensor type, but the two groups can be different. The multiplexed inputs provide new readings for all eight inputs twice each second. The 3468 inputs are not recommended for temperature control because the reading rate is too slow to provide good stability.

A variety of sensor types are supported by the Model 3468, but not as many as the standard inputs. Diode and platinum configurations have similar specifications to the standard inputs, reduced only slightly to account for multiplexing. However, the NTC RTD configuration is quite different than the standard inputs. The option has a limited resistance range of 7.5 kΩ with a fixed current excitation of 10 µA. This limitation significantly reduces the low temperature range of the inputs. The option also does not support current reversal to reduce the effect of thermal EMF voltages. The original standard inputs remain fully functional allowing the Model 340 to measure 10 sensors when the option is installed.

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