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Model 340 Temperature Controller

Input Reading Capability Sensor inputs are read continuously with a high resolution analog-to-digital converter (ADC) that is dedicated to thoseinputs. Data from the ADC is converted to temperature using atemperature response curve for the sensor. Temperature readings and sensor units readings are available for every inputand can be displayed, sent over computer interface or used forone of the many built-in features of the Model 340. New readings are taken as often as 20 times a second; the update rate isslower for more complex readings. The display update rate isfour readings per second, but readings are available at full speed over computer interface.

? Front panel configurable for Lake Shore manufactured orother sensors

Temperature Response Curves and CalCurves™

? Supports most diodes, Platinum RTDs and Negative Temperature Coefficient (NTC) resistor sensors

A temperature response curve is needed to convert sensorreadings to temperature. Some types of sensors share the sameresponse and have a standard curve. The Model 340 includes standard curves for several sensors. If an application requiresmore accuracy or a standard curve is not available, a specificcurve must be loaded into the instrument for an individually calibrated sensor. Lake Shore offers a broad range of calibratedsensors and a CalCurve™ service that helps get calibration datainto the instrument. The Model 340 provides several ways to load curves from Lake Shore calibrations or user supplied sensors.Curves from any source can be entered from the front panel orover computer interface. CalCurves™ sold with Lake Shore calibrated sensors can be installed at the factory whenpurchased with a Model 340, or they can be field installed usingthe data card slot.

? Two soft configurable sensor inputs included ? Two temperature control loops ? 100 watt heater output on first control loop (1 watt on 2nd loop)

SoftCal™

? IEEE-488 and serial interfaces, analog, digital I/O and alarm relays

SoftCal™ is a good solution for applications that need moreaccuracy than a standard curve but do not need traditionalcalibration. SoftCal™ is an algorithm that utilizes the predictability of standard curves to improve the accuracy of anindividual sensor around a few known temperature referencepoints. SoftCal™ generated curves can be purchased with some types of sensors. The Model 340 also generates SoftCal™curves for diode and Platinum RTD sensors.

? One-button control for all major functions ? Bright LCD graphic display that is user configurable After 30 years of leading the way in cryogenic measurement and control,Lake Shore has fully utilized this experience with the Model 340, our most advanced temperature controller to date. The Model 340, offeringunmatched features, has not lost sight of its primary functions: accuratetemperature measurement and stable temperature control.The Model 340 is a 32-bit microprocessor-based temperature controllerwith two independent inputs. It operates with nearly any diode, Platinum RTD or Negative Temperature Coefficient (NTC) resistor sensor. Thecontroller’s 24-bit analog-to-digital converter and low noise circuit designgive temperature readings with resolutions as low as 0.1 mK at 4.2 K. The Model 340 is a two loop controller with the first loop powered to100 W and a second independent control loop used to reduce thetemperature gradients in one cooling system or run a second separate cooling system.The Model 340 has the best display capability and provides the mostoperator feedback of any Lake Shore instrument. The controller’s liquidcrystal display can show up to eight different readings simultaneously,including temperature and sensor units and math functions. Internal memory can store up to forty 200-point curves. Additionally, the datacard feature makes it easy to replicate conditions from one day to thenext, from one system to another.

PID Control The Model 340 uses a Proportional, Integral, Derivative (PID) control equation to calculate the necessary heater output basedon the temperature setpoint and feedback from the sensor

Model 340 Temperature Controller

Configurable Inputs Each of the many different types of temperature sensors has qualities that make it the best choice for some application.The Model 340 has the ability to operate with many differenttypes of sensors, so that it is not a limiting factor when deciding which sensor to use. The two sensor inputs includedin the Model 340 can be configured to measure and controlwith nearly any diode or resistive sensor. Appropriate excitation and input gain can be selected from the front panel.There are no modules or cards to swap or internal switchesto change. Negative Temperature Coefficient (NTC) resistive sensors that change many orders of magnitude are measured in an autorange mode that keeps the power in thesensor low to reduce self heating. Automatic current reversal for NTC resistors eliminates the effect of thermal EMF with roundedsquare wave excitation. For special applications, any availableinput gain and excitation can be selected manually. An option card is required to read sensors other than diodes and resistorsor to read more than two inputs continuously.