Front Panel Operation - ILX Lightwave LDT-5412B User Manual

THERMISTOR MODE: A three position switch that adjusts the measurement and setpoint current
sources and also determines how the values are displayed on the front panel. The 10µA and 100µA
positions configure the sensor current source for the selected value and displays the value of the
setpoint and current sensor in k on the front panel. °C LINEARIZED FOR 10k is a special mode
that places a 10 k resistor in parallel with the thermistor to linearize the temperature response. The
front panel is calibrated to display the approximate temperature with an accuracy of ±1.0 °C in °C
when a 10 k thermistor is used as the sensor.
SET RESISTANCE: Allows the operator to bypass the set resistance function of the front panel and
externally control to a known resistance. When the switch is in the EXT position, the temperature is
controlled to match the resistance measured between pins 5 and 6 of the OUTPUT connector. This
mode is useful if always operating at the same setpoint. When the switch is in the INT position, the
external resistor is ignored and the front panel knob controls the temperature setpoint.
ANALOG OUTPUT: An isolated BNC connector is located on the rear panel of the LDT-5412B that
provides the capability to externally measure the voltage at the thermistor terminals. The nominal
gain of this connection is 10 mV/kΩ in the 10 µA range and 100 mV/kΩ in the 100 µA range. In the
linearized operating mode the voltage present at this connection mirrors the voltage present across
the parallel combination of the thermistor and a 10 kΩ resistor with 100 µA passing through the
combination. The nominal output impedance of this connection is 2 kΩ.
GAIN: A single turn potentiometer which adjusts the control loop gain. This adjustment affects the
slew rate and settling time of the LDT-5412B when reaching the desired setpoint. If the GAIN is set
too low (counter-clockwise,) the LDT-5412B will take longer to reach the desired setpoint. If the
GAIN is set too high (clockwise,) the LDT-5412B may oscillate around the desired setpoint. To
adjust, use a small blade screwdriver.

Front Panel Operation

This section describes the fundamentals of operation for the LDT-5412B Thermoelectric
Temperature Controller. The order of descriptions will follow the normal progression of how the user
would typically configure the instrument for use for the first time.
Figure 2.2 – LDT-5412B Front Panel
March 2013 7 LDT-5412B