Control Capability of the LDC-3916371 Fine Temperature Resolution Module

The standard TEC modules for the LDC-3916 mainframe use a 16-bit ADC for temperature measurement and a 12-bit DAC for the temperature setpoint. The result is that the module can measure temperature with a much finer resolution than it can set the temperature. This design method is preferred over the alternate, whereby the control resolution is finer than the measurement resolution. The second method results in a greater degree of measurement uncertainty, which means the user will not necessarily know the actual temperature of the load even though the apparent set point resolution is very good.

The LDC-3916371 Fine Resolution Temperature Control module uses a 16-bit DAC for the temperature setpoint, so it is capable of setting the temperature to a much finer resolution than the standard TEC modules. On the LDC-3916371 module, the theoretical setpoint resolution matches the measurement resolution; both are 16-bit converters. [more]

Thermistors change their resistance with respect to temperature. Typically, the resistance will decrease with increasing temperature. IC sensors, on the other hand, generate either voltage or current outputs that vary with respect to temperature. The two most common IC sensors are the Analog Devices AD590, which produces a linear output of 1A/K and the National Semiconductor LM335 Series, which produce a linear output of 10mV/K. These IC-I and IC-V sensors are a good choice when the temperature of a circuit board must be monitored since they can be mounted using standard PCB assembly techniques. These sensors are also a good choice when moderate accuracy is all that is required.

One of the main differences between IC sensors and thermistors is the fact that the IC sensors require an external power source to function. For example, a handheld multimeter is all that is required to measure the resistance of a thermistor to determine its temperature. Depending on the sensor, the IC sensors need either a current source or a voltage source in addition to the multimeter to measure temperature. Furthermore, the output from both sensors is relatively linear while a thermistor's resistance change is nonlinear. This can be seen in the graphs taken from the manufacturer's datasheets.

Finally, the working temperatures, recommended by the manufacturers of the IC sensors, range from -55C to +150C. Typical thermistors are designed for use up to approximately 80C although special high temperature versions are capable of measuring temperatures beyond 300C.

• Analog Devices
• National Semiconductor - Precision Temperature Sensor
• Technical Glossary
• Feedback and Temperature Control