Achieve Precision Temperature Control With Tec Seebeck-voltage Sampling

摘要

TEC (thermoelectric-cooler) temperature-control systems often have limited stability. The causes of these limitations are the thermal properties of the system, not the performance of the control electronics. Real-world thermal-control systems incur nonzero thermal impedances in the heat-transfer paths between the TEC; the thermal load, which is the object of thermostasis; the temperature sensor-for example, a thermistor; and the ambient temperature.rnIf the ratios of these impedances don't balance, then even perfect thermostasis of the sensor's temperature doesn't equate to adequate stability of the load's temperature. The circuit in Figure 1 provides a thermoelectronic design that directly measures the heat flux through the TEC and then uses the measurement to better estimate and cancel the effects of thermal impedances. Its operation is based on the fact that the total voltage that every TEC develops is the sum of two components: an ohmic component proportional to drive current and the Seebeck voltage, V_S, which is proportional to the temperature difference across the TEC and, therefore, to heat flux.