A simple low-cost, thermistor-based, local air-velocity mapping method (PCB modules)

A method is presented for using interchangeable thermistors as local air-velocity transducers for the thermal verification of electronic assemblies. Because of their small size, thermistors are ideally suited for local velocity measurements in hard-to-reach places, and do not interfere with the phenomena being measured. Accuracy is acceptable in the velocity range from 0 to 600 ft/min, in the ambient temperature range from 20 to 45 degrees C, and the cost is lower than that of other sensors. Because the thermistor is intrinsically a temperature sensor, it can also double as a local air-temperature transducer. Thermistor signals are high level, and therefore easier to read than those from other types of transducers such as thermocouples or transistor junctions, and no reference temperatures or precalibration are required. Used in conjunction with data logging equipment and a computer, a printed-circuit module is produced, displayed, and stored. These data are intended for use with proprietary software to predict individual board component junction temperatures and failure rate.<>