The Perfect Temperature Sensor:
Has no effect on the medium it measures
Is precisely accurate
Responds instantly (in most cases)
Has an easily conditioned output
Regardless of the sensor type, the above concerns affect all temperature sensors.
The biggest concern when measuring anything is to ensure the measuring device
itself does not influence the media it is measuring. With contact temperature
measurement, this is especially important. Choosing proper sensor size,
encapsulation and lead configuration are key design concerns to reduce “stem-effect” and other measurement errors.
Once minimal effect of the measurement media is accomplished, how accurately you
can measure the media becomes important. Accuracy incorporates basis sensor
characteristics, measurement accuracy, etc. The most accurate sensor is useless
if design concerns around stem-effect are not addressed.
Response time, or how quickly a sensor is indicate temperature, is dependent on
the size and mass of the sensor element, with some influence by leads. The smaller
the sensor, the faster the response time. Semiconductors are the slowest
responding. Platinum wirewound elements are next slowest. Platinum film,
thermistors and thermocouples are available in small packages, and thus have high-speed options. Glass micro-beads are the fastest responding thermistor
While purchasing agents are looking for the least expensive part possible, engineers
recognize the importance of the value the sensors offer for the sensor dollar spent.