Different types of temperature sensors

Designers of temperature monitors to alarm, log or protect equipment or areas can be built with many different types of temperature sensors.  The type of sensor a manufacture of a temperature monitors chooses is usually determined by his best guess as to where the monitor is to be used by the end user as well as his familiarity with the alternatives. 

The application usually determines the type of sensor

If he is building a monitor that will be used to monitor a refrigerator he might choose to use a thermistor because it has a high degree of accuracy over a narrow temperature range.  However if he is building a temperature monitor to alarm a cryogenic freezer he will almost certainly choose a thermocouple or an RTD. 

Choosing a thermocouple instead of an RTD could be based or price since a thermocouple is normally much less expensive than a RTD.  Neither an RTD or Thermocouple has good linearity and will require a lot of engineering and additional circuitry in the finished product. 

Analog vs. Digital

The choices of temperature sensors has expended in recent years to provide more choices for the design engineer.  For centuries all temperature sensors were ananlog devices. Analog sensors include the liquid-in-glass thermometers, and bi-metal strip thermometers, which are very low cost, are not extremely accurate and almost impossible to incorporate into multi-purpose instruments.  Analog sensors also include thermistors, RTDs and thermocouples, each of which have their plusses and minuses as shown in the table below.

Characteristic Thermistor RTD Thermocouple IC sensor
Temperature Range -100 to +500C -250 to +750C -200 to >+2000C -55 to +200C
Linearity Worst Good Poor Best
Accuracy Calibration Dependent Best Good Good
Sensitivity Best Less Worst Good
Power Consumption High High Low to High Lowest
External Circuitry Simple unless high accuracy/low power needed Complex Complex Simplest
Typical Applications Low precision, moderate temp range – refrigerators, freezers, rooms High precision, extended temperature – gas and fluid flow Extreme temperature sensing – super cold or cryogenic freezers. Refrigerators freezers, climate controlled rooms, etc...

Digital sensors are a fairly recent innovation which can be incorporated in many different types of temperature devices such as; temperature monitors, temperature alarms, data loggers and  temperature recorders of all types.  They have the advantage of providing the best linearity and accuracy as well as being lower cost than the analog alternatives and requiring the least amount of external circuitry.

Two Dimensional Instruments offers all the standard analog sensors listed in the chart above but we also offer a digital temperature sensor, which saves the end user money and offers superior accuracy in most cases.  Unless you need to monitor, alarm or log extreme temperatures we recommend the digital temperature sensor.  The digital sensor also offers increased stability, which translates into longer times between recalibration.

Designed and Manufactured in the USA

2009 Two Dimensional Instruments, LLC
(modified:October 21, 2019 12:10 PM)