Applying Thermistor Technology in Real World Applications
The combined flexibility and variety of configurations and protective coatings available for NTC thermistors allow the devices to be successfully used in a variety of applications including those within medical, aerospace, industrial, HVAC&R and instrumentation. Below is a sampling of some of these applications.
Instrumentation Applications.Thermistors available are also available as surface-mount devices for general temperature sensing and compensation network applications. Thermistor chips are suitable for laser diode compensation, infrared measurement compensation, battery packs and temperature sensing at board level.
Medical Applications. Patient monitoring, diagnosis and treatment are the primary medical applications for NTC thermistors. Probes can be configured as disposable devices or as reusable ones -- the latter being able to withstand steam sterilization by autoclave. Patient monitoring applications typically have operating ranges from 32 to 122°F (0 to 50°C) with accuracy of ± 0.1°C. FDA, CE and MDD approvals are required and attainable for use with core-temperature monitoring, multi-parameter monitoring, incubators, infant warmers and respirators. Diagnostic and treatment applications typically have an operating range of 32 to 212°F (0 to 100°C) with an accuracy of ± 0.1°C. Specific applications include catheters, ablation thermodilution, urology, oncology, thermography and blood oxygenation.
Aerospace Applications. ESA- and NASA-approved NTC thermistors are available for operating temperature ranges of –67 to 239°F (-55 to 115°C) with an accuracy of ± 0.1°C available. Because footprint is critical, probes are less than ~1" (2.4 mm) in diameter. Uses include monitoring of the temperature of space station batteries, precise monitoring of the temperature of the joints in the robot arms of the space station, as well as monitoring of solar panels and instrumentation control in aerospace applications.
HVAC&R Applications.Standard glass-coated or miniature glass-coated thermistors commonly are used for HVAC&R applications. Standard glass-coated thermistors are used for operating temperature from of -67 to 572°F (-55 to 300°C) with accuracies of 5, 10 and 20 percent interchangeable or 1 percent to 5 percent point matched. Thermistor components are used in standard thermostat applications; specialized single-use probes are used for balancing air flow in HVAC ducts in modern office buildings; overmolded parts are used in grocery stores and food-vending machines; and stainless steel probes are used for monitoring food and drugs during refrigerated transport, just to name a few.
Miniature glass-coated thermistors attain comparable accuracy over a range of -112 to 617°F (-80 to 325°C). Common uses include sensors for engine temperature control, hot water boiling systems, air conditioning systems, and refrigeration control. The low mass, fast time response, high stability and high temperature capabilities of the miniature glass parts make them useful for measuring gas flow and fluid properties. Some specific applications include measuring gas flow in gas meters, measuring mix ratios in soft drinks, measuring specific gravity, or the fat content, of milk.