Thermistors for Medical Applications

Thermistors for Medical Applications have, for decades, and are still relative and reliable  which this field demands. Thermistors sensitivity and interchangeability are the necessary charateristics required for monitoring patient temperature. Patient temperature is measured using thermistors that are packaged in variety of probes such as skin(surface) rectal, esophageal and catheter probes for subcutaneous applications.

NTC thermistors are also used for measuring flow in inserted devices.  A pair of matched thermistors can be attached to the tip of a catheter which can be guided to different locations of the heart to measure blood flow. Either they can be heated by a coil of flushed with cold saline to measure blood flow rates. . When flushed with cold saline, the first sensor gets cooled more than the second because the blood flow warms up the saline that reaches the second sensor. . Since the two thermistor sensors are seperated by a known distance and the temperature and the volume of saline is controlled, the blood flow can be calculated by reading the outputs of the two sensors. When cold saline is used these thermistors do not require external power.

Catheter ablation sensors are another example of sensors temporarily inserted through incision to effect specific treatments and/or to take measurements during treatments. Ablation is the process  of selectively killing tissue  to create scar tissue in order to re-route  nerve impulse flow within the heart to correct abnormal arythmias. RF energy is often used in the ablation process. It is critical that the force applied by the catheter tip to the target tissue not exceed predetermined  values to avoid  any possibility of perforating the target tissue.



Thin Film NTC Thermistor

ntc thermistorThermal Component Technologies has released a new Thin Film NTC Thermistor. The Thin Film NTC Thermistor are frequently used for applications where space is a concern and standard design are not thin enough. With a typical thickness of 0.55mm offers the solution engineers have been looking for. They are an ideal choice for precise temperature measurement between flat surfaces where quick time response is critical. The thermistor chip is loaded between 2 conductors then sandwiched with polyimide insulation. This provides excellent moisture resistance, along with flexibility. All the usual benefits of thermistors where sensitivity to temperature change is paramount.

Applications Thin Flim NTC Thermistor

where this type will suit is in the medical industry such as blood bag temperature monitoring for refrigerated storage. Small battery packs will also demand this type where space is particularly limited and quick response is need to prevent heating during charging cycles. Surface temperature of pipes can also be monitored using thin film technology.

ntc thermistor

Glass Probe Thermistor


Glass Probe Thermistor – 8 Series

Ever had problems sourcing what thermistor to use in caustic liquid enviornments?

Solutions have been available, but never quite offering a device with a repeatable tight tolerance.

Thermal Component Technologies Glass probe 8 series thermistor are glass devices with standard electrical characteristics similar to the standard Glass A and B series thermistors with a 1% tolerance, however offering a longer sheath for direct immersion into liquids . The glass encapsulation offer superior stability and durability over time. The 8 series thermistor range is offered with dumet wires with/ without polyimide tubes for insulation. These NTC probes are ideal for harsh enviornments and suitable for potting into brass or stainless steel housings for locating in containers etc. They also offer the advantage of high temperature situations remaining stable to 325C, tolerating intermittent maximum of 550C. Series 8 offers thermistor sensitivity at high temperatures.

Design Engineers will appreciate the variety of applications that they will be able to use these probes for such as medical and chemical and will be especially suitable for laboratory temperature monitoring.

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Technical Update:

  • Resistance @ 25C  –  1K ohm ~ 231K ohm
  • Tolerance                –  from 1% ~ 20%
  • Beta Value               –  from 2668 K~ 4535 K
  • Temp range                   -50C ~ +300C

  • Long glass probe offers moisture resistance for direct immersion
  • Resistance to  most chemicals
  • Available in custom probes
  • Interchangeable
  • HVAC
  • White Goods
  • Industrila. Instrumentation
  • Chemical Industry
  • Medical