Certain medical equipment requires “instant on/instant off” temperature control. IRC has developed a series of thick film planar resistive heating elements on insulated stainless steel substrates that deliver such a feature. Based on Thick Film on Steel technology (WDBR), the heating elements replace conventional heaters with an intrinsically safe, flameproof planar device that can be formed in almost any flat shape to deliver precise heating control for blood transfusion warmers, humidifiers for sleep apnea systems, and medical sterilization equipment.
Proprietary thick film resistive elements and a rugged ceramic dielectric glaze are directly applied to a stainless steel substrate. The resulting device is robust with excellent thermal transfer characteristics. The stainless steel heating element can then be designed directly into the medical equipment. Fuses and thermistors can be integrated directly into the heating elements for additional over-temperature protection as well as closed-loop feedback. The technology is also available on 300 series stainless steel tubular substrates from 0.5 in. to 2.25 in. OD for direct heat transfer to fluid flow.
The thick film-on-steel device can also be used as a high power surge resistor to suppress loads such as dynamic motor braking, inrush current limiting, and capacitor discharge applications. Medical applications for this version of the resistors include use as a low-pass filter in MRI and CT scanners to improve image definition by suppressing EMI; and as a line load control to reduce power to surgical lasers during idle periods before powering down.
In addition to the custom designs available for specific medical applications, the resistor technology is offered in several standard configurations rated for 0.5 kW, 1.0 kW, 2 kW, 3 kW, 5 kW and 7 kW (maximum pulse power rating). Standard resistance values range from 12 ohms to 150 ohms, with tolerances to +/-10% (custom resistance values and tolerances are available). Minimum dielectric withstanding voltage is specified at 2500 Vdc. Inductance values range from less than 3 µH to less than 6 µH, with a continuous operating temperature rated to 400° C.
Filed Under: Semiconductor, Electronics • electrical, Resistors