Bead type thermistors are often fabricated by applying a slurry of mixed metal oxides with a binder onto two spaced platinum alloy lead wires. Using the proper binder is essential to create a proper surface tension that draws the material into the bead (shaped like an ellipsoid). Lead wires are strung into fixtures that applies a small amount of tension. This carefully controls the spacing between wires. Once the mixture has dried, beads are removed from the fixture and then sintered.
Bead-type thermistors are often used because they offer high stability, fast response times, and they can operate at high temperatures. Because they come in small sizes, they exhibit low dissipation constants. When compared to metalized surface contact type thermistors, bead-type thermistors are typically less expensive.
The two most popular types of bead-types thermistors are:
Glass Coated BeadsIf the glass seal remains intact, these thermistors offer great stability. Glass coatings are thin, which means they can be ruptured during handling
Miniature Glass ProbeThese thermistors have a longer body than the above bead-type thermistors. This long body makes it easy to handle. They are ideal for applications that require fluid immersion. They have a longer seal along with the leads, which adds to the stability.
Sensor Scientific, Inc | All Rights Reserved