Linear Response Components
For applications requiring thermistors with linear response to temperature change, OMEGA offers linear components. These unique devices consist of a thermistor composite for temperature sensing and an external resistor composite for linearizing.
Thermistor composites 44018 and 44019 each contain two thermistors packaged in a single sensor ( PDF Figures 1A & 1B). Thermistor composite 44020 contains three thermistors packaged in a single sensor (PDF Figure 1C).
Resistor composites for use with 44018 and 44019 thermistor composites consist of two metal film resistors of the size shown in Figure 2. Resistor composites for use with the 44020 thermistor composite consist of three of the same type metal film resistors.
Linear components are manufactured with different values for different temperatures ranges. When they are connected in networks shown in Figures 3 and 4, they produce a varying voltage or resistance which is linear with temperature.
One of the basic network manifestations is a voltage divider as in PDF Figure 3A for components other than #44212, and as shown in PDF Figure 3B for component #44212. The area within the dashed lines represents the thermistor composite. The network hookup for linear resistance versus temperature is shown in PDF Figure 4A for linear components except #44212, and in PDF Figure 4B for #44212.
Multiplexing
The 44018 thermistor composite is used in four of the linear components. The part that changes in each component is the resistor composite, which determines the temperature range. Therefore, the 44018 thermistor composite can be used over the entire -30 to 100°C temperature range by simply changing resistor composites. Its accuracy and interchangeability over the full range is ±0.15°C. It is not mandatory that OMEGA™ resistor composites be used with the 44018 thermistor composite. Any 0.1% resistors of the proper values and with a temperature coefficient of 30 PPM or less may be substituted. In other situations, it is frequently desirable to have thermistor composite temperature sensors at more than one location. When this is required, it is not necessary to have a separate resistor composite for each thermistor composite. It is possible to multiplex any number of thermistor composites through a single resistor composite for greater design flexibility.