Precise fluid temperature measurement is key in a wide range of industrial procedures such as food manufacture, distilling and brewing. It is also an essential factor in various medical applications.
This task is typically performed by a type of temperature sensor, making direct contact with the relevant fluid. This sensor will typically consist of a probe attached to a connection head with a lead out of the storage tank.
Due to the massive variety of applications, these are used for, several different types of temperature sensors are available. In some circumstances, it is necessary to use a custom temperature sensor to perform this task.
What are custom temperature sensors?
Custom temperature sensors work by measuring electrical resistance relative to the temperature of the surrounding fluids. As the temperature within the fluid changes, the electrical resistance also changes, with higher temperatures causing an increase in resistance.
This allows for the extreme precision essential for many food processing and medical applications.
A variety of connection and mounting systems are required to fit every purpose, to monitor and signal temperature changes accurately. There are some different types of temperature sensor:
- RTDs (Resistance Temperature Detectors)
- Thermistor Temperature Sensors
- Semiconductor Temperature Sensors
- Vibrating Wire Temperature Sensors
Of these many types, many custom temperature sensors are Resistance Temperature Detectors.
Resistance Temperature Detectors
All electrical conductors, (though in the case of RTDs it is often a metal element) have an electrical resistance, which is a measure of how easily electricity flows through it. Any temperature changes will alter the resistance, which can then be calculated by knowing the resistive properties of the element.
The choice of material used for the element will vary according to many factors, most commonly the range of temperatures involved, and the temperature that the fluid will reach.
Platinum RTD Sensors
Ideally, this material will be chemically inert, highly stable and can function over a wide range of temperatures. For this reason, platinum is the metal of choice, especially because of the linear relationship between temperature and its resistance. This linear relationship (where a temperature rise is consistent with a change in resistance) makes the process of calculating temperature reading simpler.
However, the cost of using a metal like platinum means that other alternatives are sometimes used, but each has its own drawbacks.
Other materials used in custom temperature sensors
Nickel is also used for temperature sensors as a cheaper alternative to platinum, however, is less accurate over higher temperatures and corrodes over time. Copper is also used as it has a similar linear temperature/resistance relationship as platinum. However, this cheaper material has a much more restricted measurement range.
For this reason, a variety of solutions are needed, according to the requirements of the operation. When you consider the range of different tanks or vats that are used, the fluids contained within them and the temperature ranges that have to be monitored, it can be easy to see why custom temperature sensors are frequently required.