The accuracy of a PID controller depends on two key factors: the precision of the PID algorithm used by the process controller, and the reliability of the input data that it is working with. Tecnologic supply a wide variety of custom sensors designed to deliver accurate data on a range of input types including temperature, humidity, fluid level, presence & proximity, speed and more.
In this article we provide an overview of the main sensor types available, how they work and some of their typical applications.
Temperature sensors are at the heart of our range and are designed to be used in conjunction with PID temperature controllers. The physical design and temperature range catered for can vary greatly according to the application and especially the physical characteristics of the environment being sampled. The key categories are:
PT100 Elements – These sensors typically consist of a flat film of Platinum (Pt) placed over a ceramic base and then sheathed for protection. Changes in temperature cause the resistance of the Platinum element to change in a very predictable way, resulting in a high level of accuracy, and the value of this resistance can be fed into a PID controller. Our controllers can accept PT100 sensors within a range of -200 to +850C although the high temperature use is very rare.
Thermocouples – This type of temperature sensor involves joining two different metals together at one end and measuring the change in voltage that occurs in response to a change in temperature. We offer K, J, S, R and T type thermocouples designed to operate between 0 and +1760C, all of which are compatible with our range of PID temperature controllers.
Our thermocouple sensors are available either in rigid or flexible form, depending on how the sensor is intended to be installed. Flexible format thermocouples allow the temperature probe to be bent to any shape as required by the application.
The thermocouple junction may be either covered or exposed depending on application requirements. Exposed junctions offer a faster response time but are only practical in situations where damage of the joint due to corrosion, impact or pressure are not expected.
We can supply PT100 or thermocouple sensors with a connection head with an IP rating of 68, providing a high degree of protection. The head can accommodate a transmitter if desired, enabling the sensor to operate wirelessly.
Thermistors – These are digital temperature sensors which use the change in electrical properties of a semiconductor when exposed to heat, to generate a digital temperature signal directly. Their advantage over the analogue sensors described above is their small size, and their high level of sensitivity. We offer both PTC (Positive Temperature Coefficient) and NTC (Negative Temperature Coefficient) devices which are intended for use with our TLZ range of digital thermostats. However they can also be used with general PID controllers from our range.
Many industrial processes require the levels of moisture in the air to be controlled for a variety of reasons, and for processes to be stopped or alarms triggered if humidity falls outside a specified range.
The sensors use the changes in electrical properties (either capacitative or resistive) that occur in the presence of different levels of moisture, to generate a signal proportional to the humidity of the surroundings.
With industrial applications and component reliability and longevity in mind, our sensors are built with IP ratings commensurate with the humidity range being monitored. For example, the TRH10 is designed to measure humidity up to 90% and has an IP rating of 54; while the TRH11 and TRH12 are designed to measure up to 100% humidity and therefore have a higher IP rating of 65.
Magnetic Proximity Sensors
Via our partner Celduc Relais we can supply magnetic sensors designed to detect and measure a wide variety of physical properties including:
Fluid levels – Detects whether a container has finished filling or is below a minimum level. This is useful for checking fuel levels, providing overflow warnings and so on.
Presence, Proximity and Position – Detects whether an object or person has come within a specified distance of the sensor. This has applications in manufacturing and packaging where a piece of machinery needs to know whether an object is in position ready for a particular part of the process to proceed (e.g. dropping a product into a waiting container). There are also myriad safety applications such as detecting whether there are people or objects in the vicinity that should or should not be, detecting when a moving object is getting close to a particular location (e.g. whether a lift has reached its intended floor) or detecting when a door is securely shut (e.g. in a car or airplane).
Speed – Detects how many times a particular point on a rotating object moved past it within a period of time, such as gear wheels operating machinery or an axle in a vehicle. Outputs can be used to provide feedback to users, feed into subsequent processes or trigger specific alarms or stop points.
The mechanism used to detect all these properties is a floating magnet which, when it changes position, causes variations in the magnetic field and hence electric changes.
Magnetic sensors are available in a variety of housing materials, enabling usage in a wide range of fluid types including chemicals and fuels; and in a variety of housing configurations depending on how the sensor is to be incorporated into a system (e.g. screw fixing, pin attachments for PCB boards etc). A number of other attributes can be specified to produce exactly the design of sensor you need, such as detection distance, operating current or voltage and so on.
Bespoke Sensors from Tecnologic UK
If what you need to measure isn’t mentioned here, or you need a specific variation in design, please call us as we can almost certainly help.
Our team of experts can take into account the PID controller you intend to use (i.e. what output characteristics the sensor needs to have) and other requirements of your application (e.g. accuracy levels required, usage patterns and so on) and help specify, design and build a sensor to meet your exact requirements.
Just call our team on 01252 377 600 or complete our contact form.