With systems incorporating sensors at the heart of key operating processes such as quality control, personnel safety and presence detection in modern manufacturing facilities, warehousing and process environments, selecting the right sensor for the right application has never been more important. Particularly as the correct sensor specification can positively contribute to an improvement in quality, energy savings and manufacturing speed and volume, in turn having a significant impact on a business. By Phil Dyas, sensor specialist, SICK (UK)
The wide range of industrial sensors increases every week to meet the growing number of application needs. This growing capability makes it ever more important to select the right sensor for the individual project requirements.
For example, we often find that production or packaging line machinery is modified to suit the sensor limitations rather than the other way around. Many manufacturers will vocalise concerns about the sensors, but make limited investigation of the vast range of sensing systems on the market. However, this variety, combined with the sensor manufacturers’ ability to modify a sensor to meet exact application needs, means the sensor can and should be specified to meet individual project requirements; altering the machinery is far more expensive.
The resources of an advanced and comprehensive product range can be advantageous in delivering off-the-shelf solutions. But, very often, simple modifications can achieve a best practice solution at little or even no cost.
Best practice solutions are essential where sensors control critical points of production. Otherwise an unsuitable solution can allow faulty products through, cause line outages, and affect timing and phasing, resulting in poor margins and unforgivable product and energy wastage.
Green thinking
The environment where the sensor will operate and how this could affect the operation of the sensing system is key to ensuring optimal performance. The environmental conditions of each production facility, which might include exposure to high frequency lighting or EMC, for example, can have a significant impact on the type of sensor specified.
It’s important to examine how these environmental factors might affect the performance of certain sensor types. For example, sensors deployed on a logistics site, where mobile phones or two way radios are in use, must be able to eliminate errors and false operation caused by radio frequency emissions. High frequency lighting and even flashing beacons on forklift trucks can also cause spurious triggering of optical sensors.
Low temperature operation
Sensors used in cold store environments can be exposed to temperatures as low as -40°C. If located near a door, where the temperature is likely to rise periodically, condensation may occur on the lens, which could also freeze and ice over when the temperature drops again. To counteract this, sensors with heated lenses and heated reflectors should be considered. The type of cabling must also be considered; PVC cabling is commonly used on sensors, however, this is not suitable for extreme cold as PVC turns brittle at low temperatures.
High temperature adaptation
Specifying sensors for high temperature environments, such as the steel and glass industry, also poses unique issues. Most sensors have an operating temperature limit of 70°C, which is far exceeded in such environments. Specifying a sensor with cooling plates and high temperature reflectors can extend the operating envelope to around 100°C. Specifying a metal housing and glass lenses as opposed to plastic will also combat any issues with melting.
Vibration modification
In environments where conveyor belts are in operation, excessive vibration can cause sensor misalignment and where forklifts are used the likelihood of knocking a sensor is increased. Specification for such environments should include a high-strength wrap around bracket providing protection against physical damage and protecting the electrical supply connection.
Conclusion
By specifying sensors with familiar performance parameters, the ‘comfort zone’, rather than seeking a sensor which is fully fit for purpose, engineers may be avoiding confronting the complexities and variety of sensors currently available.
Selecting a sensor which is not absolutely right for the job will have a significant impact on productivity, quality, maintenance and inventory, as well as cost. Therefore an in-depth understanding of the range of sensors available, and the impact of operational conditions, is essential when specifying.
