Which measurement technology? A basic guide to help in the selection of the correct sensor type

Linear Position Sensors

When deciding which sensor technology is suitable for your measurement application, the first consideration is whether you need to measure linear or rotational movement (sliding or rotating sensor operating shaft). The second consideration is the output signal required, absolute or incremental (analogue or encoder). If you require a signal that specifies a unique measurement position then you will require a sensor with an absolute output. Absolute output usually means that the unique measurement position is held electro-mechanically by the sensors operating shaft. Magni-Tec® Sensing Technologies manufacture contactless position sensors with an absolute output signal, as the majority of high performance control and measurement systems require signals of this type. Incremental devices typically need to be re-calibrated when powered up and this procedure can be impractical in most applications.

Rotary Position Sensors

The operating environment of the application will have an impact on the measurement technology choice. Consideration should be given to possible temperature changes and the presence of any shock loads and vibration. The presence of any moisture or fluid will also dictate the level of sealing required for the sensor housing (IP rating). Any moisture ingress will have an adverse affect on the sensors operational life. The application may have other unique environment aspects such as high pressures or the presence of corrosive chemicals. The measurement range of Magni-Tec® sensors varies from a few millimetres to hundreds of millimetres, or 1° to 360° of rotation. Accuracy, which typically has the components of non-linearity, repeatability, resolution, hysteresis and thermal drift are usually stated on the manufacturers data sheet. For many applications repeatability and thermal drift are the most important components. All sensors when operated at elevated temperatures will exhibit some unwanted increase in the output signal caused by temperature. The drift is caused by material property changes and the expansion of the sensors electrical and mechanical components. The accuracy of a sensor is normally specified in absolute units, i.e. millimetres or microns, or in relative units such as percent of full-scale measurement.

Linear Position Sensors

You will need to ensure the sensor, and also the control or data-acquisition system has adequate sampling rates to record the resulting data. Also, as the sensor is going to be a part of a measurement or control system, determine the preferred electrical input and output signal requirements. The usual choices are analogue inputs, typically 5V or 8 to 30V, and outputs signals of 5V or current (420mA), or digital (PWM, CAN and RS485). Ensure you consider additional accessories that maybe required, for example, special signal-conditioning electronics, electrical connectors or mounting fixtures.

Choosing the correct contactless measurement technology should become self evident after determining your requirements from the above information. If you require additional information regarding technology selection, please do not hesitate to contact our technical team: contact us