If you are taking your baby steps into engineering, then you may have come across the term ‘position sensors’. These refer to any device that is capable of measuring the position of something in relation to its fixed or relative position. And if you are interested in knowing more about position sensors, then the brief outlook below will definitely help you.
Types Of Position Sensors
There are numerous types of positions sensors available in the market. Four of the most common ones include – potentiometers, magnetic, optical, and Inductive. Potentiometers are the most often used position sensors which measure the drop in voltage in terms of electrical contacts. They are very cheap and lightweight, yet can quickly damage themselves due to excessive wear and tear. Magnetic sensors, as the name suggests, uses a magnet to measure position changes. These are robust position sensors but are prone to malfunction if subjected to extreme shock. In addition, they might also not perform too well in conditions of high temperatures.
Optical sensors, also known as encoders, work by using a beam of light to generate a position signal. While on the plus side these sensors have very high resolution and accuracy, their weakness lies in the fact that they can fail at any time without any warning. Finally, inductive sensors are known to be very reliable no matter how harsh the environment is. Many position sensor manufacturers like Positek manufacture inductive sensors which are known to be reliable and highly accurate in their readings. Most industries dealing with applications related to safety almost always use inductive position sensors as their senor of choice.
Resolution VS Accuracy
A position sensor resolution refers to the change in position while its accuracy refers to the veracity of its measurements. Both these are not same even though some manufacturers try to project it as being the same. Even if a sensor produces one million counts, you should not confuse it as being accurate every single time. What is a more important criterion is the sensor’s repeatability, or how often can the sensor provide accurate results.
Many people are obsessed with using the least costly position sensor in their projects. This mostly happens because of their mistaken concept of cost. The cost of a sensor is not only its purchase price but also the cost you incur as a result of its failure. A cheap position sensor might save you money initially. But if the sensor fails, the cost you will have to incur as a result of failure will be far greater than the money you saved by buying a cheap sensor. So, instead of blindly looking at just the cost of the sensor, buy a position sensor by ensuring that it will never fail.
Environment And Sensor Type
All position sensors cannot be used in all types of environments. While some may perform well in fluctuating temperatures, others might fail in that exact environment. As such, make sure that you know which type of sensor is suitable for which environment. For example, if the environment involves an extended period of vibration and shock, then stay away from using potentiometers. Similarly, in conditions which are wet and dirty, avoid using capacitive or optical sensors. And if the environment has highly fluctuating temperatures, then using a magnetic or optical sensor is a strict no-no.
Be sure to check the specification of the sensor fully before buying it. Since the industry is not too well regulated, some manufacturer might only publicize a few information like resolution while completely avoiding to mention other important data like accuracy and repeatability. Such details might only be available in the specification datasheet. And only by reading through them will you get a true picture as to whether a senor meets your requirements or not.
Some engineers often make the mistake of inferring a component’s position by comparing it with another component’s position. This is bad practice and something that you should never do. The position of a component must always be noted by measuring it directly, not through inference. If you rely on inferred measurements too much, then the performance of the device can deteriorate, even putting its reliability to question.
Position sensors can fail from time to time. And one of the major causes of such failure is failing to properly account for cables and connectors. Special attention should be given to ensure that the cables are not strained in any way, especially in an application that will experience vibration or shock for long periods of time.