How Tachometers And Encoders Are Different?

When talking about tachometers and encoders, these control systems mainly differ on the feedback that each one of them gives. Though both ensure reliable, smooth and accurate operation, but a little confusion between these terms often leads to over-design or over-engineering because it is possible for tachometers to perform a basic function as encoders. And, the best part is a simple tachometer can do the job of a wide range of complex encoders. So what sets them apart when they can perform same? Well, actually both encoders and tachometers are designed to provide you information about the movement of a motor shaft. The only difference that makes them different is that a tachometer is used to measure a speed while encoders are used to calculate the position.

In order to understand them in a better way, let’s discuss both the devices one by one:

Coming over to Tachometers first, it is the device that is designed to calculate the rpm of a motor. One can achieve this in a number of ways and Hall Effect is one of them. This can be used to measure every time the motor makes a full revolution. There are also other mechanical methods available as well to take these measurements. The only plus point of using mechanical tachometers is that they are simple, easy to use and require only one measurement per rotation. They are backed by extensive digital technology and electronic systems that record high-speed rotations and show the readings in a recordable plus digitized format. A simple model of a tachometer comprises a dial, timer, and a needle, which combine together to calculate the number of rotations per minute or hour. However, it is their simplicity that makes them a viable option.

Let’s talk about Encoders now, although tachometers and encoders are same in functionality but encoders aim for a much higher resolution as compared to tachometers and are more complicated to use. They help tell you the position of the motor shaft and are available in two main types. There are single turn encoders and multiturn encoders. Here, we will be discussing the single turn ones, which are further classified into two types: Incremental Encoders and Absolute Encoders.

• Incremental Encoders: These are simpler of the two types and provide a reading every time a motor shaft rotates a certain distance.  
• Absolute Encoders: Well, these encoders will provide you an exact position of the motor shaft. They make use of the most common measurement types, optical and magnetic based readings, where the processor calculates the exact position of the motor shaft and provides you highly accurate results. Unlike Incremental encoders, you don’t need a starting algorithm here and the position can be immediately calculated without the need for any movement.

However, using an encoder as a tachometer will definitely offer you the benefit of improved dynamic response, where you don’t need to wait for full rotation to update your measurement and lets you measure the speed of a motor with greater accuracy.

So, in this way, both tachometers and encoders are same as well as different.