Calculating Output Frequency for Rotary Encoders

March 10, 2013

Here are three handy calculations for incremental rotary encoders:

Frequency = (RPM X Line Count/60)

Use this formula when line count of the encoder and RPM are known. The answer is in Hertz (Hz) or cycles per second. Keep in mind that many encoders and drives will have a maximum frequency limit that you should not exceed.

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Line Count = (Frequency X 60/RPM)

Use this calculation when Frequency and RPM are known. Can be useful for determining the highest resolution incremental encoder you can use without over driving the maximum output specifications on the encoder or equipment it is being connected to.

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RPM = (Frequency X 60/Line Count)

Use this formula when frequency and line count are known. This is useful when you are trying to determine the speed of rotation.

Use our free online encoder calculator

Quantum Devices Inc. provides an online encoder calculator for finding RPM, encoder output frequency or line count (resolution) when given the other two variables.

You might find our encoder calculator useful under the following circumstances:

Solving for Resolution:

When trying to determine the line count of an unknown encoder if you spin the encoder at a given RPM, then use an oscilloscope and find the output frequency, you can find out the resolution of an unknown encoder.

Solving for Frequency:

If you know the RPM and line count of your optical encoder you can calculate the output frequency. This is a useful check when you are designing in an encoder to make sure you do not overrun a the input frequency limit of a drive, controller, or other device.

Solving for RPM:

This is often used to validate the actual speed at which a machine or motor is running.

Quantum Devices is a manufacturer of rotary encoders.  Incorporating QDI’s patented sensor technology, our QPhase^TM Family of Encoders feature high resolution, increased frequency response and superior reliability over temperature (0 to 120 degrees C). QDI incremental and absolute encoders set a new standard and are backed by a 2-year factory warranty. You can buy rotary encoders online direct from our store. We invite you to request an evaluation unit, additional information or price quotations.

Contact Quantum Devices online for help choosing the right encoder for your application.

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