How to Install an Industrial Rotary Encoder: Mounting, Couplings & Wiring Guide
Installing an industrial rotary encoder correctly is the difference between years of reliable feedback and a string of noisy signals, worn bearings and unexplained drive faults. This guide is written for maintenance engineers, electricians, OEM machine builders and anyone replacing a motor feedback device, such as an old DC tacho generator, on plant equipment. It covers how to choose a mounting location, mount solid and hollow shaft encoders with brackets, flange adapters, torque arms and couplings, and route the cable so it’s protected. If you’re working with a small panel-mount encoder for an Arduino or electronics project, this isn’t the article for you. Our focus is heavy-duty encoders on motors, gearboxes and machinery.
Need help finding a replacement encoder? Send any questions through our contact page here, or call us directly on 1300 236 467
Choosing the Right Mounting Location
The questions you should be asking yourself are:
Before or After the Gearbox?
Am I going to get accurate measurement results at this location? Consider vibration, slip, speed limitations etc.
Protecting the encoder from vibration, heat and impact
Is the encoder protected from the being knocked or bumped because it is protruding out? Is it exposed to the elements or rain. Is it exposed to high temperature such as mounting directly onto the back of a motor. Not considering these protection factors can not only affect the longevity of this sensitive device but also may affect the accuracy mentioned above.
Solid Shaft vs Hollow Shaft Encoders: Which Should You Use?
Blind hollow shaft vs through hollow shaft?
There are multiple choices of encoder mechanical design.. For example solid shaft or hollow shaft.. Where you buy your encoder from is important to be sure all the most suited options are available.
Choose the shaft type; solid or hollow.
Note: Modern programmable or magnetic encoders do not always allow for a hollow shaft to go all the way through, due to the electronics used.
These blind hollow shaft limit the mounting possibilities, that a traditional through hollow shaft encoder might have (usually on optical encoders).
Servo flange vs clamping flange
Choose the flange type; Flange, Clamp
The following Accessories are available from PCA Encoders:
Rotary Encoder Mounting Brackets
An encoder clamp bracket allows you to mount a rotary encoder securely to a flat surface.
The clamp diameter is available in sizes that supports mounting all the standard encoder body diameters, such as 58mm, 70mm, and 90mm.
Rotary Encoder Flange Adapters
These are used to convert one type of mounting to another, allowing you to use a rotaru encoder that does not come natively from the manufacturer with your flange requirements, or simply to utilise a more readily available encoder.
Example 1: Old tacho generators often used on DC motors on years gone by, used the REO flange design.
With the AF90-REO adapter, this allows a standard modern 90mm body encoder to have the mountings of a REO Flange
The clamp is tightened around the encoder body with a clamp bolt.
Torsion Arms for Hollow Shaft Encoders
Do hollow shaft encoders need a torque arm?
When a hollow shaft encoder mounts onto the rear shaft of a motor for example, it is not required to be bolted onto the motor frame. It in fact can be allowed to move freely on the back of the motor, this does not affect the accuracy of readings. However to prevent it from rotating endlessly and the cable wrapping around the shaft, a torsion arm can be used to hold it in place.
The torsion arm bar has length adjustments to ensure that the encoder is held straight.
Rotary Encoder Couplings
When joining two solid shafts (one on the application the other on the encoder sensor), shaft couplings can help with a few things:
Your coupling may also serve as a reducer, a good encoder supplier will stock a many combinations shaft sizes on either end of the couplings.
A coupling is usually designed to be flexible and mitigate backlash. Backlash can cause instability in a precision motion control application. Simply put, this is “play”, like you might notice in your car a steering wheel. You notice it most as rest and when you change direction, there is a delay in response.
Oldham Coulings
An Oldham design coupling uses a tongue and groove designed plastic wedged between the two end clamps.
Spring and bellows couplings
Other flexible coupling can also achieve this with a type of spring or bellows integrated into the design.
Other things to remember:
When you are mounting a absolute encoder: lets assume it is a single-turn absolute encoder with a 4~20mA output.
A single turn with 0-360° rotation = 4-20mA output. The terminals on the encoder will have a Zero pin digital input signal, which when a positive voltage is applied, will allow you to set the Home or Zero position (4mA output). This is done once you have completed mounting the encoder.
Cable & connector considerations:
The selection of a radial (side) or axial (rear, inline with the shaft axis) cable / connector exit position, are important to ensure that the cable or connector is not protruding into an area where it may be knocked or bumped causing damage.
A tangential cable exit design is a combination of both axial and radial. This allows the encoder to be used in installations where you are replacing an encoder either with a radial or axial exit position.
For further advice on mounting rotary encoders please contact PCA Encoders.
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