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When paying out media from a spool, hold back tension is required. The CTPS (Constant Tension Payoff System) provides this tension, regardless of the spool diameter or media speed. The media may be just about anything (i.e. wire, fiber optic cable, cloth, etc.). The tension is provided by a frictionless magnetic brake which delivers precision and repeatable resistive torque. The controller is designed to be user-friendly and allows the operator to see both the set tension (controlled by a knob) and the measured tension.

The CTPS was designed to economically replace existing payoff systems that do not provide a constant tension upon a changing spool diameter or systems that perform poorly overall.

MBS offers two types of systems; both consist of a brake mounted on a cradle, a controller, and a spool measuring device.


This CTPS system utilizes a laser to measure the diameter of a spool. Knowing the spool diameter, the controller can provide the set tension (within a few percent) prior to feeding media and/or using feedback.


This CTPS system utilizes a metering roller to measure the linear speed of the media. By comparing the linear speed to the spool speed, the controller may calculate the spool diameter. This is an optimal system when working in an environment where a laser cannot be used.

The tension may be set using the potentiometer on the front of the controller or through the remote cable supplied with the system. The tension is provided by an MBS frictionless magnetic brake. The brake torque is produced by a magnetic field, and thus, with no friction, there is no wear, no dust being generated and virtually no maintenance. The microprocessor, located in the controller, controls the brake tension based on the following inputs: the set tension, brake speed, and spool diameter and/or the speed of the media. The brake is coupled to a payoff spool through a belt and pulleys. A load cell measures the torque of the brake. The user may define if the system operates in an open or closed loop.

Magnetic Brake Systems (MBS) CTPS System


The controller provided with the CTPS offers two tension control modes:

  1. Manual mode, where the operator may control the system directly from the controller. 

  2. Remote mode, where the system may be controlled by a computer or remote 0-10 VDC signal.


The spool speed is measured by the brakes' encoder. The transmission information is factory set but may also be changed in the field.

The controller uses one of two methods to determine the spool diameter:

  1. Laser: the initial set-up requires two steps: mounting the laser and aiming it towards the center-line of the spool. 

  2. Metering Roller: the controller compares the spool speed to the media speed. The media speed may be measured by:

  • Using an existing idler roller in the system, equipped with an encoder.

  • Adding a roller with an encoder.

  • Adding magnets and a hall effect sensor to an existing roller.

From the set tension and calculated spool diameter, the controller calculates what the resistive torque should be.


The resistive torque is provided by a frictionless magnetic brake. The brakes are manufactured by MBS and the size is determined by the continuous power dissipation required; performance curves may be found in the section, Magnetic Brakes. The transmission is based on the torque requirements of the payoff spools.


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