This signal type cuts the amplitude of the wave and the actuator recognizes this signal as a proportional movement. MFT provides the ability to program characteristics of the actuator.
Some of the key characteristics to change are:. Belimo actuators are compatible with many control inputs and all direct digital control DDC systems. For ease of understanding, our example will be a heating application.
The set point the desired control point in this case is 68 degrees with a temperature differential of 2 degrees for the controller.
When the controller receives a signal from the sensor that the set point has been achieved, the controller then sends a signal to the valve to position to fully closed. The actuator starts to slowly drive open the hot water valve, increasing the heat in the controlled medium. When set point is reached the actuator stops opening the final control device hot water valve and tries to hold at set point.
If set point starts to be over-shot, the controller sends a signal to the actuator to start to drive close the valve. Review: Set point control is achieved when the sensor signal from the controlled medium starts to deviate from the controller set point. The controller sends a signal to the actuator of the final control device valve or damper to slowly drive open. As the set point is approached the controller sends a signal to the actuator, then the actuator stops and tries to maintain set point.
If set point is passed the controller sends signal to the actuator to drive the final control device to a closed position. Proportional means that the size of the output is related to the size of the error detected by the controller.
The controller calculates how much the final control device needs to open without over-shoot and will start reversing the actuator to close the final control device to a percentage of the closed position to maintain set point. Popular modulating control signals include ma and volts.
If you were to look into a control panel like a Hoffman Enclosure you might see controls like a Honeywell UDC that could be taking a ma signal from a device like a Hawkeye current transmitter and based on the control input signal from the Hawkeye which would most likely be a ma signal the UDC controller would respond with a ma output signal to a device like a Honeywell Variable Frequency Drive which would control either a fan or a pump. This is an example of how a proportional signal like a ma signal is used in modern HVAC controls.
Make sure to check out this video on 2 and 3 way valves! The digital output DO must stay energized or de-energized to maintain the actuator in its desired state. Modulating control provides a higher degree of positioning control.
Popular modulating control signals include mA and V. IAI provides actuators for both the commercial and industrial sectors. Email: Sales iVact. Note that is not the same as minimum outdoor air Flow! Another is where two actuators need to be sequenced, one before the other. It is also easy for the service man to use a meter at the actuator and see the position signal from the controller. It may require a computer connected to the controller to know the actuator position signal in floating applications.
Either actuator should be easy to test by a trained service person. When a proportional actuator is restored to service, the proportional actuator will return to the position the controller is outputting. The floating actuator's controller will need some input to restore operation. Usually the setpoint can be kicked or the controller reset with no problems. So floating actuators tend to be applied in positions where simple control is needed. Especially where there are multiple units like terminal units where the cost advantages add up.
So floating actuators have the image of being low quality because they cost less and are used on simple stuff. Actual quality depends on how they are built and applied. Please read this Valves, Regulators, Filters, Etc.
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