Many actuators are compatible with many control inputs and all Direct Digital Control (DDC) systems. There are many signals to select from with today’s controllers. What does ‘on/off’, ‘open-close’, ‘3-point’, ‘tri-state’, ‘floating point’, ‘proportional modulation’, ‘phase cut’, ‘PWM’ or ‘MFT’ mean? Let us help you quickly understand more on this control signal jargon.
On/Off or Open-Close: The actuator is able to drive either to its full open position, or to its full closed position. The same indication is used for spring return type actuators. Where the actuator will drive to its full open position and spring return to its zero position. This can also be reversed.
3-point, Tri-State, Floating Point: The actuator has both clockwise (CW) and counter-clockwise (CCW) control inputs. One drives the actuator to its open, the other to its close position. If there is no signal (Null point) on either input the actuator simply stays in its last position.
Proportional Control: The actuator drives proportional to its control input and modulates throughout its angle of rotation. This control type is usually a variation of VDC. Common values are: 0-10 VDC 2-10 VDC, It is common to also have a 0-20 or 4-20 mA output from a controller. This can be very easily converted to 0-10 VDC or 2-10 VDC with a 500 W resistor.
Pulse Width Modulation (PWM): The actuator drives to a specified position according to a pulse duration, the “length” of signal. The pulse can originate from a dry contact closure or a triac sink or source controller. An example of PWM control:
- Time base: 0 to 10 seconds
- Output pulse: 5 seconds
- Actuator position: 50%
Phasecut: An actuator drives depending on the power result of a remaining wave. This signal type cuts the amplitude of the wave and the actuator recognizes this signal as a proportional movement.
Multi-Functional Technology (MFT): This technology is only available by Belimo. It allows you to create custom solutions for individual applications using the same programmable actuator. Whether you need a particular control or feedback signal, or need to change running speeds, MFT is the answer. It comes standard as a 2 to 10 VDC proportional control but can be reprogrammed on-site. Some of the key characteristics to change are:
- Control Input – selectable On/Off, VDC, PWM or Floating point
- Motion values – selectable Running time adjustment
- Feedback – selectable feedback values
MFT makes it easy to set parameters for running time, mechanical working range, address, status and diagnostics. Learn more about MFT at www.belimo.us. Or download the MFT technical guide.