What is a Modulating Actuator?

An electric actuator is the mother device of valve automation. It transforms electrically produced low-speed rotary motor torque into high-speed rotary torque. There is an internal system for modulating electric actuators. It helps to position the output shaft in response to an input control signal. Modulating actuators don’t need to travel the whole span from open to closed in one movement, and it’s not like on-off electric actuators. These actuators move only according to the change of the input control signal. The input signal fixes the proportional positioning. For 0-10V, 0V is closed, and 10V is open. 5V is 50% open.

The positioner continuously observes and compares the input control signal proportionately to the physical location of the output drive. If an exception is found, the positioner fixes the direction and run time of the actuator motor to withdraw the exception.

The standard analog control input signal is 0-10VDC, and the common current rating is 4 to 20mA. A few modulating electric actuators provide an output signal. Here, the attained position is compared to the wanted position.

A modulating control valve is an automated valve. It is used to control the amount of flow in a system. There are actuators on these valves that use feedback and control signals. Actuators help to open and close the valve accurately. A control signal is sent to the actuator to train it on how far to raise or turn the medium. The control signal is in the form of air pressure or electrical voltage. For example, a 3 to 15 psi pneumatic signal causes the actuator to close the valve at three psi or lower fully. Again, a 3 to 15 psi pneumatic signal occurs for the actuator to open it at 15 psi or above. A 0 to 10-voltage DC electric signal causes the actuator to close the valve completely at 0 voltage DC. Similarly, completely open it at ten voltage DC or above.

Usually, a flow meter downstream from the valve is used. It measures the flow rate and sends that data to a control computer. The computer then applies the proper logic, which can generate the signal. The signal adjusts the valve in either direction until the desired flow rate is met.

Pros & Cons of Modulating Actuator

• Precision: An actuator can precisely control the flow by adjusting the flow passing through the valve. This amount may change depending on the application’s requirements.
• Efficiency: The actuator consumes less energy than frequent on/off action.
• Remote Control: Modulating Actuator provides remote and automated control facilities.
• The actuator generates heat and requires frequent & scheduled maintenance.
• Time-consuming related to a hydraulic or pneumatic actuator.

From Jumper man Tech

Uses of Modulating Actuators with 0 to 10 Volt

• HVAC systems
• Power plants
• Steam supply lines
• Wastewater treatment plants
• Automation industry
• Irrigation systems

Technical Data Specifications of an Ideal Modulating Actuator

 Modulating Actuator Function 

We can monitor the physical position of the modulating electric actuator’s output shaft in two different ways. One is using a mechanical device, a potentiometer, which is run by a gear connected to the output shaft. Another way is sensing the shaft position digitally. In past years, the mechanical potentiometer system was the only choice. Even this system is performing well. We should also count the potentiometer failure in this system.

Digital magnetic position sensing is an excellent invention for determining the output shaft position. It happens with Hall-effect sensors. A magnet is set to the modulating actuator’s output shaft, and a digital encoder is also used. This process is very precise and digital.