In general, each of these applications requires constantly changing control of flow or pressure, except for leak testing, which typically requires that the set pressure be maintained at all times (and then quickly changed to a new set point for subsequent operation) for testing or new components/packages to be tested).
The constant changes in flow and pressure require that the setpoint change frequently so that the valve operates by constantly changing its opening in response to frequently changing command signals. An example of this situation is a ventilator or anesthesia gas mixing circuit where the flow outputs of two or three valves are constantly adjusted to produce the desired gas mixture. The gas mixture is then delivered to the patient, depending on the design of the device. Other features may include frequent pressure changes in the shockwave therapy device. In order to change the "intensity" of the shock waves produced by the device, the pressure in the system needs to be changed. These dynamic devices require robust CGA valve for medical uses to meet the changing pressure and flow requirements in their respective systems.
3) Types of CGA valve for medical uses
Several methods of operation are used in CGA valve for medical use technology. The most popular valves serving the medical device segment are direct-acting proportional solenoid valves, as they fall within the correct functional range and can serve most medical device applications. However, in some applications, other actuation methods can be used to perform the desired control, including pulse control, pneumatic control and even motor control.
One form of direct-acting CGA valve for medical use is a piezoelectric valve. When a voltage is applied, the valve deforms the piezoelectric element to change the opening of the valve. Like many clinical diagnostic machines, piezoelectric operators can be combined where extremely low power consumption is required (portable devices) or where the application requires extremely low heat generation.
Direct acting proportional coil valves act directly on the piston or slide valve to regulate the valve opening position based on the changing current across the coil. These valves have advantages over pilot valves because they can be applied to a wider range of applications and have simpler construction, fewer mechanical parts, simpler operating principles, and more reliable performance. Direct-acting valves have a longer service life in dynamic operation, where the valve is cycled more frequently. Their robust construction reduces concerns about wearable component failure, and they are generally less sensitive to contamination in air or gaseous media.
Other technical advantages include the ability to reduce overshoot, which is the tendency of a valve to tend toward and then exceed the set point, only to have the valve reverse back to the set point (and possibly exceed it again). This is common in systems that are tuned for fast response times. In a direct-acting proportional coil design, oscillations usually take less time to resolve because the valve moves the piston directly by changing the current flowing to the coil.
Direct-acting proportional coil designs also typically provide precise pressure control. This is critical for applications such as leak testing, which requires very stable pressure throughout the testing phase. The valve is able to respond to small changes in setpoint for tightly controlled pressure regulation.
Overall, the direct acting design has higher speed, responsiveness and resolution, making it superior to air drive or other designs in many applications.
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