Control device for regulating the pressure of a fluid
A control device for controlling the pressure of a fluid, and a porometer that includes the control device. A regulating unit includes a pipe system for conveying a fluid and a regulating device associated with the pipe system. The regulating unit includes a first pressure regulator and a second pressure regulator, and the first and second pressure regulators each generate a regulating variable for an actuator for configuring the flow of the fluid in the pipe system; and a controller. The first pressure regulator is arranged on the inlet side in the pipe system. The second pressure regulator is arranged in series downstream of the first pressure regulator with respect to the direction of flow of the fluid in the pipe system. The controller is configured to specify a pressure setpoint value as a reference variable for the first pressure regulator and the second pressure regulator.
1 . A porometer, comprising:
a device for holding a sample to be measured; and
a control device for controlling a pressure of a fluid, which is arranged upstream of the sample to be measured and pressurizes the sample to be measured with a fluid under defined pressure conditions, wherein the control device comprises:
a pipe system for conveying a fluid, the pipe system having an inlet and an outlet and the fluid flowing in the pipe system from the inlet to the outlet,
a regulating unit associated with the pipe system, which comprises:
at least two pressure regulators, which comprise a first pressure regulator and a second pressure regulator, the first and second pressure regulators each generating a regulating variable for an actuator to configure the flow of the fluid in the pipe system, and
a controller, wherein
the first pressure regulator is arranged on an inlet side of the pipe system,
the second pressure regulator is arranged in series downstream of the first pressure regulator with respect to a direction of flow of the fluid in the pipe system, and
the controller is configured to specify a respective pressure setpoint value as a reference variable for the first pressure regulator and the second pressure regulator.
2 . The porometer according to claim 1 , wherein the pipe system forms a compensation volume in a region between the first pressure regulator and the second pressure regulator.
3 . The porometer according to claim 2 , wherein the volume of the compensation volume is greater than a volume of a pipe of the pipe system that extends between the first pressure regulator and the second pressure regulator.
4 . The porometer according to claim 2 , wherein the pipe system forms a further compensation volume downstream of the second pressure regulator.
5 . The porometer according to claim 4 , wherein the volume of the further compensation volume is greater than the volume of a pipe that extends between the second pressure regulator and the outlet of the pipe system.
6 . The porometer according to claim 1 , wherein the pipe system runs linearly without forming branches.
7 . The porometer according claim 1 , wherein the pipe system forms two parallel pipe paths between the inlet and the outlet, wherein
the at least two pressure regulators comprise the first pressure regulator, the second pressure regulator and a third pressure regulator,
the first pressure regulator is arranged on the inlet side of the pipe system before the pipe system branches into two parallel pipe paths, namely, a first pipe path and a second pipe path,
the second pressure regulator is arranged along the first pipe path, and
the third pressure regulator is arranged along the second pipe path.
8 . The porometer according to claim 7 , wherein one of the first and second pipe paths forms a high-pressure region of the control device, through which the fluid flows when the pressure is above a threshold pressure, and the other of the first and second pipe paths forms a low-pressure region, through which the fluid flows when the pressure is below the threshold pressure.
9 . The porometer according to claim 8 , wherein the pipe system comprises protection valves controllable by the controller, wherein the pipe path for the high-pressure region or the pipe path for the low-pressure region is activated by controlling the protection valves.
10 . The porometer according to claim 1 , wherein the regulating unit further comprises an inlet pressure sensor at a beginning of the pipe system, which measures an actual pressure value on the inlet side and feeds the actual pressure value to the controller.
11 . The porometer according to claim 1 , wherein the regulating unit further comprises an outlet pressure sensor at the outlet of the pipe system, which measures an actual pressure value at the outlet of the pipe system as a controlled variable, the controller detecting the actual pressure value measured by the outlet pressure sensor.
12 . The porometer according to claim 1 , wherein the first pressure regulator is configured to carry out a pre-regulation of the pressure in the pipe system, the first pressure regulator receiving a first pressure setpoint value from the controller.
13 . The porometer according to claim 12 , wherein the second pressure regulator is configured to carry out a fine regulation of the pressure in the pipe system, the second pressure regulator receiving a second pressure setpoint value from the controller.
14 . The porometer according to claim 1 , wherein the first and second pressure regulators are configured as PI or PID regulators, one of the first and second pressure regulators being configured in such a way that the I component of the regulation in that pressure regulator that is so configured is switched off or reduced, and the controller interacts with that pressure regulator in such a way that the I component of the regulation is carried out by the controller.
15 . The porometer according to claim 1 , wherein the first and second pressure regulators are configured as PI, PD or PID regulators, wherein one of the first and second pressure regulators is configured such that the P component and/or the D component of the regulation in that pressure regulator that is so configured is switched off or reduced, and the controller interacts with that pressure regulator such that the P com ponent and/or D component of the regulation is carried out by the controller.
16 . The porometer according to claim 1 , wherein in an operating state in which the control device applies a pressure to the sample to be measured in such a way that the sample in any case is partially flowed through by the fluid, the controller is configured such that:
the first and second pressure regulators are controlled via the controller in such a way that valves obtained in the first and second pressure regulators for the configuration of the flow of the fluid in the pipe system are opened to such an extent that the flow through the first and second pressure regulators is equal to the flow through the sample through which the fluid flows.
17 . The porometer according to claim 1 , wherein in an operating state in which the control device applies a pressure to the sample to be measured in such a way that the fluid flows at least partially through the sample, the controller is configured in such a way that:
the first and second pressure regulators are controlled via the controller in such a way that valves obtained in the first and second pressure regulators for the configuration of the flow of the fluid in the pipe system are opened to such an extent that the flow through the first and second pressure regulators deviates from the flow through the sample through which the fluid flows on average at most to such an extent that a change in pressure close to the sample does not exceed a predefined level.