The Schneider Electric SRD998 is a position controller for pneumtic control valves. Pneumatic control valves use spring action to close the valve if no air is supplied.
The SRD998 supplies air and reads the position of the valve piston, building a closed loop control positioning the control valve.
File:SE SRD998 TypicalMounting.png
NOTE: The metal bar (A) in this picture is not the actuator, it provides the position feedback. Do not try to move the valve with this bar.
1 Hardware Connection[edit | edit source]
Electrically the only connection needed is the setpoint signal 4-20mA (translates to 0-100% position setpoint).
This signal also provides the neccessary power supply for the electronics.
The movement itself is done by air supply. Basically the SRD acts as a proportional valve with feedback loop.
The 4-20mA setpoint signal is connected to terminals 11(+) and 12 (-).
2 Commissioning[edit | edit source]
File:SE SRD998 TestProcedure.png
For each valve the tuning and optimizing procedure must be done.
The complete instruction manual is attached in the info-box.
1. Open the cover to access the rotary selector knob.
2. Check if you have compressed air supply.
3. Press the selector knob once to access the menu.
4. Rotate the selector knob to navigate through the sub menues.
5. A normal two way valve with the mounting setup as shown in above picture needs MOUNTING > STROKE RIGHT
Menu Mounting depends on the mounting situation.
Our test unit needs to be Stroke Right and Valve Action Direct (default).
Select by pressing the selector know once.
You can adapt to different mounting situations with this menu.
File:SE SRD998 menuMontingConfig.png
6. Perform the tuning and self optimization procedure by selecting AUTOSTART > SMOOTH RESPONSE
The SRD998 will first find the valve's limits and move the piston all the way up and down.
Then it will start to measure movement and speed and begin with small position changes while determining it'S PID parameters.
The whole procedure takes about 2 minutes.
