Page 74 - Instrumentation and Measurement
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FIGURE 5.10 Commonly used direction valves: P or 1 indicates the pressure supply ports, R and S
or 3 and 5 the exhaust ports, A and B or 2 and 4 the signal output ports.
FIGURE 5.11 Examples of valve actuation methods.
As an illustration, Figure 5.12 shows the symbol for a 3/2 valve with solenoid activation and return
by means of a spring. Thus, when the solenoid is not activated by a current through it, the signal port
2 is connected to the exhaust 3 and so is at atmospheric pressure. When the solenoid is activated, the
pressure supply P is connected to the signal port 2 and thus the output is pressurised.
FIGURE 5.12 Symbol for a solenoid-activated valve with return spring.
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