SMC Networks ITV Series Manual page 28

Working Principle
Power supply
Input signal
q Vacuum pressure
solenoid valve
r Diaphragm
VAC
(Vacuum pump, etc.)
ATM
(Atmospheric pressure)
Series ITV209„
Linearity
0
–20
–40
–60
–80
0 25
Pressure
Characteristics
1.0
Set point Set point
0.5
0
–0.5
–1.0
–100
VAC side pressure (Supply pressure) (kPa)
Downloaded from Elcodis.com electronic components distributor
Pressure
display
Output signal
i Control
circuit
w Atmospheric pressure
OUT.
(Set pressure)
y Atmospheric pressure
Hysteresis
50 75 100
Input signal (% F.S.)
Flow
Characteristics
Set pressure: –20 kPa
–80 –60 –40 –20
When the input signal increases, the vacuum pressure solenoid
valve q turns ON, and the atmospheric pressure solenoid valve
w turns OFF. Because of this, VAC and the pilot chamber e are
connected, the pressure in the pilot chamber e becomes
negative and acts on the top of the diaphragm.
solenoid valve
As a result, the vacuum pressure valve t which is linked to the
diaphragm r opens, VAC and OUT are connected, and the set
Atmospheric
pressure
pressure becomes negative.
This negative pressure feeds back to the control circuit i via the
pressure sensor u. Then, a correct operation works until a
u Pressure sensor
vacuum pressure proportional to the input signal is reached, and
a vacuum pressure is obtained which is always proportional to
e Pilot chamber
the input signal.
t Vacuum pressure
valve
Input
valve
t
+
signal
Control
–
circuit
1
0.5
Return
0
Out
–0.5
–1
0 25 50 75 100
Input signal (% F.S.)
Supply pressure: –100 kPa
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
50 100
l
Flow rate ( /min(ANR))
Working Principle
Block Diagram
VAC.
q
Vacuum
pressure
solenoid valve
r
Diaphragm
w
Atmospheric
pressure
solenoid valve
u Pressure sensor
Repeatability
1.0
0.5
0
–0.5
–1.0
0 2 4
Count
Flow characteristics
measurement conditions
• Exhaust flow rate of the vacuum pump
used for measurement: 500 l /min (ANR)
• Inlet vacuum pressure: –100 kPa
(When outlet flow rate is 0 l /min (ANR))
• Maximum flow rate: 132 l /min (ANR)
(With inlet vacuum pressure at –39 kPa)
150
F.R.L.
AV
AU
AF
AR
IR
VEX
Set
AMR
pressure
Pilot valve
ITV
IC
VBA
VE„
VY1
G
PPA
AL
6 8 10
14-8-31