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3 Design and principle of oper-
ation
The Type 6134 p/i Converter converts a
pneumatic signal into a standardized electric
signal. It is especially used as an intermedi-
ate element between pneumatic and electric
control and measuring equipment.
The pneumatic input signal from 0.2 to 1 bar
is converted into an electric DC signal from
4 to 20 mA.
Principle of operation (see Fig. 3-2)
A capacitive ceramic pressure sensor (1) is
used to convert the pressure p of the pneu-
matic input signal into an electric DC volt-
age signal. The DC voltage signal which is
proportional to the pressure is amplified to a
defined level in the measuring amplifier (3).
The lower range value and span can be ad-
justed using potentiometers on the front pan-
2
p
P
0,2...1 bar
(3...15 psi)
Fig. 3-2: Schematic diagram of the Type 6134 p/i Converter for two-wire connection
EB 6134 EN
3
1
Design and principle of operation
el. The constant DC voltage source (2) is
used to supply the DC voltage at a constant
level. Control equipment can be connected to
the output circuit.
Output circuit
In two-wire systems, the maximum permissi-
ble load impedance at the output is:
U
= U
B
S
U
Maximum permissible load impedance
B
R
Maximum permissible load
B
U
Supply voltage of the two-wire circuit
S
U
12 V, input voltage requirement (mini-
A
mum connected voltage required)
Example: U
Maximum permissible load impedance at the
output: U
= 20 V – 12 V = 8 V
B
Load: R
= U
B
p
1
2
3
4...20 mA
mA
12...30V DC
– U
R
= U
A
B
= 20 V DC
S
/20 mA = 400 Ω
B
Pneumatic input signal
Capacitive pressure sensor
Constant voltage source
Measuring amplifier and
potentiometers for adjusting
the measuring span (SPAN)
and ZERO
/20 mA
B
3-1
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