19 / 62
5 • Circuit Descriptions
80116-276_V24169
2022-01
Description of the various assemblies
Pneumatic system
The argon gas is extracted from the gas cylinder at approx. 200 bar. Down-
stream of the pressure reducer unit it is available at the APC unit with ap-
prox. 5 bar. The pressure reducer unit is equipped with a high-pressure
sensor which can be used to identify the level of gas in the cylinder.
In the unit itself the internal supply pressure sensor is downstream of the
input filter. A switching valve is then used to switch the gas to the control
unit. This consists of the internal pressure reducer, which reduces the
pressure to 2.5 bar, a proportional valve and the flow sensors. For redun
-
dancy reasons the flow is measured using two sensors based on different
physical principles. One is designed as a differential pressure sensor which
measures the differential pressure occurring at a specified bottleneck.
With the calorimetric flow sensor an electrically heated element is cooled
by the gas flow. This cooling can be used to calculate the flow rate.
The output is also equipped with another pressure sensor which is used to
control the pressure in the instrument. This allows a blockage to be detect
-
ed and the gas pressure maintained at non-critical levels.
APC controller (open and closed-loop control)
A switched mode power supply unit housed on the "APC controller" gen-
erates the necessary supply currents of +5 V, +15 V and –15 V from the
+24 V input voltage.
The processor controls the valves and also the flow according to the val-
ues measured by the sensors.
The control voltage of the switching valves is reduced as soon as they have
been energized. This prevents the excitation coil from overheating when
switched on for lengthy periods.
The "APC controller" receives its specified values from the control panel via
the Erbe Communication Bus (ECB). The parameters for gas control are
thus transmitted and the commands for switch-on and off issued before
every activation.
If a button is pressed on the APC 2, the "APC controller" signals this to the
control panel via the ECB. In return it is informed which LED indicators
must be switched on.
To Next Page
Loading...
Need help?
General
