6 Reference and Specification
K0443 Revision A 6 - 4 [EN] English
6.2 Operational Requirements
Caution
A contaminated UUT must have additional in-line filters connected between the output
port and the UUT to prevent contamination of the instrument.
Negative or Vacuum Supply
The negative supply for absolute control does not need to be regulated. Any variation
between this and absolute zero will affect instrument operation if controlling at low absolute
pressures.
Oil Contamination
Precautions must be taken against oil transfer to the instrument.
Recommended
1. A normally-open venting solenoid connected to atmosphere and the pump. When the
pump supply is switched off, the valve opens allowing atmospheric pressure to enter
the pump directly rather than through the pipe to the instrument.
2. If the above is not done, oil may progressively move up the supply pipe and into the
instrument.
Pump Performance
Recommended for ranges above 2 bar (30 psi) gauge, positive full-scale
1. When installing a vacuum supply protect the vacuum pump against the discharge of
positive pressure by the controller into the vacuum pump. This may result in reducing
vacuum pump performance.
2. Use a check valve in the negative supply to vent excess pressure to atmosphere if the
vacuum pressure rises above atmospheric pressure. The check valve should be
installed on the instrument side of a volume which is approximately equal to the
system volume. The volume slows any rapid pressure rise giving the vacuum pump
time to reduce the pressure.
Note: A wide bore vacuum pipe can have enough volume and, used with a check valve,
could provide the necessary overpressure protection.
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