Fluke RUSKA 7252, User Manual

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RUSKA 7252
Users Manual
3-4
Test Port
The device(s) under test is connected to the test port. The Calibrator controller is
designed to operate within its specification limits into load volumes from 5 to 60 in
3
(80 to 1000 cc). Excessive leaks in the test volume will cause measurement errors in the
device under test and may possibly affect control stability. Tubing connected from the
test port to the load volume should have an internal diameter greater than 1/8 inches
(3 mm). Tubing should be shorter than 15 feet (5 meters) when minimum diameter tubing
is used.
Single Test Port Operation - Option
Some versions of the RUSKA 7252 allow the instrument to be set-up where the test port
of both controllers are connected together. This can be permanently set at the factory or
on units ordered with this option; a user selectable flag set in [MENU]
Menu | Setup | System | Config allows the system to operate in this mode. With the
test ports connected, the instrument will then allow the operator to control either of the
two channels to a single test port. When set up in this mode, the system software uses an
internal valve to isolate the lower pressure channel from the higher pressure channel
when controlling pressures that are greater than the full scale range of the low pressure
channel. This option is only available with instruments where both channels have a full
scale pressure range that is greater than 10 psi (69 kPa) and less than or equal to
1000 psi (6.9 Mpa).
On systems that are set-up with the test ports connected, the system automatically
switches between the various ranges in the system when in control mode. Because of this,
the main screen is always displayed as a single screen and the full scale of the active
range is indicated in the current unit of measure to the left hand side of the measured
pressure valve.
W
Warning
The software protects the lower pressure sensor from over
pressurization when this mode is activated. If this feature is
turned on, make sure that the test ports are disconnected prior
to turning this feature off.
Reference Port
The reference port is open to atmosphere for gauge measurements or it can be connected
to the Reference Port of the Device Under Test.
Instruments with a low full-scale pressure range require special handling to assure the
performance of the instrument. These instruments are very sensitive to atmospheric
pressure changes including disturbances in the atmospheric pressure. The reference side
must be very carefully controlled or changes due to wind, air handlers, doors shutting, etc.
will cause major variations. The Calibrator tracks these changes but it may not track in
the same way as the device under test. To control these changes, it is recommended that
the reference port of all relevant devices be tied to the reference port of the Calibrator.
The reference port can be sealed from atmosphere in most applications where the test
times are relatively short. This isolates the port from pressure changes in the atmosphere
and results in very stable pressure measurement and control.
If the test times are relatively long, in addition to connecting the reference ports together,
they should also be connected to a tank with a volume of 200 cubic inches or better. The
tank should be vented to atmosphere through a small orifice bleeder valve at the other
end of the tank. The entire reference assembly should be shielded from rapid fluctuations
in air temperature and flow. The vent valve should be set experimentally. In an
environment with no temperature change, it would be closed. In an environment with no
pressure fluctuations it would be wide open. The heat from the Calibrator oven and