Fluke RUSKA 7252, User Manual

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Installation
Pneumatic Connections
3
3-5
control valves will cause some temperature variations. Thus the appropriate setting varies
but a good compromise can be found. To observe the variations, connect the reference as
discussed and open the test port to the atmosphere. In measure mode, the Calibrator will
indicate the variations. A good filter may be usable in place of the valve if it provides
approximately the correct restriction of air flow.
One consideration is that if the reference port is completely sealed from atmosphere, its
pressure will change due to barometric pressure changes or temperature changes in the
environment. If the pressure in the reference port becomes lower than the barometric
pressure, then a vacuum pump would need to be attached to the exhaust port to allow the
controller to control down close to 0 psig.
For permanently absolute systems, a vacuum pump capable of producing a vacuum level
of 200 mTorr or less at the sensor reference port is required (used to zero the sensor).
See Appendix A for vacuum pump requirements. (See also Chapter 3, Absolute Mode
Requirements section).
For instruments that have a barometric reference sensor option, the barometer is tied to
the reference port. When operating in the gauge mode, the reference port should be
connected as noted above. When operating in the absolute mode, sealing the reference
port from atmosphere will improve the stability of the Calibrator.
glb09.bmp
Figure 3-1. RUSKA 7252 Back Panel
Vacuum Sensor Option
The Calibrator is also available with a vacuum sensor option. On a permanent absolute
instrument, this sensor is used to zero the RUSKA quartz sensor at a high vacuum.
On a Calibrator that has the Evacuated Reference Option, this vacuum sensor is used to
monitor the vacuum level in the reference port when the reference port is pulled to a hard
vacuum allowing the Calibrator to operate in the absolute mode.