8270A/8370A
Operators Manual
16
When controlling down in pressure, the Product will exhaust
gas through the EXHAUST port. The flow of this gas can be
greater than what the vacuum pump can support. When
working at higher pressures, Fluke Calibration recommends
that the vacuum pump be turned off and equipped with an
auto-vent valve.
TEST Port
Pressure instruments and devices to be tested are connected to the TEST port.
Tubing connected from the Test port to the load volume should have an internal
diameter >2 millimeter (0.083 inch). For optimal performance, tubing should be
<5 meters (15 feet) when minimum diameter tubing is used.
To prevent oils, grease, solvents, and water that could be present in a Device
Under Test (DUT) from contaminating the Product, a Contamination Prevention
System (CPS) is available for use with the Product. The CPS sits on the bench
and provides a platform to test pressure instruments and devices. The CPS
connects directly to the TEST port. For more information, see the
CPS-40M-
HC40/CPS-100M Instructions
.
Note
Excessive leaks in the test volume affect control stability and can
cause measurement errors in the DUT.
W
Caution
To prevent damage to the Product, when the Product is
connected to a system with liquid contaminants, take proper
precautions to purge the system and test line. Not doing so can
cause Product contamination and result in a need for non-
warranty service.
Note
Minimize the length of the test connection tubing to enhance control
performance and reduce pressure setting time.
The Product pressure control will not operate properly if there are
excessive leaks in the test system. The maximum acceptable leak
rate for optimal automated pressure control operation and to ensure
in tolerance measurements with default pressure control parameters
is
0.5 % of set pressure/minute. In DYNAMIC CONTROL modes
(Dynamic A and Dynamic B), to handle higher test system leak
rates, use Control Settings to increase the ready tolerance.
REF Port
The REF port (Reference port) is open to atmosphere for gauge measurements
or it can be connected to the reference port of the pressure instruments and
DUTs.
Instruments with a low full-scale pressure range require special handling to
assure their performance. These instruments are sensitive to atmospheric
pressure changes, including disturbances in the atmospheric pressure. The
reference side must be carefully controlled or changes due to wind, air handlers,
doors shutting, and more will cause major variations in the readings. The Product
tracks these changes but it may not track in the same way as the DUT. To
control these changes, Fluke Calibration recommends that the reference port
(also referred to as the "test-(test minus)" or "low" port of all relevant DUTs be
tied to the REF port of the Product.
