2. INSTALLATION
Page 11
© 2009 DH Instruments, a Fluke Company
PPC4 TEST(+) AND TEST(-) PORTS
All PPC4s have a
TEST(+)
and a
TEST(-)
port. See Figure 32 for PPC4 internal Q-RPT
TEST
port configurations.
The
TEST(+)
port is connected to Axxx (absolute) Q-RPTs and to the
high
side of Gxxx or
BGxxx (gauge, bi-directional gauge) Q-RPTs.
The
TEST(-)
port is connected to PPC4s internal barometer, if present, and to the
low
side of
Gxxx or BGxxx (gauge, bi-directional gauge) Q-RPTs.
•
When operating in absolute mode:
The
TEST(-)
port is left open to atmosphere.
•
When operating in gauge or negative gauge mode with a range greater than 50 kPa
(7.5 psi):
The
TEST(-)
port is normally left open to atmosphere. A possible exception is
when the device or system under test is in an ambient pressure that may differ significantly
from the ambient pressure around the PPC4. For example, if the PPC4 is controlling pressure
into UUTs in an environmental chamber, the pressure in the environmental chamber may be
different from ambient pressure around the PPC4. In this case, connecting a tube from the
TEST(-)
port to the inside of the chamber may improve measurement results. If the Q-RPT in
use is an Axxx Q-RPT, this tube must be left open to the environment so that the pressure
inside cannot deviate too far from ambient. When using an Axxx Q-RPT, if this tube is connected
to the low or reference side of UUTs, be sure to open to the local environment as well.
•
When operating in gauge or negative gauge mode with a range less than 50 kPa (7.5 psi):
As a general rule, it is preferable to connect the PPC4
TEST(-)
port(s) directly to the low or
reference side of the device under test to ensure that these are at the same pressure.
When using an Axxx Q-RPT, this connection must also be open to atmosphere. When using
a Gxxx or BGxxx Q-RPT, it is preferable that this connection not be open to atmosphere.
Caution
•
Do not apply pressure to the TEST(+) port without having a pressure
supply equal to or greater than the applied pressure connected to the
SUPPLY port. When controlling pressure to the TEST(+) port
externally, do not cause the pressure to change at a rapid rate. For
example, do not vent suddenly by opening an external valve. Internal
damage to the PPC4 may result.
•
Do not connect a pressure supply to the TEST(-) port. The pressure
applied to this port should be maintained at atmospheric pressure,
between 70 and 110 kPa (10 and 16 psia). Exceeding these limits may
damage a Gxxx or BGxxx Q-RPT and/or the PPC4’s on-board
barometer.
•
Operating the PPC4 connected to a system with liquid contaminants
without taking proper precautions to purge the system and test line
may cause contamination of the PPC4 that will require non-warranty
service.
Note
•
Minimizing the length of the test connection tubing will enhance control
performance and reduce pressure setting time. For normal operation,
the total volume of the device or system under test including
connecting tubing should be less than 1 000 cc (60 in
3
) up to 2 000 kPa
(300 psi) and less than 500 cc (30 in3) above 2 000 kPa (300 psi).
•
PPC4 pressure control will not operate properly if there are excessive
leaks in the test system. In general, the maximum acceptable leak rate
for optimal PPC4 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 mode, to
handle higher test system leak rates, increase the hold limit using
Содержание PPC4
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