DH Instruments PPC3 - Connecting to the Device under Test (Test(+) and Test(-) Ports)

PPC3™ OPERATION AND MAINTENANCE MANUAL
© 2002-2007 DH Instruments, a Fluke Company Page 10
For PPC3 to identify external RPM4s, the RPM4 COM1 port settings must be:
Baud rate: between 1200 and 19200
Parity: Even
Date bits: 7
Stop bits: 1
If PPC3 is not able to establish communications with RPM4s and their Q-RPTs, check
that the RPM4 COM1 port setting conform to the requirements above. If the COM1 port
settings are correct, check that the correct communications cable is being used
(standard pin-to-pin DB-9M to DB-9F RS232) and is connected to the correct
communications ports.
PPC3 COM2 > 1
st
RPM4 COM1; 1
st
RPM4 COM2 > 2
nd
RPM4 COM1
See the RPM4 Operation and Maintenance Manual for additional information on RPM4
RS232 communications and COM port settings.
2.3.8 CONNECTING TO THE DEVICE UNDER TEST (TEST(+)
AND TEST(-) PORTS)
If you are using a self purging liquid trap (SPLT), see Section 2.3.8.1 before proceeding to
connect the device under test.
If the PPC3 has a G15K or BG15K Q-RPT, a dual volume unit (DVU) should be installed for
very low pressure control. See Section 2.3.8.2 before proceeding to connect to the device
under test.
Using a pressure connecting hose or tube of appropriate pressure rating, connect the device or
system to be tested to the PPC3 TEST(+) port. The PPC3 TEST(+) connection is 1/8 in. NPT female.
PPC3 TEST(+) AND TEST(-) PORTS
All PPC3s have a TEST(+) and a TEST(-) port. See Figure 13 for PPC3 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 PPC3s 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 PPC3. For example, if the PPC3 is controlling
pressure into DUTs in an environmental chamber, the pressure in the environmental
chamber may be different from ambient pressure around the PPC3. 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 DUTs, 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 PPC3 TEST(-) port(s) directly to the low or
reference side of the device under test to assure 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.