Cameron BARTON 753A, User Manual

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14
Section 3 Model 753A Gage Pressure Transmitter
Maximum Loop Resistance
Example 1: (Maximum loop resistance for 10-50 mA system):
V
DC
= 70 Vdc T
VDC
= 12 Vdc
I
DC
= 50 mA R
T
= = 1160 Ohms
0.05
70-12
Example 2: (Maximum loop resistance for 4-20 mA system):
V
DC
= 70 Vdc T
VDC
= 12 Vdc
I
DC
= 20 mA
R
T
= = 2,900 Ohms
0.02
70-12
Example 3: (Calculation to determine maximum loop resistance with
power supply ≥12 Vdc, but ≤ 70 Vdc for 10-50 mA and 4-20 mA systems):
V
DC
= 40 Vdc T
VDC
= 12 Vdc
I
DC
= 50 mA
R
T
= = 560 Ohms
0.05
40-12
I
DC
= 20 mA R
T
= = 1400 Ohms
0.02
40-12
EMI/RFI Shielding
IMPORTANT: The 753A transmitter has no integral electronic interference suppression
features. If an instrument is to be installed in an area containing EMI/RFI
sources and this interference cannot be tolerated, take precautions to
protect the transmitter signal. An optional EMI/RFI filter is available upon
request. Contact the factory for information.
The following precautions are recommended to limit EMI/RFI interference:
1. Run signal wires in solid conduit or use high quality shielded cable to
connect the transmitter to the power equipment.
2. House the transmitter leads in solid conduit up to the junction box where
the shielded cable is connected to the leads.
3. Ground the electronic transmitter, junction box (including the cover),
conduit, and cable shield.
Startup Procedure
To operate the transmitter, perform the following steps. See the installation
diagram in Appendix A, page 25 , for typical valve locations.
1. Locate the block valves and make sure they are closed.
NOTE: The block valve is normally installed at the facility for the purpose of iso-
lating the pressure lines (process being monitored) from the monitoring
instruments.
2. Configure the test manifold’s control valves to connect the input pres -
sure port of the gage pressure transducer to the appropriate pressure lines
(process being monitored). Follow the guidelines in Appendix A that are