Cameron Barton 752, Руководство пользователя

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Model 752 and 752A Differential Pressure Transmitter Section 3
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 752 and 752A transmitters have no integral electronic interference
suppression features. If an instrument is to be installed in an area con-
taining 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
diagrams in Appendix A, page A-1 , 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 pressure
ports of the DPU to the appropriate pressure lines (process being