Cameron Barton 752, User Manual

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Section 4 Model 752 and 752A Differential Pressure Transmitters
Table 4.1—Calibration Equipment
Equipment Requirements
Digital Voltmeter ±0.05% of reading accuracy at 10 VDC scale
Power Supply 12-70 Vdc, 60 mA minimum, regulation 3%, ripple 1% (see Electrical
Connections, page 14 )
Precision Load Resistor 200 ohms, ±0.05%, 1W (10-50 mA transmitter) 500 ohms, ±0.05%,
1W (4-20 mA transmitter)
Pressure Source Provides zero to full scale pressure (Accuracy: 4 times the accuracy
of the instrument under test)
Electrical Connections for Calibration
The electrical connections required for calibrating the transmitter are shown
in Figure 4.1.
!
WARNING: Ensure that the condulet cover is secure before applying
power to instrument when used in hazardous areas. Failure to do this
may result in personal injury or property damage.
+
GND
Precision
DC Voltmeter
Power Supply
+
+
Load
Resistor
500 ohms, 4-20 mA systems
200 ohms, 10-50 mA systems
Model
752/752A
+
Milliammeter
(optional)
Figure 4.1—Electrical connections for calibration
Flexible cable is recommended for electrical connections to the instrument.
Perform the following steps to complete field wiring.
1. Connect the power supply and the DC voltmeter to the transmitter as
shown in Figure 4.1.
2. Connect a milliammeter as shown, if desired.
3. Determine the total loop resistance required for the installation, using
Figure 3.3, page 16 , for reference. The total loop resistance must be less
than the maximum calculated value. Table 3.1, page 16, provides loop
resistance values for various cable wire sizes.