Cameron BARTON 753A Manual de usuario
BARTON®MODEL 753A
GAGE PRESSURE TRANSMITTER
User Manual
Part No. 9A-10840, Rev. 02
March 2020
Contents
Safety............................................................................................................ 2
Section 1—Introduction................................................................................. 3
General ......................................................................................................... 3
Product Description....................................................................................... 3
Gage Pressure Transducer ...................................................................... 3
Electronic Transmitter................................................................................ 3
Power Supply ............................................................................................ 4
Zero and Span Control.................................................................................. 4
Zero Control .............................................................................................. 4
Span Control ............................................................................................. 4
Specications ............................................................................................... 5
Section 2—Theory of Operation.................................................................... 7
Basic Components........................................................................................ 7
Gage Pressure Transducer ....................................................................... 7
Electronic Transmitter................................................................................ 7
Basic Operation ............................................................................................ 7
Surge Voltage Protection Circuit .............................................................. 8
Reverse Polarity Protection....................................................................... 8
Regulator................................................................................................... 8
Strain Gage Bridge Network ..................................................................... 8
Signal Amplier.......................................................................................... 9
Current Amplier........................................................................................ 9
Temperature Compensation.......................................................................... 9
Section 3—Installation, Startup, and Shutdown........................................ 10
Overview..................................................................................................... 10
Unpacking/Inspection.................................................................................. 10
Initial Calibration Check .............................................................................. 10
Mounting ..................................................................................................... 10
Wall or Rack Mounting ............................................................................ 10
Piping Guidelines.........................................................................................11
Electrical Connections ................................................................................11
Loop Resistance Calculations................................................................. 13
Maximum Loop Resistance..................................................................... 14
2
Safety
Before installing this product, become familiar with the installation instruc-
tions presented in Section 3 and all safety notes throughout.
!WARNING:Thissymbolidentiesinformationaboutpracticesorcircum-
stances that can lead to personal injury or death, property damage, or
economic loss.
CAUTION: Indicates actions or procedures which if not performed correctly
may lead to personal injury or incorrect function of the instrument
or connected equipment.
IMPORTANT: Indicates actions or procedures which may aect instrument operation or
may lead to an instrument response that is not planned.
EMI/RFI Shielding.........................................................................................14
Startup Procedure.........................................................................................14
Shutdown Procedure....................................................................................15
Section 4—Calibration and Maintenance.....................................................16
General Field and Periodic Maintenance......................................................16
Electronic Transmitter................................................................................16
Calibration.....................................................................................................16
Test Equipment.............................................................................................16
Electrical Connections for Calibration.......................................................17
Calibration Checkpoints............................................................................18
Calibration Procedure................................................................................18
Troubleshooting............................................................................................20
Section 5-Assembly Drawing and Parts List...............................................21
Section 6-Dimensional Drawings..................................................................23
Appendix A.....................................................................................................25
Safety Precautions........................................................................................25
Flow Application........................................................................................25
Typical Piping/Startup Example....................................................................25
Gas Flow...................................................................................................25
Product Warranty............................................................................................26
Product Brand.................................................................................................26
3
Model 753A Gage Pressure Transmitter Section 1
Section 1—Introduction
General
The Model 753A Gage Pressure Transmitter provides a 4-20 mA or 10-50 mA
proportional-to-gage-pressure signal for transmission to remote receiving,
control, or readout devices. Sources of gage pressure include liquid and gas
ow through orice plates, nozzles or venturis; static line pressures, etc.
Product Description
The Model 753A utilizes a gage pressure transducer functioning in combina-
tion with an electronic circuit. The 4-20 mA or 10-50 mA output is compati-
ble with a wide range of electronic receiving, control, and readout equipment.
The instrument utilizes surface mount electronic components, electronic
circuits and a molecular-bonded strain gage sensing cantilever beam, actuated
directly by a Bourdon tube pressure sensing element. In many applications,
the electrical connections are contained within a junction box, as shown in
Figure 3.1, page 12. However, the junction box is optional.
Gage Pressure Transducer
The mechanical actuating device for the Model 753A transmitter is a C-type
Bourdon tube pressure sensing element enclosed in a pressure housing.
Figure 1.1—Gage pressure transducer assembly
Electronic Transmitter
The electronic transmitter supplies a 4-20 mA or 10-50 mA direct current
output signal that is proportional to the gage pressure sensed by the Bourdon
tube. The output signal is transmitted over two wires to remote receiving
devices.
4
Section 1 Model 753A Gage Pressure Transmitter
Power Supply
A regulated direct current (DC) power supply is required to operate the trans-
mitting loop. The voltage required will depend on the total loop resistance
(load resistor, cable wiring, and any other resistance in the loop) as shown in
Figure 3.3, page 13. Table 3.1, page 13 shows the resistances in ohms
per 1000 feet of wiring for the various cable wire sizes. Once the total loop
resistance has been determined, the power supply voltage can be calculated as
follows:
• For 4-20 mA output: VDC = 12 VDC + 2 VDC per 100-ohms load
• For 10-50 mA output: VDC = 12 VDC + 5 VDC per 100-ohms load
Exercise care when calculating the power supply voltage. A power supply
specied at 50 VDC ±1 volt must be considered a 49 VDC source to insure
the minimum required voltage at the transmitter. Use the actual value when
available. Otherwise, use the "worst case" value.
Power supply wiring connections are shown in Figures 3.1 and 3.2, page
12.
Zero and Span Control
The transmitter has two 10-turn potentiometers—one for zero adjustments,
the other for span control. With these two controls, measurement can be made
between any two points within the rated transmitter span. However, to ensure
a high level of accuracy, combined zero and span adjustments should never
exceed ±5% of the factory calibration.
IMPORTANT: Combined zero and/or span eld adjustments exceeding ±5% of the fac-
tory calibration can alter transmitter performance in direct proportion to
the changes to the factory calibration. For example, if combined adjust-
ments to zero and span change the factory calibration by a factor of 2,
transmitter performance may be decreased by a factor of 2.
Zero Control
During calibration, the zero control is used to adjust the instrument’s output
signal to 4 mA or 10 mA at the minimum pressure setting of the instrument.
Span Control
When a transmitter leaves the factory, it has a xed range of 0-200 psig,
0-2500 psig, etc. Typically the output from the transmitter varies from 4-20
mA or 10-50 mA. This output is linear with the measured variable, as shown
in Figure 1.2, page 5.
5
Model 753A Gage Pressure Transmitter Section 1
During calibration, the span control is used to adjust the instrument’s output
to 20 mA or 50 mA output signal at the maximum pressure setting of the
instrument.
10
50
OR
ELECTRONIC SIGNAL mA
4
20
20 40 60 80 100
% OF FULL SCALE DP RANGE
Figure 1.2—Output calibrated to upper limit of DP range
Specications
Input Range.................................... 0-108 psig to 0-4620 psig
(Consult factory for other ranges)
Output............................................. 4-20 mA or 10-50 mA, direct or reverse acting
Reference Accuracy*...................... ±0.5% of factory-calibrated span, including eects of
non-linearity, hysteresis, and repeatability
(±0.25% accuracy optional)
Zero/Span Adjustments .................. Combined zero/span eld adjustments are limited to
±5% of factory-calibrated span. See Zero Suppres-
sion and Custom Span for additional options.
Zero Suppression ........................... Available as an option.
0% to 50% suppression of factory-calibrated span
Custom Span.................................. Available as an option.
20% to 100% of factory-calibrated span
Sensitivity*...................................... ±0.01% of factory-calibrated span
Power Requirements (see Figure 3.3, page 13)
4-20 mA....................................... 12 VDC plus 2 VDC per 100-ohms load (to 70 VDC
maximum)
10-50 mA..................................... 12 VDC plus 5 VDC per 100-ohms load (to 70 VDC
maximum)
Load Range
(includes line and receiver; see Figure 3.3, page 13)
4-20 mA....................................... 50 ohms per volt above 12 VDC (to 2900 ohms
maximum)
10-50 mA..................................... 20 ohms per volt above 12 VDC (to 1160 ohms
maximum)
Load Eect*
4-20 mA....................................... ±0.025% of factory-calibrated span per 100-ohms
change
10-50 mA..................................... ±0.05% of factory-calibrated span per 100-ohms
change
6
Section 1 Model 753A Gage Pressure Transmitter
Power Supply Eect*
4-20 mA....................................... ±0.025% of factory-calibrated span per 1 Volt
change
10-50 mA..................................... ±0.05% of factory-calibrated span per 1 Volt change
Noise*............................................. 0.2% (peak-to-peak) maximum of factory-calibrated
span
Thermal Eect*
(combined eect on zero
and span)........................................ ±1.0% of factory-calibrated span per 100ºF change
within the operating temperature range selected
Operating Temperature................... 40ºF to 135ºF (standard), -15ºF to +135ºF (optional)
Overpressure limit .......................... 1.5 × factory calibrated range without damage to unit
Process Connections...................... 1/4" NPT (female)
Weight ............................................ 8 lb
Electrical Interface.......................... 1/2 inch conduit connections to internal screw termi-
nals (external junction box optional)
*Note: Turndown has a directly proportional eect on the indicated specications. Zero
or span eld adjustments beyond ±5% may aect indicated performance. Calibration is
by the end-point method with zero and full scale outputs held to ±0.5% of true calibrated
values.
IMPORTANT: The Model 753A transmitter has no integral electronic interference sup-
pression features. If an instrument is to be installed in an area containing
EMI/RFI sources and this interference cannot be tolerated, take precau-
tions to protect the transmitter signal. See also EMI/RFI Shielding, page
14. An optional EMI/RFI lter system is available upon request.
7
Model 753A Gage Pressure Transmitter Section 2
Section 2—Theory of Operation
Basic Components
Gage Pressure Transducer
The gage pressure sensing element is a C-type Bourdon tube. The C-type
Bourdon tube is an arc-shaped metal tube, elliptical in cross-section and open
at one end. The open end is attached to the pressure source. The closed end is
free to move. When pressure is applied to the inside of the tube through the
open end, the tube loses its circular shape and the sensing element is actuated.
The gage pressure transducer range is determined by the force required to
move the C-type Bourdon tube bellows through its normal range of travel. To
provide for various ranges, tubes are designed with dierent wall thicknesses
and degrees of tube cross-section distortion.
Strain Gage Assembly. The strain gage assembly consists of a strain gage
beam and a glass-to-metal seal feed-through assembly. Strain gages are
bonded to opposite sides of the strain gage beam. The end of the strain gage
beam is connected to the gage pressure sensing element. Any movement of
the sensor causes a corresponding linear movement of the strain gage beam
which acts upon the strain gages. Any action of the strain gages is monitored
by the electronic transmitter circuit.
Electronic Transmitter
The 753A transmitter senses the pressure applied at the input of the gage pres-
sure assembly and the electronic circuit converts to a 4-20 mA or 10-50 mA
output signal. The pressure causes the closed end of the C-type Bourdon tube
to move and the movement is mechanically transmitted to the strain gages by
the strain gage beam. Motion of the end of the strain gage beam applies ten-
sion to one gage and compression on the other. The gage in tension increases
in resistance, while the one under compression decreases in resistance. The
two gages are connected to form two active arms of a bridge circuit.
Basic Operation
The electronic transmitter is basically a loop current regulating device, where
loop current is controlled by an input of mechanical force or motion. The
block diagram (Figure 2.1, page 8) shows the relationships of the various
stages and the main ow of the electrical currents. As shown, the transmitter,
power supply, and load (line plus receiving device) are connected in series.
The current from the power supply enters the transmitter, passes through the
reverse polarity protecting diode, then divides into two separate paths. The
8
Section 2 Model 753A Gage Pressure Transmitter
main current ows through the current amplier stage and returns to the loop.
The remainder of the current passes through the electronic regulator where it
divides into two paths, through the bridge circuit and the voltage amplier.
The current is then returned to the loop. The total loop current ows through
the load and back to the power supply.
Surge Voltage Protection Circuit
Two gas discharge tubes and a Zener diode are placed in the input circuit to
prevent transient voltages from entering the transmitter circuit.
Reverse Polarity Protection
Reverse input polarity protection is provided by the forward-conducting
diode. In the event the polarity of the input is reversed, the diode blocks the
input and prevents the reversed input power from damaging the electronic
circuit components. The diode can accommodate a maximum of 80 Volts
without damage.
Regulator
This stage of the circuit regulates that portion of the loop current which is not
calibrated at the current amplier stage, and provides stabilized voltage for
bridge excitation and power for the signal amplier.
Figure 2.1—Operational block diagram
Strain Gage Bridge Network
The strain gage bridge network consists of two silicone piezo-resistive strain
sensors, the zero adjusting potentiometer, bridge completion resistors, and the
temperature compensation components.
9
Model 753A Gage Pressure Transmitter Section 2
Signal Amplier
The signal amplier is an integrated circuit operational amplier which pro-
vides amplication of the strain gage bridge network output voltage.
Current Amplier
The current amplier circuit converts the signal amplier output voltage to
current. The amount of current is precisely regulated with the feedback net-
work to make it proportional to the bridge output.
Temperature Compensation
The Model 753A transmitter is temperature-compensated at the factory. Only
those repairs described in Section 4 of this manual may be performed in the
eld without voiding the certied performance.
10
Section 3 Model 753A Gage Pressure Transmitter
Section 3—Installation, Startup, and Shutdown
Overview
This section describes the steps required to install the instrument so that it
will perform to its original factory calibration condition. Installation tasks
include
•initial calibration check
• mounting the transmitter
• installing piping
•installing eld wiring
Unpacking/Inspection
The instrument should be inspected at the time of unpacking to detect any
damage that may have occurred during shipment.
IMPORTANT: The unit was checked for accuracy at the factory. Do not change any of
the settings during examination or accuracy will be aected.
If the transmitter is Class II cleaned, it is shipped in a polyethylene bag to
protect the instrument from contamination. Remove this bag only in a clean
area.
Initial Calibration Check
The Model 753A transmitter is factory-calibrated. However, to ensure that the
calibration is intact following shipping, a calibration check is recommended
prior to operating the instrument. See Calibration, page 16, for step-by-step
instructions. Record the "as found" values and recalibrate, if necessary.
Mounting
Mount the transmitter so that the transmitter cover is facing the operator and
the controls are on the right side. Use mounting structures that are designed to
minimize vibration and prevent resonance. Support connected process tubing
and conduit using the same mounting as the instrument base to minimize rela-
tive motion of the instrument and connections.
Wall or Rack Mounting
1. Locate and drill four bracket mounting holes in the mounting surface.
2. Attach the instrument to the wall using 5/16" (8 mm) bolts, Grade 5 or
better, and torque to 10-20 ft-lb.
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