Cameron BARTON 764 User manual

BARTON®MODEL 764
DIFFERENTIAL PRESSURE
TRANSMITTER
User Manual
Part No. 9A-C10880, Rev. 05
January 2020
Contents
Section 1—Introduction................................................................................. 5
General.........................................................................................................5
Product Description.......................................................................................5
Di󰀨erential Pressure Unit (DPU) ...............................................................5
Electronic Transmitter................................................................................5
Power Supply............................................................................................5
Specications................................................................................................6
Performance..............................................................................................6
Application.................................................................................................7
Storage:.....................................................................................................8
Section 2—Theory of Operation.................................................................... 9
Basic Components........................................................................................9
Di󰀨erential Pressure Unit (DPU) ...............................................................9
Draining or Venting.....................................................................................9
TemperatureCompensation......................................................................10
Bellows......................................................................................................10
Strain GageAssembly...............................................................................10
Range Springs..........................................................................................10
Electronic Transmitter...............................................................................10
Basic Operation ...........................................................................................11
Reverse Polarity Protection......................................................................11
Regulator.................................................................................................12
Strain Gage Bridge Network....................................................................12
Signal Amplier........................................................................................12
Current Amplier......................................................................................12
Temperature Compensation........................................................................12
Section 3—Installation and Operation........................................................ 13
Unpacking/Inspection..................................................................................13
Pre-Operating Instructions..........................................................................13
Mounting.....................................................................................................13

Table of Contents Model 764 Differential Pressure Transmitter
Vibration..................................................................................................13
Piping..........................................................................................................14
Distance ..................................................................................................14
Slope.......................................................................................................14
Process Temperature.............................................................................. 14
Pulsation..................................................................................................14
Leakage...................................................................................................14
High-Pressure Connection..........................................................................14
Manifolding..................................................................................................14
Electrical Connections................................................................................. 15
Load and Line Resistance Calculations..................................................16
EMI/RFI Shielding.......................................................................................18
Initial Calibration Adjustments.....................................................................19
Calibration Check....................................................................................19
Startup Procedure...................................................................................21
Shutdown Procedure...............................................................................21
Section 4—Maintenance ............................................................................. 22
General Field and Periodic Maintenance....................................................22
DPU Inspection and Cleaning .................................................................22
Pressure Check.......................................................................................22
Cleaning the DPU....................................................................................22
Periodic Calibration ....................................................................................23
Transmitter Cover Removal........................................................................25
Transmitter Cover Reinstallation.............................................................25
Operation of the EGS Quick Disconnect Connector Assembly................... 26
Lead Wire/Connector Replacement............................................................27
Removal of the EGS Quick Disconnect Connector Assembly................. 27
Installation of the EGS Quick Disconnect Connector Assembly.............. 27
Removal of the Barton Style Connector Assembly.................................. 29
Installation of the Barton Style Connector Assembly............................... 29
Troubleshooting..........................................................................................31
Section 5—Assembly Drawing and Parts List........................................... 32
Section 6—Dimensional Drawings ............................................................. 34
Product Warranty........................................................................................35
Product Brand..............................................................................................35

Model 764 Differential Pressure Transmitter Table of Contents
Safety
Before installing this product, become familiar with the installation instruc-
tions presented in Section 3 and all safety notes throughout.
! WARNING:Thissymbolidentiesinformationaboutpracticesorcircum-
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 a󰀨ect instrument operation or
may lead to an instrument response that is not planned.

Table of Contents Model 764 Differential Pressure Transmitter

5
Model 764 Differential Pressure Transmitter Section 1
Section 1—Introduction
General
The Model 764 Dierential Pressure Transmitter provides a 4-20 mA or 10-
50 mA proportional-to-dierential pressure signal for transmission to remote
receiving, control, or readout devices.
The electronic components of the Model 764 transmitter are housed in a
pressure-sealed enclosure. The instruments are designed to operate beyond
their normal operating environmental specications for a limited period of
time under such adverse conditions as may be encountered within the contain-
ment of a nuclear power plant under accident and post-accident conditions.
These adverse environments include severe changes in ambient pressure,
temperature and humidity, seismic events, and radiation exposure.
Product Description
The Model 764 transmitter combines a dierential pressure unit (DPU) with
an electronic circuit. The 4-20 mA or 10-50 mA output is compatible with a
wide range of electronic receiving, control, and readout equipment. The in-
strument utilizes electronic circuits and a molecular-bonded strain gage sens-
ing cantilever beam, actuated directly by the bellows travel within the DPU.
Dierential Pressure Unit (DPU)
The mechanical actuating device for the Model 764 transmitter is a dual
bellows assembly enclosed by a set of two pressure housings. The dual bel-
lows assembly (Figure 2.1, page 9) consists of two internally-connected
bellows, a center block, overrange valves, a temperature compensator, a strain
gage assembly, and range springs. The internal volume of the bellows and
center block is completely lled with a clean, non-corrosive, non-conductive
liquid with a low freezing point and sealed. The motion-sensing cantilever
beam is also sealed within this environment.
Electronic Transmitter
The electronic transmitter supplies either a 4-20 mA or 10-50 mA direct cur-
rent output signal that is proportional to the dierential pressure sensed by the
DPU. The output signal is transmitted over a two-wire transmission line to
remote receiving devices.
Power Supply
A regulated direct current (DC) power supply is required to operate the trans-
mitting loop.

6
Section 1 Model 764 Differential Pressure Transmitter
Specications
Performance
Input Range....................................0-60 inches (water column) to 0-320 psid
Output.............................................4-20 mAor 10-50 mA, direct and reverse acting
Reference Accuracy*......................±0.5% of factory-calibrated span, including e󰀨ects of
conformance (non-linearity), deadband, hysteresis,
and repeatability
Adjustability ....................................±5% eld adjustability of factory-calibrated span,
without a󰀨ecting normal or accident condition perfor-
mance. Span is eld adjustable from 20% to 100%
of factory-calibrated span. Zero is eld adjustable for
up to 30% suppression. Zero or Span adjustments
beyond ±5% a󰀨ect normal and accident condition
performance.Calibration is by the end-point method
with zero and full scale outputs held to ±0.05% of
true.
Sensitivity*......................................±0.01% of factory-calibrated span
Power Requirements......................15 VDC plus 2 VDC per 100 Ohm load to 53 VDC
maximum (4-20 mA)
15 VDC plus 5 VDC per 100 Ohm load to 52 ±1 VDC
(53 VDC maximum) for 10-50 mA
Load Range
(includes line and receiver).............50 Ohms per volt above 15 VDC (4-20 mA)
20 Ohms per volt above 15 VDC (10-50 mA)
Load E󰀨ect* ....................................< ±0.05% of factory-calibrated span per 100 Ohm
change (4-20 mA)
< ±0.1% of factory-calibrated span per 100 Ohm
change (10-50 mA)
Power Supply E󰀨ect*......................< ±0.025% of factory-calibrated span per 1 Volt
change (4-20 mA)
< ±0.05% of factory-calibrated span per 1 Volt
change (10-50 mA)
Suppression....................................100% of calibrated span (factory adjustment), 30%
with potentiometer
Span Control...................................20% to 100% of maximum span (±5% only without
degradation of specications); potentiometer range
is greater than 2:1 at maximum span and greater
than 1.5:1 at minimum span
Noise*.............................................< 0.5% peak-to-peak of factory-calibrated span
Thermal E󰀨ect* (combined
e󰀨ect on zero and span).................±1.0% of factory-calibrated span per 100°F change
from +40°F to +150°F
±1.5% of factory-calibrated span per 100°F change
from +150°F to +320°F
Radiation*.......................................±10.0%@2 x 108 Rads TID Gamma; pressure
boundaries tested to 9 x 108 TID Beta
Seismic:
During Event*.............................< ±5.0% error
After Event*................................< ±0.5% error

7
Model 764 Differential Pressure Transmitter Section 1
LOCA Performance*.......................< ±5.0% error during the rst ve minutes of LOCA
(420°F)
< ±10.0% error thereafter to the conclusion of the
LOCA test, as performed per Document No.
9A-CR3-764-9
The LOCA errors include the cumulative e󰀨ects of
thermal, mechanical, radiation, and seismic aging,
as performed per Document No. 9A-CR3-764-9.
Long Term Drift*..............................±1.0% of factory-calibrated span per year, cumula-
tive
Time Response ..............................< 180 msec. to reach 50% for 10% to 90% step
function
Maximum Safe Working Pressure..3,000 psig
Static Pressure E󰀨ects*
60" WC to 42 psid spans............±0.2% of the factory-calibrated span per 1000 psig
43 to 320 psid spans..................±0.5% of the factory-calibrated span per 1000 psig
Overpressure E󰀨ects
60" WC to 42 psid spans............±0.5% of the factory-calibrated span per 1000 psig
43 to 320 psid spans..................±1.0% of the factory-calibrated span per 1000 psig
Overpressure Limit.........................Up to maximum safe working pressure on either side
of DPU without damage to unit
Process Connections......................1/4" and 1/2" NPT on both high and low pressure
sides
Weight ............................................20.5 pounds
Electrical Interface..........................2-wire (16 AWG) pigtail (20' long)
*Note: Turndown has a directly proportional e󰀨ect on the indicated specications.
IMPORTANT: The Model 764 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
18.
Application
The Model 764 Dierential Pressure Transmitter was subjected to IEEE
323-1974/344-1975 qualications testing which found the device suitable for
functional service in a harsh environment (LOCA/MSLB).
The service conditions associated with the Model 764 Transmitter nuclear ser-
vice qualications are presented below:
Qualied Service Life
(accelerated aging for
1,830 hours at 257ºF......................85 years at normal conditions of 104ºF
54 years at normal conditions of 113ºF
35 years at normal conditions of 122ºF
23 years at normal conditions of 131ºF
10 years at normal conditions of 140ºF
Radiation Exposure........................200 x 106 Rads (TID Gamma)

8
Section 1 Model 764 Differential Pressure Transmitter
DBE Environment...........................Two 10-second temperature ramps to 486ºF maxi-
mum; 24 hour duration chemical spray exposure;
15 day total exposure to saturated steam at 250ºF
minimum
Long Term Severe Environment.....85 days at 200ºF and 95% RH
Seismic Qualications ....................OBE @ 9.0 G (series of 5)
SSE @ 12.5 G
5% critical damping
no resonance in frequencies below 75 Hz
Mechanical Aging ...........................500,000 pressure cycles during accelerated aging;
Cycled electrically to induce stress during acceler-
ated aging;
Vibration cycling using 0.2 G sweeps over the 1-100
Hz range @ 1.0 octave/min.
Storage:
Storage per ANSI N45.2.2-1978 Level B @ 70ºF (20ºC) ±20ºF (±11ºC) in
factory-sealed package for 2.5 years maximum will not aect installed service
life.

9
Model 764 Differential Pressure Transmitter Section 2
Section 2—Theory of Operation
Basic Components
Dierential Pressure Unit (DPU)
HP Housing
Valve Stem
HP Bellows
LP Housing
LP Bellows
Figure 2.1—DPU
The dierential pressure range of the dual-bellows type DPU is determined by
the force required to move the bellows through their normal range of travel.
To provide for various ranges, range springs are incorporated into the Bellows
Unit Assembly (BUA). The range springs, which are available in various
factory assemblies, accurately balance the dierential pressure applied to the
DPU.
In operation, the two bellows (which are connected by the valve stem shown
in Figure 2.1) move in proportion to the dierence in pressure applied across
the BUA. The linear motion of the bellows is picked up by the tip of the sili-
cone strain gage beam, which is actuated directly by the valve stem connect-
ing the two bellows. If the bellows are subjected to a pressure greater than the
dierential pressure range of the DPU, they will move through their normal
range of travel, plus a small additional amount of "overtravel," until the valve
on the stem shaft seals against its valve seat. As the valve closes on the seat, it
"traps" the ll liquid in the bellows, protecting the unit from damage or shift
in calibration.
Since the ll uid is essentially non-compressible, the bellows are fully sup-
ported and cannot rupture regardless of the over-pressure (up to the full rated
pressure of the instrument) applied to the unit. Furthermore, since the unit
contains opposed valves, protection against "overrange" in either direction is
provided.
Draining or Venting. The high and low pressure housings of the DPU are
provided with both top and bottom pressure connections which provide a
draining feature when the unit is used in gas installations, or a venting feature

10
Section 2 Model 764 Differential Pressure Transmitter
when the unit is used in liquid installations, when installed in accordance with
standard practices.
Temperature Compensation. The high pressure side of the DPU has extra
bellows convolutions to provide for expansion and contraction of the ll
liquid caused by ambient temperature changes. These extra convolutions are
connected to the measuring bellows by a passageway to permit the ll liquid
to change volume without materially aecting the internal pressure or the
physical relationship of the measuring bellows.
Bellows. Individual bellows diaphragms are stamped from special order Type
316 ELC (Extra Low Carbon) stainless steel sheets. The diaphragms are as-
sembled and seam welded to form the bellows.
Strain Gage Assembly. The strain gage assembly (Figure 2.2) 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 installed directly into a cutout in the valve stem con-
necting the two bellows of the DPU. Any movement of the bellows in either
direction 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.
Tension Strain Gage
Compression Strain Gage
Beam & Strain Gage Assembly
Figure 2.2—Strain Gage Assembly
Range Springs. The range springs act with the bellows to balance the dier-
ential pressure applied to the unit. The springs are fabricated of a material that
is compatible with the specic bellows material used. The number of springs
and their rate depends on the dierential range desired.
Electronic Transmitter
The DPU senses the dierence in pressure applied across the bellows unit as-
sembly. The pressure causes a linear motion of the bellows which is mechani-
cally transmitted to the strain gages by the strain gage beam. Motion of the
end of the strain gage beam applies tension to one gage and compression on
the other. The gage in tension increases in resistance, while the one under

11
Model 764 Differential Pressure Transmitter Section 2
compression decreases in resistance. The two gages are connected to form
two active arms of a bridge circuit. The bridge output signal is conditioned
and converted to a 4-20 mA or 10-50 mA output signal by the transmitter
electronics.
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 2.3) shows the relationships of the various stages and
the main ow of the electrical currents. As shown, the transmitter, power sup-
ply, 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
main current ows through the current amplier 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 signal amplier. The
current is then returned to the loop. The total loop current ows through the
load and back to the power supply.
Figure 2.3—Operational block diagram
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.

12
Section 2 Model 764 Differential Pressure Transmitter
Regulator
This stage of the circuit regulates that portion of the loop current which is not
calibrated at the current amplier stage, and provides stabilized voltage for
bridge excitation and power for the signal amplier.
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.
Signal Amplier
The signal amplier is an integrated circuit operational amplier which pro-
vides amplication of the strain gage bridge network output voltage.
Current Amplier
The current amplier circuit converts the signal amplier 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 764 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 qualications certication.
IMPORTANT: Combined zero and/or span changes more than ±5% of the factory
calibration can adversely impact transmitter performance. The transmitter
performance may be decreased in direct proportion to the changes to the
factory calibration. If the combined zero and/or span changes represent
a change in the factory calibration by a factor of 2, the transmitter perfor-
mance may be decreased by a factor of 2.

13
Model 764 Differential Pressure Transmitter Section 3
Section 3—Installation and Operation
!WARNING: Failure to follow instructions for removing the transmitter
cover may damage the transmitter cover and case. This could result in
a serious degradation of transmitter performance during design basis
events, resulting in a potential degradation of safety systems. To avoid
the potential for equipment degradation, see Transmitter Cover Removal,
page 25).
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 a󰀨ected.
After nal cleaning, a polyethylene bag is used to protect the instrument from
contamination. This bag should be removed only in a clean area.
Pre-Operating Instructions
The following steps must be performed at the time of installation to ensure
that the instrument will perform to its original calibration.
1. Verify that the transmitter is mounted in an approximately level plane
(see Mounting below).
2. Verify that the transmitter is properly connected to the pressure source
(see Piping, page 14).
3. Verify that electrical connections are in accordance with the schematic
diagram (see Electrical Connections, page 15).
Perform the initial calibration adjustments (see Initial Calibration Adjust-
ments, page 19).
Mounting
Mount the instrument on wall or rack with four 5/16" (8mm) bolts, Grade 5
or better, and torque to 10-20 ft-lb. Mounting structures shall be designed to
avoid resonance and/or keep resulting amplication below 33 Hz. Interfacing
process tubing and conduit shall be supported by the same mounting as the in-
strument base to minimize relative motion of the instrument and connections.
Vibration
Minimize vibration by mounting the instrument on a secure support.

14
Section 3 Model 764 Differential Pressure Transmitter
Piping
The practices described in this section should be followed for all instrument
piping.
Distance
The distance between the primary device and the instrument should be as
short as possible.
Slope
Slope all piping at least one inch per linear foot to prevent liquid or gas en-
trapment in the lines or the instrument.
• Slope all piping downward from the transmitter when used in gas instal-
lations to prevent liquid entrapment.
• Slope all piping upward from the transmitter when used in liquid applica-
tions to prevent gas entrapment.
Process Temperature
If the process temperature exceeds 135°F, provide a minimum of 1-foot of un-
insulated pipe between the instrument and the primary device for each 100°F
above 135°F.
Pulsation
Minimize pulsation. Severe pulsation will aect the performance of the
instrument.
Leakage
Prevent leakage by using a suitable sealing compound on all joints. Measure-
ment errors can be caused by leaks in the piping.
High-Pressure Connection
Connect the high-pressure chamber to the upstream side of the orice or the
high-pressure side in a standard liquid level application.
Manifolding
The use of manifolds is recommended for shutting o sensing lines while
removing or calibrating the instrument.

15
Model 764 Differential Pressure Transmitter Section 3
Electrical Connections
!WARNING: Failure to properly calculate power supply DC output voltage
may result in inaccurate transmitter readings, possibly leading to safety
system performance degradation during design basis events. To avoid
equipment inaccuracy hazards, follow the examples and tables in this
section for determining the proper power supply DC output voltage.
Field wiring connections for the transmitter are presented in Figure 3.1. If the
transmitter is equipped with an EGS Quick Disconnect connector assembly,
make sure the two halves of the connector are secured with the bayonet ring.
See Operation of the EGS Quick Disconnect Connector Assembly, page 26,
for details.
It is important that the total loop resistance be less than the maximum calcu-
lated value and greater than or equal to the minimum value for proper opera-
tion under post-accident conditions. See Figure 3.2, page 16, for reference.
Figure 3.1—Typical eld wiring connections

16
Section 3 Model 764 Differential Pressure Transmitter
Minimum resistance is based upon maximum transmitter power dissipation
(Watts) at the maximum design temperature conditions, and qualied life limited
by heat rise. For proper operation at post-accident conditions, this minimum
resistance must exist.
Figure 3.2—Power supply and loop resistance
Load and Line Resistance Calculations
Use the following method to calculate values of load and line resistance:
Total Loop Resistance (RT) = RLine + RLoad +RExt
Power Supply Voltage = VDC (53 V max. for 4-20 mA or 10-50 mA Systems)
Minimum no load Transmitter Voltage = TVDC (15 V for both 4-20 mA and
10-50 mA Systems)
Maximum no load Transmitter Voltage = TVDC (47.2 V for 4-20 mA and 19 V
for 10-50 mA Systems)
Transmitter Current = IDC (20 mA or 50mA)
RT = TVDC - TVDC
IDC
Example 1 : (Maximum loop resistance for 10-50 mA system):
VDC = 53 Vdc TVDC = 15 Vdc
IDC = 50 mA RT = (53-15) / 0.05 = 760 Ohms

17
Model 764 Differential Pressure Transmitter Section 3
Example 2 : (Maximum loop resistance for 4-20 mA system):
VDC = 53 Vdc TVDC = 15 Vdc
IDC = 20 mA RT = (53-15) / 0.02 = 1900 Ohms
Example 3 : (Calculation to determine maximum loop resistance with power
supply ≥ 15 Vdc, but ≤ 53 Vdc for 10-50 mA systems):
VDC = 40 Vdc TVDC = 15 Vdc
IDC = 50 mA RT = (40-15) / 0.05 = 500 Ohms
Minimum loop resistance is determined based on maximum power supply volt-
age, maximum transmitter current, and maximum no load transmitter voltage.
Example 4 : (Minimum loop resistance for 10-50 mA system):
VDC = 53 Vdc TVDC = 19 Vdc
IDC = 50 mA RT = (53-19) / 0.05= 680 Ohms
For 10-50 mA systems with a 53V power supply, if RLoad = 200 Ohms (Ex-
ample 1, maximum loop resistance and Example 4, minimum loop resis-
tance), then RExt + RLine must be ≥ 480 Ohms, but ≤ 560 Ohms to satisfy both
the maximum and minimum loop resistance values.
For 4-20 mA systems, maximum loop resistance is determined using Example
2, minimum loop resistance is determined using Example 5.
Example 5 : (Minimum loop resistance for 4-20 mA system):
VDC = 53 Vdc TVDC = 47.2 Vdc
IDC = 20 mA RT = (53-47.2) / 0.02 = 290 Ohms
Care must be exercised when calculating the power supply output voltage. A
power supply specied as 50Vdc ±1 volt must be considered a 49Vdc source
to ensure the minimum required voltage at the transmitter. Use the actual
value when available; otherwise, use "worst case" value.
Use Figure 3.2 as a reference to determine if the maximum calculated value
of RT = RLine + RLoad + RExt is correct.

18
Section 3 Model 764 Differential Pressure Transmitter
EMI/RFI Shielding
IMPORTANT: The Model 764 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.
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. The transmitter leads should be housed in solid conduit up to the junction
box where the shielded eld cable is connected to the transmitter leads.
3. Ground the electronic transmitter, junction box (including the cover),
conduit, and cable shield.

19
Model 764 Differential Pressure Transmitter Section 3
Initial Calibration Adjustments
If a transmitter is installed after an extended period of storage, a calibration
test should be performed before operating the transmitter to ensure correct
performance.
Accuracy of the test equipment used for the calibration test should be ap-
proximately four times the accuracy of the instrument under test. See Table
4.1, page 23, for general requirements.
Calibration Check
The transmitter should be tested at minimum, maximum and 50% calibrated
range pressures for at least three cycles. See Table 3.1—Calibration Check-
points, page 20, for recommended transmitter output values and the associ-
ated tolerances, in current and voltage, for 4-20 mA and 10-50 mA outputs.
To test the transmitter calibration, perform the following steps:
1. Remove the calibration access plugs from the transmitter cover using a
socket or a wrench.
IMPORTANT: If there are no calibration access plugs in the cover, the cover must be
removed to adjust calibration. See Transmitter Cover Removal, page
25, for instructions.
2. Connect the electrical readout device to the transmitter as shown in Fig-
ure 3.3 for either current or voltage readout. If the transmitter is equipped
with an EGS Quick Disconnect connector assembly, secure the two
mating connectors with the bayonet ring (see Figure 4.1, page 26, for
details).
3. With minimum calibration pressure applied, compare the output signal to
the recommended value in Table 3.1, and adjust the zero control potenti-
ometer in the compensating direction as required.
4. Apply calibration pressure corresponding to maximum output, compare
the output signal to the recommended value in Table 3.1, and adjust the
span control potentiometer in the compensating direction as required.
5. Repeat steps 3 and 4 as necessary to obtain desired accuracy. (Zero and
span controls have a minimum of interaction when adjusted, so this step
may or may not be required.)
6. Apply 50% calibration pressure and verify that the output is within Table
3.1 specications. If it is not within recommended specications,
recalibrate the transmitter using the calibration procedure on page 23
or return the transmitter to the factory.

20
Section 3 Model 764 Differential Pressure Transmitter
Figure 3.3—Electrical connections for calibration
Table 3.1—Calibration Checkpoints
Applied Calibration
Pressure Check-
point (% of Full
Scale)
Output*
4-20 mA Transmitter** 10-50 mA Transmitter***
Current
(±0.08 mA) Voltage (±0.04 Vdc Current (±0.2 mA) Voltage (±0.04 Vdc)
0% 4 mA 2 Vdc 10 mA 2 Vdc
25% 8 mA 4 Vdc 20 mA 4 Vdc
50% 12 mA 6 Vdc 30 mA 6 Vdc
75% 16 mA 8 Vdc 40 mA 8 Vdc
100% 20 mA 10 Vdc 50 mA 10 Vdc
*This value includes the e󰀨ects of conformance (non-linearity), deadband, hysteresis, and repeatability.
**This value was obtained using a 500-Ohm load resistor.
***This value was obtained using a 200-Ohm load resistor.
7. Replace the calibration access plugs as follows (or if the cover has no
calibration access plugs and was removed, see page 25 for instructions
on replacing the cover).
a. Replacement of the calibration plug O-rings is recommended (coat
with a small amount of silicone grease).
b. Install the calibration plugs.
c. Tighten the plugs until they are snug (no applicable torque values).
IMPORTANT: The plugs should be tightened only to prevent loosening due to vibration
without interfering with zero and span potentiometer adjustments.