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MODEL 761
Absolute Capacitance Manometer
OPERATING INSTRUCTIONS
159 Swanson Road, Boxborough, MA 01719-1304
Tel: 800-257-3872/978-263-1400, Fax 978-264-0292
Email: sales@setra.com, Web: www.setra.com
SS761 RevB. 12/2014
Toll Free: 800-257-3872
978-263-1400
Fax: 978-264-0292
sales@setra.com | www.setra.com
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Contents
1.0 Introduction ..............................................................................................1
2.0 Mechanical Installation .........................................................................2
3.0 Electrical Installation ...............................................................................4
4.0 Operation ....................................................................................................6
5.0 Calibration and Adjustment of Zero Output .................................7
5. 1 Checking & Adjustment of Zero Output .................................7
5. 2 Span (Full Scale) Adjustment and Calibration ...................7
6.0 Maintenance & Troubleshooting .......................................................8
7.0 Specications ............................................................................................9
8.0 Reordering Data ....................................................................................10
9.0 Returning Products for Repair ....................................................... 10
10.0 Warranty & Limitation of Liability ................................................11
11.0 FORM 761ERN RETURN OF SETRA SYSTEMS
PRODUCTDECLARATION ............................................................... 13
11.0 RETURN OF SETRA SYSTEMS PRODUCT-DECLARATION
(Form 761ERN)
EXPECTED RETURN NUMBER _______________________________________________
You must:
• Know about all of the substances which have been used and produced in the
product before you complete this Declaration.
• Contact your supplier if you have any questions and for an ERN Number.
• Send this form to your supplier with the return of the product.
SECTION 1: Product
A. Model Number _____________________
B. Serial Number ______________________
C. Has the product been used, tested or operated?
Yes - Go to Section 2 No - Go to Section 4
SECTION 2: Substances in Contact with the Product
A. Radioactive* Yes No
B. Biologically Active Yes No
C. Dangerous to Human Health and Safety? Yes No
* Note: Your supplier will not accept delivery of any products that are contaminated
with radioactive substances, unless you:
• Decontaminate the products
• Provide proof of decontamination
YOU MUST CONTACT YOUR SUPPLIER FOR ADVICE BEFORE YOU RETURN SUCH PRODUCTS
If you have answered “no” to all of these questions, go to Section 4.
Substance Name Chemical
Symbol
1.
2.
3.
4.
5.
6.
SECTION 3: List of Substances in Contact with the Product
SECTION 4: Return Information
Reason for return and symptoms of malfunction: ______________________________
_______________________________________________________________________
If you have a warranty claim:
• Who did you buy the product from?: _______________________________________
• Give the supplier’s invoice number or your purchase order number: ______________
SECTION 5: Declaration
Print your Name: _______________________ Print Your Job Title: ________________
Print Your Company Name: ________________________________________________
Print Your Address: _______________________________________________________
Telephone Number: ____________________ Date of Product Return:_____________
I have made reasonable inquiry and I have supplied accurate information in this
Declaration. I have not withheld any information. I have followed the Return of Setra
Systems Product Procedure.
Signed: ______________________________ Date: ___________________
Precautions Required (eg: use
protective gloves, etc.)
Actions Required After
Spillage or Human Contact
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1.0 Introduction
Setra’s Model 761 capacitance manometer is a temperature compensated,
vacuum manometer designed for accurate and repeatable vacuum mea-
surements.
The Model 761 operates from a 13-30 VDC power supply and provides a
0-10 VDC or 0-5 VDC signal output that is linear with pressure and indepen-
dent of gas composition. It is congured with a 15 pin D-Sub with “plug
and play” industry standard pinouts. The Model 761 is pin for pin compatible with other competitive capacitance manometers. Superior EMI/RFI
performance is achieved by the use of a metal case in conjunction with
surge and ESD suppression components and RFI ltering on the inputs and
outputs. Inconel® is used for all wetted materials for compatibility with corrosive gases. A wide range of pressure/vacuum ttings are available.
The high accuracy pressure sensing element used in the Model 761 has
been developed from Setra’s patented variable capacitance sensing technology. An electrically isolated, centrally located feed through assembly
supports a circular electrode in close proximity to the back surface of the
diaphragm. Together, the electrode and diaphragm form a variable capacitor within a small reference vacuum chamber. As the pressure increases,
the diaphragm deects and the gap between the electrode and diaphragm
decreases, causing an increase in the capacitance. This change in capaci-
tance is detected and converted to a highly accurate linear DC electronic
signal by Setra’s unique custom circuit.
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Excellent zero stability and thermal insensitivity are achieved through
the patented sensor design. The Model 761 sensor contains no fragile or
complex parts as found in ceramic based capacitance manometers. The all
welded construction eliminates stability issues inherent in other designs
due to frictional contact between dissimilar materials.
US Pat. 8,893,555
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2.0 Mechanical Installation
Remove all packaging material and the protective ange cover and
visually check the Model 761. If the Model 761 appears damaged, notify
Setra Systems or your supplier immediately. Retain packaging materials
for inspection. Do not use if damaged. If the Model 761 is not going to
be used immediately, replace the protective ange cover and store in an
area where the temperature range is controlled between -20 to +80°C.
The Model 761 can be mounted in any orientation on the vacuum
system. To avoid the buildup of debris or condensable material in the
measurement cavity of the Model 761 (which may cause measurement
errors), we recommend that you install the Model 761 vertically with the
tube facing down. Outline drawings showing the external dimensions
are shown in Figures 1 - 3.
To connect the Model 761 to your system use the appropriate hardware
for the type of tting:
• Use a Cajon® Ultra Torr type of compression coupling to connect to
the O.5” OD tube.
• Use an O-ring/centering ring and corresponding clamp to connect to
the NW16, 25 and 40 ange options.
Note: a stepped O-ring carrier may be used to connect the NW16 ange to an NW10
ange on the system.
• Use a Male 8 VCR™ style face seal tting and sealing washer to
connect to the Female Swivel 8 VCR™ style face seal tting.
Note: Tighten threaded ttings or clamps in accordance with the manu-
facturer’s specications.
Calibration Services
Setra maintains a complete calibration facility that is traceable to the
National Institute of Standards & Technology (NIST). If you would like to recalibrate or recertify your Setra pressure transducers or transmitters, please
call our Repair Department at 800-257-3872 (978-263-1400) for scheduling.
10.0 Warranty & Limitation of Liability
SETRA warrants its products to be free from defects in materials and workmanship, subject to the following terms and conditions: Without charge, SETRA
will repair or replace products found to be defective in materials or workmanship within the warranty period; provided that:
a) the product has not been subjected to abuse, neglect, accident, incor-
rect wiring not our own, improper installation or servicing, or use in
violation of instructions furnished by SETRA;
b) the product has not been repaired or altered by anyone except SETRA or
its authorized service agencies;
c) the serial number or date code has not been removed, defaced, or oth-
erwise changed; and
d) examination discloses, in the judgment of SETRA, the defect in materials
or workmanship developed under normal installation, use and service;
e) SETRA is notied in advance of and the product is returned to SETRA
transportation prepaid.
Unless otherwise specied in a manual or warranty card, or agreed to in writing and signed by a SETRA ocer, SETRA pressure and acceleration products
shall be warranted for one year from date of sale.
The foregoing warranty is in lieu of all warranties, express, implied or statutory,
including but not limited to, any implied warranty of merchantability for a
particular purpose.
SETRA’s liability for breach of warranty is limited to repair or replacement, or
if the goods cannot be repaired or replaced, to a refund of the purchase price.
SETRA’s liability for all other breaches is limited to a refund of the purchase
price. In no instance shall SETRA be liable for incidental or consequential
damages arising from a breach of warranty, or from the use or installation of
its products.
No representative or person is authorized to give any warranty other than as
set out above or to assume for SETRA any other liability in connection with the
sale of its products.
2
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2.36
59.9
2.36
59.9
15 PIN D-SUB
CONNECTOR
.17
4.2
3.50
88.9
1.21
30.6
.50
12.7
1.36
NW 40
2.16
NW25
1.58
NW 16
1.18
761G
A
Figure 1: Outline drawing of 15 pin D connector, 0.5” OD tube.
Model
761G = 761
Range
001T = 1 Torr
Pressure
A = Absolute
Type of Fitting
Standard
4T = 0.5” OD Tube
N1 = ISO NW16
N2 = ISO NW25
N4 = ISO NW40
D8 = 8VCR®, Female swivel
2B = 0-5 VDC
2C = 0-10 VDC
Output
Elec. Termination
D2 = 15 Pin D-Sub
Accuracy
Standard
K = ±0.5% of Reading
A = ±0.25% of
Reading
8.0 Reordering Data
Example: To order a 1 Torr FS unit with ISO NW16 tting, 0-10 VDC output,
15 pin D-Sub connector and an accuracy of ±0.25% Reading, the order code
would be: 761G001TAN12CD2A.
9.0 Returning the Model 761 for Repair
Setra Systems cannot accept a Model 761 for repair unless the Form
761ERN is completed. Contact Setra Systems for an ERN Number or the
Form 761ERN. Form 761ERN is included in this guide on page 15.
Please contact a Setra application engineer (800-257-3872, 978-263-1400)
before returning unit for repair to review information relative to your
application. Many times only minor eld adjustments may be necessary.
When returning a product to Setra, the material should be carefully pack-
aged and shipped prepaid to:
Setra Systems, Inc.
159 Swanson Road
Boxborough, MA 01719-1304
Attn: Repair Department
To assure prompt handling, please supply the following information and
include it inside the package of returned material:
1. Name and phone number of person to contact.
2. Shipping and billing instructions.
3. Full description of the malfunction.
4. Identify any hazardous material used with product.
Notes: Please remove any pressure ttings and plumbing that you have
installed and enclose any required mating electrical connectors and wiring
diagrams. Allow approximately 3 weeks after receipt at Setra for the repair
and return of the unit. Non-warranty repairs will not be made without
customer approval and a purchase order to cover repair charges.
Figure 2: Outline drawing showing optional ISO NW vacuum tting.
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Figure 3: Outline drawing showing optional VCR™ style face seal
1.95
2.47
.88
1.06"
ACROSS FLATS
#8 FEMALE VCR
vacuum tting.
3.0 Electrical Installation
The Model 761 operates from a 13-30 VDC power supply.
The Model 761 is factory congured for either a 0-5 VDC output or 0-10
VDC output.
The pin out for the D-sub, 15 pin connector is shown in Figure 5, page 5.
A schematic diagram of the recommended electrical connections to the
D-sub, 15 pin connector is shown in Figure 6, page 5.
Note 1: The ground of any external power supply and readout system should be the
same as the transducer ground (chassis ground) to minimize any possible ground
loops which may eect the performance and stability of the transducer.
Note 2: The Model 761 meets CE mark requirements and complies with EMC Direc-
tive 2004/108/EC. To ensure compliance when installed, an overall metal braided
shielded cable (and metal shielded connectors for the D sub connector option)
connected to chassis ground at both ends is required.
equivalent is recommended.
Note 3: It is recommended that the 761 be powered with a linear power supply.
Innappropriately used switching power supplies can degrade performance.
Note 4: Do not operate this product in an explosive enivornment.
Belden 9941 cable or
7.0 Specications
Performance Data:
Accuracy
Resolution: ≤0.005% FS
Long Term Stability: <±0.25% FS/YR, excluding environmental
eects
Thermal eects
Compensated Range: 15 to +40°C
Zero Shift: < ± 0.02% FS / °C
Span Shift: < ± 0.04% RDG / °C
Proof Pressure: 45 psia
Burst Pressure: > 100psi
Operating Temperature: 5 to +50°C
Storage Temperature: -20 to +80°C
Electrical Data:
Connector: 15 pin D-Sub
Excitation: 13 to 30 VDC for 0-10 VDC
9 to 30 VDC for 0-5 VDC
Output: 0 - 10 V DC or 0 - 5 V DC
Output Maximum Load: >10 k ohms
Power Consumption: < 10 mA
EMC Performance: 2004/108/EC
Response Time: < 20 msec
Physical Description:
Case: Powder Coated Cast Aluminum
Pressure Fittings: 0.5” OD Tube; other ttings available; see reorder
Wetted Materials4: Inconel®
Measurement cavity volume5: <5 cc
Weight: < 14oz
Notes:
1. Accuracy is expressed as % of reading. However, near Zero, the accuracy is limited by the
resolution of the instrument. So, the accuracy is more correctly stated as the greater of ±0.50%
reading or ±0.005% FS. (For the optional accuracy, this becomes the greater of ±0.25% reading
or ±0.005% FS).
2. Includes non-linearity, non-repeatability and hysteresis
3. Units calibrated at nominal 20ºC
4. Wetted material is for 0.5” tube option only. Other ange options will add stainless steel.
5. Maximum cavity volume including the 0.5” OD tube volume. Other ange options will add
wetted volume.
1,2,3
: < ± 0.5% of Reading
Optional < ± 0.25% of Reading
data page
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PIN 1
PIN 8
PIN 9
PIN 15
Signal Output
Chassis ground Shielded cable
1 .0 0 0 0
0V
0V
13-30 VDC
2
5
7
12
15
15 position D-Sub
Connector on
Model 761
Power Supply
Digital volmeter/
readout
6.0 Maintenance & Troubleshooting
There are no general maintenance requirements for the Model 761 other than
periodic zero adjustment. If the unit fails to operate when received or if the unit
appears damaged, notify Setra Systems or your supplier immediately. Retain
packaging materials for inspection. Do not use if damaged. If the Model 761 is
not going to be used immediately then replace the protective ange cover and
store in suitable conditions described in Section 2.
If no obvious damage has occurred a few simple checks can be made to verify
proper installation. Table 2 shows the solution to common problems with the
installation. If none of these problems / solutions are applicable, please contact
a Setra Systems applications engineer for further assistance.
Problem Cause Solution
No signal output Incorrect or no supply voltage Ensure power supply is used as speci-
Signal output reads
over-range
Signal output reads
under-range
Unstable signal Chassis ground not connected Ensure common chassis ground be-
Table 2: Common Installation Problems & Solutions
ed in Section 2
Readout display short circuit or
incorrect impedance
Incorrect wiring Ensure wiring conforms to diagrams in
Potential dierence between
chassis ground of unit, power
supply & readout/display
Incorrect zero adjustment Adjust zero per section 5.1
Readout display incorrect
impedance
Incorrect wiring polarity to
readout display
Unstable or unregulated Use a regulated power supply as
Electrical noise on chassis
ground
Ensure impedance of readout unit is
>10 k
Section 4.2
Ensure common chassis ground be-
tween unit, power supply & display
Ensure impedance of readout unit is
>10 k
Ensure wiring conforms to diagrams in
Section 4.2
tween unit, power supply and display
specied in Section 2
Ensure common chassis ground be-
tween power supply & display
Figure 5: Pin out of D-sub Connector (Code D2)
Figure 6: Electrical Connection Schematic – D-sub 15-pin Connector
Pin Location Function
2 Signal Output
5 Power Supply Common
7 Power Supply, 13-30 VDC
12 Signal Output Common
15 Chassis Ground
1,3,4,6,8,9,10,11,13,14 Not used
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4.0 OPERATION
Z
Mechanically connect the Model 761 to the vacuum chamber. As explained
in Section 2, then electrically connect as shown in Section 3. For the most
accurate pressure measurement, allow the Model 761 to warm up for at
least 15 minutes. After installation, periodically check the zero output reading to verify correct output. Adjust the zero potentiometer if incorrect (See
Section 5 for zero adjustment instructions).
If the unit was just received or stored at an extreme temperature, allow 12
hours for it to acclimate. It is recommended that the Model 761 zero output
be nulled after installation.
The signal output of the Model 761 is linear with pressure; e.g., for a 10 VDC
FS Model 761, 10 VDC equals 100% FS output, 1 VDC equals 10% FS output.
Table 1 indicates the lowest pressures available for reading and pressure
control for each range of the Model 761. The lowest suggested pressure
available for reading is limited by the resolution and the accuracy of the
Model 761. This is directly related to the electrical noise on the signal
output and can be signicantly eected by incorrect electrical ground connection, or connection to an electronically noisy power supply or readout
instrument. Improved results may be obtained if the transducer is operated in an environment with stable temperature and air ow. The lowest
recommended pressure used for control applications, such as a closed loop
downstream pressure control system, is based on a signal output of 50 mV.
5.0 Calibration & Adjustment
5. 1 Checking & Adjustment of Zero Output
After installation on a system, the Model 761 may require initial zero adjustment. Figure 9 shows the location of the zero adjustment potentiometer. The
access hole next to the “Z” on the label identies the Zero potentiometer.
Use a digital voltmeter with 0.0005 VDC resolution to view the signal output
of the Model 761. Adjust the signal output of the Model 761 to be 0.001 to
–0.001 V. Make this adjustment at a pressure at below the Model 761’s resolution; e.g., for a 1 Torr FS unit the zero pressure should be less than 5E-5 Torr .
The Zero potentiometer is a multi–turn potentiometer providing very ne
adjustment of the zero over a +/- 200 mV range.
Figure 9 : Location of Calibration Adjustment Potentiometers
Table 1: Recommended Lowest Pressures
Available for Reading & Pressure Control
Full Scale Range Recommended Lowest
Pressure Reading
1 Torr 5 x 10-4 Tor r 5 x 10-3 Tor r
Recommended Lowest
Pressure for Control
Use a small at bladed
screwdriver to adjust
the zero (Z). Clockwise
to increase; Counter-
clockwise to decrease
signal.
5. 2 Span (Full Scale) Adjustment and Calibration
The Zero adjustment is the only adjustment that should be made in the eld.
Span (Full Scale) and linearity adjustments require a calibrated and certied
reference standard and should only be attempted by qualied personnel. Return the Model 761 to Setra Systems for periodic calibration, Span (Full Scale)
Adjustment and Calibration adjustments and servicing. Adjusting any output
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other than zero voids the factory calibration.
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