PCB Piezotronics 3711D1FA20G User manual

Model 3711D1FA20G
DC Accelerometer
Installation and Operating Manual
For assistance with the operation of this product,
contact PCB Piezotronics, Inc.
Toll-free: 800-828-8840
24-hour SensorLine: 716-684-0001
Fax: [phone]
E-mail: [email protected]
Web: www.pcb.com

The information contained in this document supersedes all similar information that
may be found elsewhere in this manual.
Total Customer Satisfaction – PCB
Piezotronics guarantees Total Customer
Satisfaction. If, at any time, for any
reason, you are not completely satisfied
with any PCB product, PCB will repair,
replace, or exchange it at no charge. You
may also choose to have your purchase
price refunded in lieu of the repair,
replacement, or exchange of the product.
Service – Due to the sophisticated nature
of the sensors and associated
instrumentation provided by PCB
Piezotronics, user servicing or repair is
not recommended and, if attempted, may
void the factory warranty. Routine
maintenance, such as the cleaning of
electrical connectors, housings, and
mounting surfaces with solutions and
techniques that will not harm the
physical material of construction, is
acceptable. Caution should be observed
to insure that liquids are not permitted to
migrate into devices that are not
hermetically sealed. Such devices should
only be wiped with a dampened cloth
and never submerged or have liquids
poured upon them.
Repair – In the event that equipment
becomes damaged or ceases to operate,
arrangements should be made to return
the equipment to PCB Piezotronics for
repair. User servicing or repair is not
recommended and, if attempted, may
void the factory warranty.
Calibration – Routine calibration of
sensors and associated instrumentation is
recommended as this helps build
confidence in measurement accuracy and
acquired data. Equipment calibration
cycles are typically established by the
users own quality regimen. When in
doubt about a calibration cycle, a good
“rule of thumb” is to recalibrate on an
annual basis. It is also good practice to
recalibrate after exposure to any severe
temperature extreme, shock, load, or
other environmental influence, or prior
to any critical test.
PCB Piezotronics maintains an ISO-
9001 certified metrology laboratory and
offers calibration services, which are
accredited by A2LA to ISO/IEC 17025,
with full traceablility to N.I.S.T. In
addition to the normally supplied
calibration, special testing is also
available, such as: sensitivity at elevated
or cryogenic temperatures, phase
response, extended high or low
frequency response, extended range, leak
testing, hydrostatic pressure testing, and
others. For information on standard
recalibration services or special testing,
contact your local PCB Piezotronics
distributor, sales representative, or
factory customer service representative.
Returning Equipment – Following
these procedures will insure that your
returned materials are handled in the
most expedient manner. Before returning
any equipment to PCB Piezotronics,
contact your local distributor, sales
representative, or factory customer
service representative to obtain a Return
Warranty, Service, Repair, and
Return Policies and Instructions

Materials Authorization (RMA)
Number. This RMA number should be
clearly marked on the outside of all
package(s) and on the packing list(s)
accompanying the shipment. A detailed
account of the nature of the problem(s)
being experienced with the equipment
should also be included inside the
package(s) containing any returned
materials.
A Purchase Order, included with the
returned materials, will expedite the
turn-around of serviced equipment. It is
recommended to include authorization
on the Purchase Order for PCB to
proceed with any repairs, as long as they
do not exceed 50% of the replacement
cost of the returned item(s). PCB will
provide a price quotation or replacement
recommendation for any item whose
repair costs would exceed 50% of
replacement cost, or any item that is not
economically feasible to repair. For
routine calibration services, the Purchase
Order should include authorization to
proceed and return at current pricing,
which can be obtained from a factory
customer service representative.
Warranty – All equipment and repair
services provided by PCB Piezotronics,
Inc. are covered by a limited warranty
against defective material and
workmanship for a period of one year
from date of original purchase. Contact
PCB for a complete statement of our
warranty. Expendable items, such as
batteries and mounting hardware, are not
covered by warranty. Mechanical
damage to equipment due to improper
use is not covered by warranty.
Electronic circuitry failure caused by the
introduction of unregulated or improper
excitation power or electrostatic
discharge is not covered by warranty.
Contact Information – International
customers should direct all inquiries to
their local distributor or sales office. A
complete list of distributors and offices
can be found at www.pcb.com.
Customers within the United States may
contact their local sales representative or
a factory customer service
representative. A complete list of sales
representatives can be found at
www.pcb.com. Toll-free telephone
numbers for a factory customer service
representative, in the division
responsible for this product, can be
found on the title page at the front of this
manual. Our ship to address and general
contact numbers are:
PCB Piezotronics, Inc.
3425 Walden Ave.
Depew, NY 14043 USA
Toll-free: [phone]
24-hour SensorLineSM: [phone]
Website: www.pcb.com
E-mail: [email protected]
DOCUMENT NUMBER: 21354
DOCUMENT REVISION: B
ECN: 17900

Manual Number: 32650
Manual Revision: C
ECR Number: 36283
3710 series DC Accelerometer Operating Guide
1
1.0 Introduction
This operating guide contains information that will familiarize
the user with the basic operation and installation of the 3710
Series MEMS DC Accelerometers. However, it is not
intended to cover all of the specific measurement challenges
that one may encounter while using the device. Therefore, if
you have detailed questions or are unsure of how to properly
operate the sensor after reading this “Operating Guide”, please
contact a PCB Application Engineer using our 24-Hour
SensorLine
TM
at 716-684-0001.
2.0 Common Applications and Features
The 3710 Series MEMS DC Accelerometers achieve true DC
response for measuring uniform (or constant) acceleration and
low-frequency vibration. For this reason, they are often used
to:
•Perform ride quality assessments of elevators,
automobiles, trains, and amusement park rides.
•Analyze the low frequency characteristics of buildings,
bridges, and large aerospace objects.
•Acquire tilt and orientation data for feedback control and
stabilization purposes.
Because of the critical nature of these and similar test
applications, all 3710 series MEMS DC Accelerometers have
been designed and manufactured with the following common
characteristics:
•Rugged, all-welded titanium housing insures reliability
and durability in demanding applications and environ-
ments.
•Built-in microelectronics provide conveniently standard-
ized sensitivities and low-noise output signals unmatched
by similar sensing technologies.
•Internal voltage regulator allows sensor to be powered
from virtually any unregulated DC voltage source, such as
a bench-top power supply or portable battery source.
•Gas damping extends the upper frequency range, atten-
uates unwanted high-frequency vibration, and provides
stable performance over the entire operating temperature
range.
•Hermetic, multi-pin connector provides a reliable connec-
tion even under the harshest environmental conditions.
3.0 Principle of Operation
The sensor element of the 3710 series features a proof mass,
ring frame, and attachment system between the two. These
features are bulk micro machined from the same single-crystal
silicon wafer. The movement of the proof mass is directly
affected by acceleration applied in the axis of sensitivity.
The sensor element is connected as a bridge element in the
circuit. The electrical characteristics of one portion of the
bridge, increases in value, while the other decreases when
exposed to acceleration. This approach minimizes common
mode errors and improves non-linearity.
A selection of full scale measurement ranges are attained by
modifying the stiffness of the suspension system of the proof
mass. A high natural frequency is accomplished through the
combination of a lightweight proof mass and suspension stiff-
ness.
Ruggedness is enhanced through the use of mechanical stops
on the two outer wafers to restrict the travel of the proof mass.
Damping is used to mitigate high frequency inputs.
The sensor elements use squeeze-film gas damping that is
nominally 0.7 critical. This is the result of the movement of the
proof mass pressing on the gas in the gap between it and the
outer sensor layer. Damping helps prevent the output of the
accelerometer from becoming saturated, as would happen
when the resonance of an accelerometer with no damping is
excited by random vibration. The advantage of gas damping
over liquid damping is that it is minimally affected by tem-
perature changes.
The 3710 series accelerometers contain conditioning circuitry
that provides a high sensitivity output. This IC also provides
compensation of zero bias and sensitivity errors over tempera-
ture using a continuous piecewise straight line correction en-
gine.
An on-board voltage regulator allows a typical excitation
range of 6 to 30 VDC with <10 mA current draw. The 3710
series features a ± 2 V Full Scale zero based output referenced
to power ground. A negative voltage generator provides a
sufficient signal swing for negative acceleration outputs with a
positive voltage swing of +4.0 V accommodating positive
accelerations.
An automated calibration step is conducted at the completion
of the accelerometer assembly at discrete temperatures over
the specified operating temperature range. The IC features an
on-chip temperature sensor for accurate thermal corrections.

Manual Number: 32650
Manual Revision: C
ECR Number: 36283
3710 series DC Accelerometer Operating Guide
2
4.0 Typical Measurement System
The 3710 series DC Accelerometers are available in a uniaxial
or triaxial package, with the triaxial model being the 3713
version. The output signal is routed to follow-on signal condi-
tioning via a hermetic four-pin receptacle and associated cable
assembly, Model 010 series for the 3711 uniaxial version, and
Model 037 series nine-pin cable assembly, for the 3713 triax-
ial version. Since the High Sensitivity DC Accelerometers
contain a built-in voltage regulator, they may be powered from
virtually any 6 to 30 Vdc power source without adversely af-
fecting sensor performance. PCB signal conditioners available
are Model 445B01, a single-channel, line powered, signal
conditioner for the uniaxial 3711series DC accelerometers and
Model 478A05, a three-channel, line-powered signal con-
ditioner for the triaxial 3713 accelerometer. Consult PCB
Application Engineering for additional signal conditioning
options. The output from the signal conditioner is typically
routed to readout instrumentation such as oscilloscopes or
various model data acquisition instruments.
5.0 Sensor Installation
When choosing an installation technique, be certain to care-
fully examine the different application characteristics that may
affect sensor performance. Characteristics such as mounting
location may limit the use of large mounting blocks or the
amplitude range may necessitate the use of a stud mount rather
than using adhesive. A summary of the recommended
mounting methods is provided below.
Stud Mount: Recommended for permanent mount applica-
tions or in test situations that require a rugged or secure install-
lation. The necessary information, including surface finish,
mounting hole dimensions, and recommended mounting torque
for installing the sensor is listed on the enclosed Sensor
Installation Drawing. It is recommended that an experienced
technician or machinist with good machining capabilities ade-
quately prepare the surface.
Adhesive Mount: Recommended for temporary mounting of
the sensor or when the test object surface cannot be properly
prepared for stud mounting. Wax works well for temporary
mount applications under conditions where the operating tem-
perature will not melt the wax or the acceleration levels will
not dislodge the sensor from the test object. Cyanoacrylate-
based, “quick-bonding” adhesives provide a quick mounting
method, while two-part epoxies can be used for a more secure
mount. To remove an adhesively mounted sensor, it is best to
place an open-ended wrench over the sensor and twist it to
shear the adhesive bond. Striking the sensor with a hammer or
other object may permanently damage the sensor.
Easy Mount Clip: Recommended when frequent installation
and removal of Series 3710 series accelerometers is desired.
The Easy-Mount Clip can either be stud mounted or adhe-
sively mounted to the test structure. (If adhesively mounting
the clip, detach the sensor from the clip first, as excessive ad-
hesive may creep through the mounting holes and adhere to the
sensor. This will make separation and removal from the clip
difficult.) Once the Easy-Mount Clip has been attached to the
test structure, the sensor can be easily snapped into and out of
the clip. Over time, the Easy-Mount Clip must be replaced as
it will “wear-out” and eventually lose its ability to securely
hold the sensor.
6.0 Powering
The 3710 Series contains built-in microelectronics that will
operate from any PCB Series 445 or Series 478 Sensor Signal
Conditioner. These signal conditioners provide the necessary
voltage and current required for all of the powering options
available on the 3710 series.
The 3710 series may also be powered by other voltage sources
such as DC voltage laboratory supplies, automotive or marine
batteries, or low-voltage supplies designed for powering PC
Board components. If you decide to not use a Series 445 or
478 Series Signal Conditioner, insure that the source provides
power within the excitation voltage range listed on the specifi-
cation sheet for that model. It is important to note that since
the accelerometers contain a built-in voltage regulator, precise
calibration of the power source is generally not required.
7.0 Operation
After the sensor has been installed and the cable connected for
proper operation, there are a couple of measurement points to
take note of:
•To take advantage of the DC response of the accelerome-
ter, the readout device must be in a DC coupled state.
Consult the appropriate manufacturer or product manual
for your readout device for details.
•Because the 3710 series can measure static (constant)
accelerations, the DC offset voltage will be affected by the
positional alignment relative to the Earth’s gravity. In
other words, when the sensor is mounted perpendicular
with the Earth’s surface, the offset will equal that as
specified on the calibration certificate for “zero-g offset
voltage.” If the sensor is mounted parallel with the
Earth’s surface, the sensor will be experiencing 1 g of ac-
celeration and the offset voltage will increase by the sen-
sitivity of the accelerometer.

Manual Number: 32650
Manual Revision: C
ECR Number: 36283
3710 series DC Accelerometer Operating Guide
3
•If the sensor is extended, in the case of an integral cable
sensor, or a cable length other than 10ft is used, in the
case of sensor with an integral connector, the offset
voltage will change. To determine the accelerometer’s
offset, rotate the unit 90° so that the sensor is on its side
with the sensing axis perpendicular to Earth’s gravity and
record the DC output. This value is the new “zero-g off-
set voltage.”
•To insure that ground loops are not induced, the shield
should only be terminated at one end. Typically, the shield
of the cable is tied to sensor housing. If the sensor is
mounted with an isolation pad (or other form of electrical
isolation) from the test structure, then the shield should be
tied to signal ground at the instrumentation end.
Otherwise, leave the cable shield floating or not connected
at the instrumentation end.
8.0 Sensor Verification
If the sensor has been handled in a rough manner or before a
critical measurement application, it is a good idea to verify that
the sensor’s sensitivity is still within specification. An
accurate static calibration of the 3710 series can be performed
using the Earth’s Gravitational Field as a reference. The sen-
sor can simply be “flipped” (rotated 180°) in the Earth’s Grav-
ity to obtain the scaling factor (sensitivity) and DC offset.
First, place the accelerometer in a +1g orientation so that the
base is resting on the table and the model number is facing up.
The sensing axis will be parallel with the Earth’s gravity with
the sensor experiencing +1g acceleration. Record the DC
output by using a DVM. Then rotate the sensor 180° so that
the sensor is inverted (the top of the sensor is resting on the
table) and the sensor is experiencing –1g acceleration. Record
the DC output.. To calculate the sensitivity of the acceler-
ometer refer to equation 8.1.
Sensititvity = (+1g) – (-1g) Eq 8.1
2
9.0 Sensor Calibration
Due to ISO 9001, ISO Guide 25, or other contractual require-
ments, it may become necessary to send the accelerometer
back to PCB for recalibration. In this case, a complete back-
to-back frequency response test will be performed and the
“zero-g” offset voltage will be checked with NIST traceable
equipment.
10.0 Maintenance and Repair
Because of the sophisticated nature of PCB instrumentation,
field repair of the equipment is not recommended. Most PCB
sensors are of modular construction and are factory repairable.
A repair or replacement quotation is available at no charge.
Before returning equipment for repair, it is recommended that
the user confer with a factory application engineer (or inter-
national representative) to first troubleshoot the problem.
11.0 Return Procedure
To expedite the repair process, contact a factory application
engineer to obtain a Return Material Authorization (RMA)
number prior to sending equipment to the factory. Please have
information, such as model number, serial number and de-
scription of the problem, available.
Customers outside the U.S. should consult their local PCB
distributor for information on returning equipment. For ex-
ceptions to this guideline, please contact the International
Sales department to request shipping instructions and an RMA.
For further assistance, please call [phone] or fax us at
[phone]. You may also receive assistance via e-mail at
[email protected]m or visit our web site at www.pcb.com.
12.0 Customer Service / Warranty
The employees of PCB strive to provide superior, unmatched
customer service. Should you at any time find yourself dissat-
isfied with any PCB product for any reason, consult a factory
Application Engineer or local representative/distributor to
discuss repair, refund, or exchange procedures.
When unexpected measurement problems arise, call our 24-
hour Sensor Line
TM
at [phone] to discuss your
immediate dynamic instrumentation needs with a Factory
Representative.