Kistler 8840 Owner's manual

Brand: Kistler

Model: 8840

Type: Owner's manual

This manual is also suitable for

8044
8838

Instruction

Manual

K-SHEAR



Rotational

Accelerometers

Type 8838 and 8840

002-102e-06.00

(B08.8838/40e)

Pages 1... 14

B08.8838/40e-6.00

Operating Instructions

K-SHEAR

Rotational Accelerometers

Series 8838 and 8840

Instrument Corp., 75 John Glenn Drive, Amherst, NY 14228, USA

Phone (716) 691-5100, Fax (716) 691-5226, e-mail kicsales@ kistler.com

Instrumente AG Winterthur, Postfach 304, CH-8408 Winterthur, Switzerland

Phone (052) 224 11 11, Fax (052) 224 14 14, e-mail [email protected]

Types 8838/40 K-Shear Rotational Accelerometers Page 2

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Contents

Section Page

Contents............................................................................................................................................2

1. Introduction ..................................................................................................................................4

2. Important Guidelines...................................................................................................................4

2.1 For your safety................................................................................................................4

2.2 Precautions.....................................................................................................................4

2.3 Using This Manual..........................................................................................................5

2.4 K-Shear Accelerometer Types........................................................................................5

2.5 Manual Nomenclature.....................................................................................................5

3. General Description.....................................................................................................................5

3.1 Supplied Items ................................................................................................................6

4. Technical Information, Functional Description ........................................................................6

4.1 Piezoelectric Measurement Concept..............................................................................6

4.2 K-Shear Background....................................................................................................7

4.3 Low Impedance Output...................................................................................................7

5. Installation ....................................................................................................................................8

5.1 General ...........................................................................................................................8

5.2 Surface Preparation........................................................................................................8

5.3 Stud Mounting.................................................................................................................8

5.4 Direct Adhesive Mounting...............................................................................................9

5.5 Mounting with Wax……………………………………………………………………………..10

5.6 Magnetic Mounting …………………………………………………………………………….10

5.7 Summary of Mounting Methods......................................................................................11

5.8 Securing Cables..............................................................................................................12

5.9 Mass Loading Effects......................................................................................................10

6. Operation ......................................................................................................................................10

6.1 Powering.........................................................................................................................10

6.2 Ground Loops .................................................................................................................11

7. Maintenance and Calibration......................................................................................................11

7.1 General ...........................................................................................................................11

7.2 Trouble Shooting.............................................................................................................11

7.3 Repairs............................................................................................................................11

7.4 Cleaning..........................................................................................................................11

Types 8838/40 K-Shear Rotational Accelerometers Page 3

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7.5 Calibration…………………………………………………………………………….…………11

8. Accessories..................................................................................................................................12

8.1 Cable...............................................................................................................................12

9. Warranty........................................................................................................................................13

Appendix...........................................................................................................................................14

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1. Introduction By choosing Kistler K-SHEAR rotational accelerometers you have opted

for an instrument distinguished by precision, long life and technical

innovation. Please read these instructions carefully before installing and

operating these instruments.

Kistler offers a wide selection of measuring instruments and comprehensive

systems including:

• Quartz and ceramic sensors for force, pressure, acceleration,

shock, vibration and strain.

• Associated signal conditioners and accessories.

• Piezoresistive pressure transducers and transmitters with

associated amplifiers.

Kistler can also provide entire systems for special purposes in the

automotive industry, plastics processing, and biomechanics. Our general

catalog provides information on Kistler products and services. Detailed

technical data sheets are available on most products offered.

Worldwide customer service is at your disposal should you have any

questions regarding this or other Kistler products. Information on your

specific application is also available from Kistler.

2. Important Guidelines

To ensure your personal safety, please observe the safety guidelines in

this section.

2.1 For your safety

• Carefully follow the installation information contained in section 5

of this manual.

• Do not drop the instrument.

• Store in the case provided and in a clean, dry environment.

• Power the instrument in accordance with the instructions in

section 6 of this manual.

2.2 Precautions

Kistler sensors are thoroughly tested before leaving the factory. To

maintain safe and reliable operation, it is important to follow the

instructions herein.

• Do not mount accelerometers on high voltage surfaces.

• Keep cable clear of power lines and open machinery.

• Never operate or store the unit beyond the specified temperature

range.

• Do not exceed the maximum specified current.

• Never exceed the maximum specified voltage.

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• Follow the instructions for mounting. Do not over tighten.

• Do not expose the unit to excessive shock, i.e., by using a

hammer or dropping the unit.

• When not in use, store the accelerometer in the container

supplied. Always store in a clean, dry area.

• Keep the connector clean and covered when not in use

• Follow the recommendations in section 7.4

2.3 Using This Manual

Information contained herein includes a technical description, installation

and operating instructions, powering and considerations for cable length.

Section 8 contains cables available to assist with your measurement

needs.

It is recommended that the entire manual be read prior to installation and

operation of K-SHEAR rotational accelerometers. The user who has prior

experience with voltage mode piezoelectric accelerometers may want to

confine reading to particular sections of interest.

We have endeavored to arrange these instructions in a manner that

allows for easy location of topics of interest. Your Kistler representative is

also available to assist with any questions.

Information contained herein may be subject to change.

2.4 K-Shear Accelerometer Types

This manual is applicable to K-SHEARÜ rotational accelerometers listed

on the title page.

2.5 Manual Nomenclature

Throughout this manual some special designations and nomenclature are

used for specific terms and concepts relating to K-SHEAR rotational

accelerometers. These are explained in Table 1.

Term Definition

FS Full-Scale

Table 1: Manual Nomenclature

3. General Description

Kistler K-SHEAR rotational accelerometers are shear mode shock and

vibration measuring instruments. A self-generating piezoelectric sensing

element is used in conjunction with signal processing electronics that converts

the charge generated by the mechanical system into a low impedance,

voltage mode output signal. These accelerometers do not use the standard

voltage mode piezoelectric sensor couplers but are powered by any

commercially available 20 to 30 VDC power supply.

Types 8838/40 K-Shear Rotational Accelerometers Page 6

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The 8838 and 8840 differ from conventional vibration accelerometers with a

novel complement of two shear mode sensors that are designed to respond to

two distinctly different forms of rotational acceleration. Type 8838 senses

axial rotation, with the mounting screw as the axis, while the 8840 senses

lateral rotational acceleration. Unlike most accelerometers, the sensitivity of

this series is expressed these terms - μV/rad/s2.

Types 8838 and 8840 share the same appearance as shown in Figure 1.

Figure1: View of rotational accelerometers showing

center mounting hole

A center hole is intended for a cap screw mounting arrangement.

3.1 Supplied Items

Types 8838 and 8840 rotational accelerometers are designed for screw

mounting and are supplied with a 10-32 x ¾ mounting screw, M5 x 20mm

mounting screw plus this B8.8838/40e instruction manual. Optional items

are listed in the data sheet. The data sheet is shown on the Kistler

website at www.kistler.com

4. Technical Information, Functional Description

4.1 Piezoelectric Measurement Concept

Piezoelectric accelerometers convert acceleration into an electric charge.

The charge derived by the accelerometer is proportional to the force

acting on the internal quartz (piezoelectric) element. Accordingly, the

mechanical variable (acceleration) is derived from a force measurement.

4.1.1 Measurement Planes

Rotational accelerometers 8838 and 8840 share the same general

construction but differ in respective measuring planes. Type 8838

responds to oscillations occurring about the unit’s mounting axis as shown

in Figure 2.

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Figure 2: Measurement Planes for rotational

accelerometers

Type 8840 measures rotational oscillations laterally induced to its

mounting base.

4.2 K-Shear Background

The sensing assembly consists of a center post, quartz piezoelectric

crystals, seismic mass and a preload bolt. Since the unit is operated in a

shear arrangement it will sense motion perpendicular to the base. When

the accelerometer is attached to a vibrating structure, the mass exerts a

shear force on the quartz piezoelectric crystal. This applied force causes

the piezoelectric material to produce an electric charge. Since force is

mass times acceleration (from Newton's second law), the charge

produced is proportional to acceleration, since m is constant. This is

represented by:

The K-SHEAR sensing element offers many advantages over previous

shear and compression mode designs. Because of shear construction

the accelerometer is insensitive to thermal transients, transverse (cross-

axis) motion and the effects of base strain.

4.3 Low Impedance Output

Contained within the accelerometer housing is a miniature electronic

circuit. This circuit converts the high impedance charge signal generated

by the piezoelectric element into a low impedance voltage output signal

with an output impedance typically below 100 Ohms.

The low impedance output voltage provides immunity to EMI, therefore

long cable lengths can be used if necessary. All decoupling circuitry is

Types 8838/40 K-Shear Rotational Accelerometers Page 8

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internal to this design and a simple power supply of 20 to 30 Volts is all

that is required for operation. The calibration factor for these

accelerometers are given in μV/rad/s2.

A typical measuring system using the 8838 or 8840 is shown in Figure 3.

Figure 3: Diagram of an Acceleration System

1. Accelerometer

2. Optional extension cable

3. Output cable – Type 1786 or 1592M1

Optional cables are detailed in section 8.1.

5. Installation

5.1 General

For proper operation of K-SHEAR rotational accelerometers, care must be

taken during the installation process. Careful installation will result in

optimal high frequency response, accuracy and reliability.

5.2 Surface Preparation

A smooth, flat surface is necessary. If the surface is not completely flat,

the coupling between the accelerometer and the test article introduces

distortion into the measurement. A rough surface creates voids between

the mounting surfaces that reduce high frequency transmissibility.

For optimum frequency response, the surface and hole preparation

should be according to the instructions in Table 3. The roughness should

not exceed 32 microinches (0.8 micrometers).

5.3 Screw Mounting

Types 8838 and 8840 rotational accelerometers are specifically designed

for screw mounting. Socket head cap screw 431-0475-003, 10-32 x .75”

long and screw 431-0494-001, M5 x 20mm long are included with the

accelerometer and are the only screws recommended for mounting. Note

a tightening torque of 18 ±2 in-lb applies to screw mounting.

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The following guidelines should be followed when screw mounting

accelerometers.

1. Drill and tap an adequate hole to ensure a flush mount of the

accelerometer. Make sure the stud does not bottom out and

firmly secures the accelerometer. A chamfer should be machined

at the top of the mounting hole to ensure that the base of the

accelerometer makes full contact with the mounting surface

(See Table 3).

2. Completely clean the surface prior to mounting.

3. Apply a thin coat of silicon grease to both the accelerometer and

mounting surface.

4. Always use the proper sockets and a torque wrench when

installing accelerometers. Tighten the accelerometer to the torque

specified on the individually supplied calibration certificate or as

specified in Table 2. Do Not Over Tighten.

in-lbs Nm Accelerometer Types

18 ±2 2 ±0.2 8838 and 8840

Table 2: Recommended Mounting Torque

Screw D L1 inch [mm] L2 inch [mm}

431-0475-003 10-32 .16 [4.0]

.32 [8.0]

431-0494-001 M5 .16 [4.0]

.32 [8.0]

Table 3: Screw Mounting Preparation

5.4 Other Mounting Methods

Screw mounting rotational accelerometers is the only recommended

mounting method. Adhesives, wax and magnet mountings do not offer

0.0008

[0.08]

0.0004

[0.01]

32[N6]

Types 8838/40 K-Shear Rotational Accelerometers Page 10

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the necessary holding power against the impacts typically encountered

with rotational measurements.

5.8 Securing Cables

The cable to the accelerometer should be secured with the usual care

observed in good instrumentation practice. Use a radius that will not

fatigue the three conductors inside the cable. It is recommended that

cables be secured to the vibrating surface, observing the type of rotational

oscillation, to minimize cable and connector fatigue failures. Secure

cables with a cable clamp. Tape is acceptable on temporary installations.

See Section 8.5 for information on cables available from Kistler.

6. Operation

K-SHEAR rotational accelerometers are easily installed, requiring only

operational voltage. No coupler is required. A single cable is used to conduct

the operating voltage to the accelerometer electronics and to provide the

output to readout equipment.

6.1 Powering

Operating power is applied to the accelerometer or cable pin as shown in

Figure 2. The ground is common to the output signal ground. Power

requirements are 20 to 30 Volts DC at least 4mA.

Figure 4: Connector configuration showing common

ground

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6.2 Ground Loops

Types 8838 and 8840 rotational accelerometers are ground isolated,

which effectively eliminates the accelerometer from a potential ground

loop. Other components of the measuring system should inspected for

grounding paths that could establish a ground loop and associated 50-60

Hz noise.

7. Maintenance and Calibration

7.1 General

The sealed construction of K-SHEAR rotational accelerometers precludes

any internal maintenance or repairs. External cleaning is important as

covered in Section 7.4.

7.2 Trouble Shooting

Should the user experience any problems with a K-SHEAR rotational

accelerometer, the following procedure should be followed.

Check for possible intermittent cables. Faulty cables are the most

common cause of accelerometer measurement problems. The

application of a test signal at the accelerometer end of the cable is an

effective means to determine if the problem is accelerometer, cable, or

measurement instrument related.

7.3 Repairs

Field repair is not possible. Please return the accelerometer to the factory

together with a statement of problems encountered and unit serial

number. Recalibration is recommended when returning an accelerometer

to the factory. Please contact the factory and obtain a return authorization

number prior to return.

7.4 Cleaning

Clean the transducer with Isopropyl alcohol and lint-free paper wipes.

Never use air-blast to clean the connector; it may deposit a water vapor

film.

Do not us an abrasive on the base surface. This can affect the flatness

thereby reducing high frequency transmissibility.

7.5 Calibration

Calibration services are available from Kistler. Kistler acceptance test

instrumentation is in conformance with ANSI/NCSL Z-540. A calibration

certificate will be supplied showing calibration results from standards

traceable to NIST.

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8. Accessories

8.1 Cable

Types 8838 and 8840 rotational accelerometers are furnished without

cables. Optional cables are identical for both types and listed in Table 4.

Kistler Cable Type Cable Description

1578A2 Extension cable, 4-pin Microtech positive to 4-pin

Microtech negative, length is 2 meters

1578Asp Same as above except in a custom length

1592M1 Output cable, 4-pin Microtech negative to pigtails,

length is 2 meters

1786 Output cable, 4-pin Microtech negative to BNC

and banana plug pair, length is 2.6 meters

Table 4: Optional cables for rotational accelerometers

Cable Type 1786 is shown in Figure 5.

Figure 5: Configuration of output cable 1786

Call Kistler for special cable requirements.

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9. Warranty

The Kistler Instrument Corporation warrants all Kistler products to be free

from defects in material and workmanship. All such products are

warranted only under normal use and service.

For K-SHEAR triaxial, the period of warranty is 24 months from date of

shipment. For cables and adapters the warranty period is 12 months.

When returning items under warranty, said equipment shall be returned to

the Kistler Instrument Corporation prepaid. Full details relative to the claim

or malfunction shall accompany the shipment. No action will be taken

until these details are received. Please contact Kistler for a RETURN

AUTHORIZATION (RA) number before returning goods.

Settlement will be made at Kistler's discretion, either through repair or

replacement of the item in question or through issuance of full credit.

Damage occurring through misuse or mishandling, will not be covered by

this warranty.

This warranty is in lieu of all warranties expressed or implied, and of all

obligations or liabilities on the part of Kistler Instrument Corporation for

damages following the use or misuse of items supplied. Any unauthorized

disassembly or attempt at repair, shall void this warranty.

No agent or representative is authorized to assume for the Corporation

any liability except as set forth within this warranty document.

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Appendix

Specifications for Kistler accelerometers, accelerometer accessories and

many other instrumentation products are shown on the Kistler website

www.kistler.com.

This is a listing of information sheets and technical articles related to K-

SHEAR rotational accelerometer applications. Contact Kistler using the

information listed on the front cover of these instructions.

Information Sheets

Information Sheet Number Title

KI 8.002e Guidelines for Selecting an Accelerometer

Technical Article Reprints

Reprint Number Title

20.184 K-Shear Accelerometers

20.159 Lightweight Capacitive Accelerometer for Low

Frequency Measurements

K20.310 Force Limited Vibration Tests

20.148 PiezoBEAM Accelerometers: Reliable Design for

Modal Analysis

Disposal Instructions

for Electrical and Electronic Equipment

Do not discard old electronic instruments in municipal trash.

For disposal at end of life, please return this product to an

authorized local electronic waste disposal service or contact

the nearest Kistler Instrument sales office for return instruc-

tions.

Tel +41 52 224 11 11, Fax 224 14 14, info@kistler.com, www.kistler.com

This information corresponds to the current state of knowledge. Kistler reser-

ves the right to make technical changes. Liability for consequential damage

resulting from the use of Kistler products is excluded.

002-331e-09.05

Kistler 8840 Owner's manual

Brand: Kistler

Model: 8840

Type: Owner's manual

This manual is also suitable for

8044
8838

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