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Содержание 4809

Страница 1: ...ibration Exciter Type 4809 The Vibration Exciter Type 4809 is a permanent magnet type exciter for use in accelerometer calibration mechanical impedance measurement or testing of small structures It has a force rating of 10 lbf 44 5 N ...

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Страница 3: ...VIBRATION EXCITER TYPE 4809 May 1972 ...

Страница 4: ...Inserts 6 2 4 Additional Cooling 7 2 5 Positioning the Exciter 7 2 6 Pushrods 9 3 CHARACTERISTICS 11 3 1 Frequency Response and Resonance 11 3 2 Rated Force and Limits 11 3 3 Cross Motion 13 4 APPLICATIONS 14 4 1 Accelerometer Calibration 14 4 2 Mechanical Impedance 15 4 3 Force Controlled Testing 16 5 SPECIFICATIONS 18 ...

Страница 5: ... object It can be operated in any position The Type 4809 can be used for accelerometer calibration for mechanical impedance measurements for educational demonstrations or for vibration testing of small objects or structures It has a maximum acceleration capacity of 75 g and a maximum displace ment of 0 315 in 8 mm peak to peak Low distortion operation is possible in the frequency range 20 Hz to 20...

Страница 6: ...coil B the flux density of the magnetic field and F the force generated by the coil The magnitude of the force is given by F where F B I L BIL Force in Newtons Magnetic flux in Gauss Current in coil Amperes Length of conductor in magnetic field meters The current for the exciter is provided by a power amplifier A signal source such as a sine wave oscillator or random generator is connected to the ...

Страница 7: ...4 5 Newton The moving element weight is 0 132 lb 60 gm If the test object weights 0 37 lb 170 kg the maximum accele ration with this load is a 2 2 DESCRIPTION W We F 0 13 0 37 20 10 g Fig 2 2 shows a sectional drawing of the Type 4809 The magnetic field 8 mentioned in section 2 1 is here supplied by a permanent magnet which projects up into the space enclosed by the driver coil A cast iron magneti...

Страница 8: ...to 0 315 inches 8 mm These are intended for emer gency use to protect the Exciter and the test specimen If the moving element hits these stops there is a clearly audible bumping sound and the signal waveform from any transducer mounted on the Exciter will be distor ted The level of acceleration should be reduced at once 3 REPLACEABLEINSERTS The Exciter is provided with 5 inserts a bottle of thread...

Страница 9: ...n the cement before unscrewing 2 4 ADDITIONAL COOLING Under normal operation up to its rated current of 5 Amperes the 4809 can operate continuously without overheating However since the table is an integral part of the moving element skeleton its temperature can increase considerably under full load conditions If the specimen is temperature sensitive this could have some effect on the test For ins...

Страница 10: ... for the forced air openings have a groove cut into them see Fig 2 3 to facilitate the suspension of the Exciter by cables or other hangers The plugs are located along a line passing through the center of gravity of the instrument 272125 Fig 2 4 Stand for using Type 4809 in horizontal position 8 ...

Страница 11: ...ents result in bending of the rod rather than rubbing of the driver coil Fig 2 5 shows a sketch of a pushrod for use with the Type 4809 Exciter The two halves are screwed tight to the Exciter table and the object then locked together by means of four center screws 5 mm Steel Rod Silver Solder 10 32 UNF I __j J Rt 29 5mm M3 Screws c_l0 32 UNF Fig 2 5 Pushrod for use with the Type 4809 Fig 2 6 shows...

Страница 12: ...272124 Fig 2 6 Horizontal vibration fixture with Type 4809 built in 10 ...

Страница 13: ... by dB dB 860 2 15 0 0 500 1000 2000 5000 10000 20000 40000 D A B C Un Zero level 1612 2112 A B C Lin Fig 3 1 Frequency response of the Type 4809 The acceleration level increases with frequency to a damped peak at about 150 Hz This is the suspension resonance of the Exciter The acceler ation level then remains constant from 700 to 5000 Hz after which it climbs sharply to a peak at 16 kHz This peak...

Страница 14: ...ad 30 8 gram 0 068 lb 9 J _ I l I l 30 g 294 m s2 Payload 91 6 gram 0 20 lb ff r 11 20 g 196 m s2 Payload 170 gram 0 37 lb I I I I I I t to R 10 g 98 1 m s2 Payload 394 gram 0 87 lb S J I l l l l l CY 5 g 49 m s2 Payload 850 gram 1 87 lb v 1 10 Hz 20 50 100 200 500 1 kHz 2 5 10 20 Frequency 271061 Fig 3 2 Load rating curves for the Type 4809 _ K lc r BrUel Kjcar u l KJao ij Kfao a Potontlom 0 0 50...

Страница 15: ...ng any error to the calibration The cross motion of the Type 4809 is very low as can be seen in Fig 3 3 where cross motion expressed as a percentage of the axial motion is plotted against frequency for an acceleration level of 50 g RMS Except for a few isolated peaks the cross motion is well below 1 throughout the frequency range of the Type 4809 13 ...

Страница 16: ... setup using the Type 2970 Sensitivity Com parator Conditioning Amplifier 2626 Sine Random Generator Type 1024 _ Standard Accelerometer Signal Control Power Amplifier 2706 Conditioning Amplifier 2626 __ f lo l l i Conditioned Unknown Signal Level Recorder 2305 a J 0 I _ I I Vibration Exciter 4809 272 i Fig 4 1 Accelerometer Calibration The signal from the Standard Accelerometer is used to control ...

Страница 17: ...always necessary to consider this phase difference when making measurements The numerical value of mechanical impedance is often all that is required and since Z is pro portional to 0 a plot of mechanical impedance can be obtained by holding the velocity constant and varying the frequency Fig 4 2 shows the basic setup for measuring the numerical value of mechanical impedance The signal from the Be...

Страница 18: ...p lif ier 2 62 3 4 Fig 4 2 Mechanical Impedance measurement 4 3 FORCE CONTROLLED TESTING 27 Zt 1 6 For structural testing it is the general rule to control the Exciter with a force controlled compressor loop such as that shown in Fig 4 3 16 Exciter 4809 Force Transducer 8200 Fig 4 3 Force controlled structural test Z721Z ...

Страница 19: ...ss of table and specimen resonances provided suitable com pressor speeds and sweep speeds are selected The Force Transducer Type 8200 has a nominal charge sensitivity of 17 8 pC Ibf 4 pC N While there are no direct reading force scales for the Measuring Amplifier a proper choice of acceleration scales will accomplish the same purpose The SA 0071 scale is for accelerometers with a sensitivity of 6 ...

Страница 20: ...hown on Fig 3 2 75 g 736 m s2 5 Amp RMS 0 315 in 8 mm peak to peak 65 in s 1 65 m s peak Moving Element Dynamic Weight 0 132 lb 60 gm Resonance Frequency Unloaded Table 20 kHz Stray Magnetic Field 20 X 1o 3 Weber m2 at table surface MechanicaiFuselnserts 10 32 UNF center insert in 1 16 in 29 5 mm diameter table Cross Motion less than 3 of the axial motion to 15kHz Dynamic Flexure Stiffness 112 4 l...

Страница 21: ...ht ACCESSORIES SUPPLIED 5 X YS 0811 1 X QA 0029 1 x QA 0061 1 bottle as 0003 18 3 lb 8 3 kg 10 32 UNF inserts Screw tap for 10 32 UNF thread Insert mounting tool Thread locking cement LOCTITE screw lock 19 ...

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Страница 24: ...ucers Impedance Heads Accelerometer Preamplifiers Vibration Meters Accelerometer Calibrators Magnetic Transducers Capacitive Transducers Complex Modulus Apparatus VIBRATION TESTING Exciter Controls Sine Exciter Controls Sine Random Exciter Equalizers Random or Shock Exciters Power Amplifiers Programmer Units Stroboscopes STRAIN MEASUREMENTS Strain Gauge Apparatus Multi point Panels Automatic Selec...

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