BRUEL & KJAER System V - Mounting and Removal of Exciter Head; 4801 Body

extra strong fle xure s, to resis t large applie d mome nt s. E nvironm e ntal testi ng of lar ge de-
vices, of unb alance d o bjects, and of objects w ith se vere t ransv erse resonances, is b est
don e with this he ad.
The
General Purpose Head Type 4812 has a 445 N (100 Ibf) force rating . The table is
larger than the 4 811 but smaller than 4813. T he moving element weight, moment limit,
and resonant freq u ency are intermediate in value between the 4811 and the 48 13 . The
Exciter Head Type 4812 is tr u ly a "Gener al Purpo s e" head, suit able for a wide ra ng e of
appl ications.
The Mode S tudy Head Type 48 14 has a 2 5 mm (1 in) pe ak -to-peak di splacement cap abil-
ity, co mpl ia nt springs a nd a light-weight mo vi ng eleme nt . T he ta bl e is ro u nd , 19 mm
(0,75 in) in diameter, with a centre insert. B oth me tr ic and in ch inse rts ar e p rovid ed.
This head is intended to be used either sing ly or in m ultiple exciter arra ys as a for ce gen-
erator . In most stru ct ural vib ration testin g ap pli ca tions , eit her a pu sh rad or a t ension
wire is connected betwee n the exc iter table top and th e te st obj e ct to mini mi ze th e c ou-
pling of skew for ce s from the test object to t he e xcit er. Ty pic al struc tur al testi ng ap plica-
t ia ns would incl ud e the det er m i natio n of th e frequ ency and damp ing for each of the reso-
nant modes of ai rcr aft elements, suc h as con troi surfa ces, wi ngs , or land in g gear. Hy-
drodynamicists and ae rodyn am icists may find t he Exc it er He ad Type 4814 use ful fo r cavi-
tation or vortex shed ding stu di es . Chemists and Chemi cal Engin eers may use this head
to vary the rate of chemic al r eactions or to vibr ate pla stic e xtru sion di es .
The Ca
libration Head Type 481 5 is design ed for the cal ibration of a ccele rom eters. A R ef-
erence St andard Acc elerome ter (included) is fi xed to a mou n ting blo ck in the ce nt re of
the table . The accelerometer to be cali br ated is sc rewed into the top of t he refe r en ce ac-
cele rometer . The skele ton of the E xciter Head Type 481 5 is sti ff , p rov id ing a reson ant
frequency of 10kHz w ithou t an attached ac ce le rom e ter , and more th an 8,5 kHz w ith
mo st types of accele ro m eters . A dequate force is pro vid ed for cali bration at l evels to
100 g at fre quen cies up to 10 kHz. Calibr at ion at l ev els as l ow as 0 , 01 g is also possi-
ble,
either by disco nnecti ng the cooling sy ste m in the 4801 or by usin g a 480 5 Exciter
Body.
3.3. MOUNTING AND REMOVAL OF EXCITER HEAD
3.3.1. 4801 Body
With the power to the Exciter Body turned off , place the Exciter Head on top of the Exci-
ter Body with the connector to t he rear (the cableto the Exciter Body is also to the rear).
The lower edge of the Head Protective Can w ill slip over the Upper Wheel of the Exciter
Body and
the Head Alignment Pins will rest on the upper s urface of th e Upper Wheel .
Rotate
the head until the Head Alignment Pins drop into the holes in the Upper Wheel
an d l ower the head until it is fully engaged . The Split Hub of the Head will provide close
concentricity guidance . Engage and press down th e Head Latche s in any order . Attach
the cable from the Power Amplifier to the connector on the Head . The Exciter is now
ready for operation.
To r emove an Exc it er Head, fi rst turn off the power swit ch on the Power Amplifier , w hich
co nt rols the power for the magneti c fi e ld of th e E xcit er. Next , dis c onne ct the ca ble from
the Exc iter Head, to e limin ate the possib ili ty of burning out the Driver Co il wh en th e Exci-
te r Head is re mov ed from the Exciter Body. Lift the Ex c iter Head ev e nl y a nd smoot hly
straight upward , being care f ul n ot to lift one side before the other . tf one side is p ulled up
before the other , it is possible to jam the head with two pins out of their holes and one
p in cocked and jammed inside its hole . If this happens , agentle tap upward with a
wooden block on the lower edge of the Head Pro tective Can or in a handle hole will re-
lease
the jammed pin . Place the head on a smooth clean surface with the table upward.
being sure that there is nothing on the surface that might d amage the Driver Co il.
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