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The sensor selects the guide
Sensor type choice
Piezoelectricity type sensor sensitive core body
material and structural style
Piezoelectricity type acceleration instrument signal
output form
Sensor sensitivity, measuring range and frequency range
choice
Sensor whole seal design and electric cable
The external environment to surveys the sensor the
influence
The project vibration size physical parameter commonly
used displacement, the speed and the acceleration expressed. As
a result of is very small in the usual frequency range 内振?
displacement peak-to-peak value quantity, also between the
displacement, the speed and the acceleration all may mutually
transform, therefore inspires the momentum in the actual use the size
generally to measure with the acceleration value. The commonly
used unit is: Rice/second 2 (m/s2), or gravity acceleration (g).
The description vibration signal another important parameter is
the signal frequency. The overwhelming majority project
vibration signal decomposable becomes a series of spot frequencies and
the peak-to-peak value sine signal, therefore, to some vibration
signal survey, is in fact to composes this vibration signal the sine
frequency component survey. Also is surveys the peak-to-peak
value precision to the sensor main performance index inspection
according to the sensor in its stipulation frequency range the height
to evaluate.
The most commonly used oscillator measurement sensor may divide
into the piezoelectricity type, the pressure according to respective
principle of work anti-, the electric capacity type, the inductance
type as well as the photoelectricity type. The piezoelectricity
type acceleration instrument because has the survey frequency range
width, the measuring range in a big way, the volume small, the weight
light, to was measured a influence is small as well as installs the
easy to operate, therefore becomes the most commonly used oscillator
measurement sensor.
• Sensor type choice.
O piezoelectricity type - principle and
characteristic
The piezoelectricity type sensor uses the spring quality
system principle. After the sensitive core body quality is
vibrated the acceleration function to produce to become with the
acceleration the direct ratio the strength, after the piezoelectricity
material is formed this action of force along its surface with this
strength becomes the direct ratio the electric charge signal.
The piezoelectricity type acceleration instrument has the
dynamirange big, the frequency range width, firm durable, is been
small as well as the piezoelectricity material stress the external
interference from produces the electric charge signal not to need
characteristic and so on any outside power source, is by the most
widespread use oscillator measurement sensor. Although
piezoelectricity type acceleration instrument structure simple,
商业?use history also very long, but because its performance
index and materials behavior, design and processing craft close
correlation, therefore sells in the market the similar sensor
performance actual parameter is extremely big by and its the stability
and the uniform difference. With presses anti- and the electric
capacity type compares, its biggest shortcoming is the
piezoelectricity type acceleration instrument cannot survey the zero
frequency rate signal.
O presses anti- -like
Should the live pressure anti- acceleration instrument
sensitive core body make the measure of resistance electric bridge for
the semiconducting material, its structure dynamic model still was the
spring quality system. The modern micro processing manufacture
technology development causes to press the anti- form sensitive core
body the design to have the very big flexibility to suit each kind of
different survey request. In the sensitivity and the measuring
range aspect, from the low sensitivity high measuring range impact
survey, all have the pressure anti- form to the direct current high
sensitivity low frequency survey the acceleration instrument.
Simultaneously presses the anti- acceleration instrument survey
frequency range also to be possible to have the rigidity from the
direct current signal to be high, survey frequency range to several
dozens kilohertz high frequency surveys. The
microminiaturization design also is presses the anti- sensor a
luminescent spot. Needs to point out is the completely pipe
pressure anti- sensitive core body design and the application has the
very big flexibility, but its use scope speaking of some specific
design pressure anti- core body generally to have to be smaller than
the piezoelectricity sensor. Presses the anti- acceleration
instrument another shortcoming is been bigger the temperature
influence, the practical sensor generally all needs to carry on
temperature compensation. In the price aspect, mass use pressure
anti- sensor 成本?has the very big market competition strength,
but will create to the special use sensitive core system this far is
higher than the piezoelectricity acceleration instrument.
O electric capacity type
The electric capacity acceleration instrument structural
style generally also uses the spring quality system. When the
quality is changed the acceleration function movement the nature
量块 then to cause with the fixed electrode between gap 电容?
the change. The electric capacity type accelerometer compares
with other types acceleration instruments has the sensitivity high,
the zero frequency response, the environment compatibility good and so
on the characteristic, receives the temperature the influence quite to
be small in particular; But the deficiency displays in the
signal input-output is the non-linearity, the measuring range is
limited, the electric cable electric capacity influence, as well as
electric capacity sensor itself is the high impedance supply
oscillator, therefore the electric capacity sensor output signal often
must give through the successor electric circuit to the improvement.
The electric capacity type acceleration instrument more uses in
the low frequency survey in the practical application, its versatility
was inferior to the piezoelectricity type acceleration instrument,
also the cost also is much higher than the piezoelectricity type
acceleration instrument.
• Piezoelectricity type sensor sensitive core
body material and structural style
O piezoelectricity material
The piezoelectricity material generally may divide into
two big kinds, namely piezoelectric crystal and piezoelectricity
ceramics. In the piezoelectricity accelerometer most commonly
used piezoelectric crystal is the quartz, its characteristic for
operating temperature scope wide, the performance is stable, therefore
frequently serves as in the practical application the standard sensor
the piezoelectricity material. Is much lower than as a result of
the quartz piezoelectric modulus other piezoelectricity materials,
therefore the more commonly used piezoelectricity material speaking of
the general piezoelectricity accelerometer for the piezoelectricity
ceramics. In the piezoelectricity ceramics the zirconium titanic
acid lead (PZT) is the piezoelectricity material which in the present
piezoelectricity accelerometer frequently uses. Its
characteristic for has the higher piezoelectric modulus and the Curie
temperature, each mechanical and electrical parameter relative is
smaller along with the temperature time substandard condition change.
Must point out, speaking of the identical variety
piezoelectricity ceramics, although all has the same basic
characteristic, but because the manufacture craft different may cause
two same materials the piezoelectricity ceramics concrete performance
index difference to be really big. This kind of phenomenon may
and imports the sensor through the model domestically produced sensor
the comparison to be able to reflect that, the domestic vibration test
industry several dozens years experience regarding this 深有体会.
O sensor sensitive core body structural style
The piezoelectricity acceleration instrument sensitive
core body generally 量块 is composed by the piezoelectricity
material and the attachment nature, after the nature 量块 receives
the acceleration function then to transform to have the direct ratio
with the acceleration and increase to the piezoelectricity material on
the strength, after but the piezoelectricity material stress produces
in its surface to have the direct ratio with the acceleration the
electric charge signal. The piezoelectricity material
characteristic had decided the action may be the stress may also be
the shearing stress, the electric charge size which the
piezoelectricity material produces draws out along with the action
direction as well as the electric charge superficial the position to
change. According to the piezoelectricity material different
stress method, the commonly used sensor sensitive core body structure
generally has following three kind of forms:
The compression form ¨C piezoelectricity
material receives the compression or the stretch strength has the
electric charge structural style. The compression type sensitive
core body is in the acceleration instrument the traditional structural
style. Its characteristic is makes simply is convenient, can
have the higher 自振 resonance frequency and the wider frequency
measurement scope. But the biggest shortcoming is cannot
effectively remove each kind of disturbance to survey the signal the
influence.
Cuts the form ¨C through to exert the
shearing force to the piezoelectricity material to have the electric
charge structural style. Theoretically analyzes the electric
charge signal which the piezoelectricity material produces under the
shearing force function the external interference influence to be
really small, therefore cuts the structural style to become the most
widespread use the acceleration instrument sensitive core body.
However in the actual manufacture process, guarantees cuts the
sensitive core body the accelerometer to have higher and the stable
frequency measurement scope actually is in the sensor manufacture in
the craft a most difficult link. North wisdom BW-Sensor uses the
import memory metal material the fastener thus to guarantee the sensor
has the stable reliable resonance frequency and the frequency
measurement scope.
The bending strain Liang form -
piezoelectricity material receives the bending strain to have the
electric charge structural style. The bending strain Liang
structure may produce the quite big electric charge output signal,
also is easier to realize the control damping; But because its
survey frequency range low, because this structure cannot remove
because of the signal drifting which the temperature change but is
extremely easy to produce, therefore this structure is short very much
in the piezoelectricity accelerometer design is used.
• Piezoelectricity type acceleration
instrument signal output form
O electric charge output
The traditional piezoelectricity accelerometer outputs
through the internal sensitive core body to have the direct ratio with
the acceleration the electric charge signal. In the actual use
the sensor outputs the high impedance electric charge signal must
transform through two measuring appliances it the low bucking voltage
signal to be able to read takes. Because the high impedance
electric charge signal is extremely easy to receive the disturbance,
therefore must use the low noise shielded cable the sensor to two
measuring appliances between signalling. Because the electronic
device application temperature scope is limited, therefore under high
temperature environment survey generally or use electric charge
output. North wisdom BW-Sensor uses imports ceramic the
accelerometer to be possible to use for a long time in the temperature
-40oC~250oC scope.
O low bucking voltage output (IEPE)
The IEPE piezoelectricity accelerometer namely usually
called ICP piezoelectricity accelerometer. The piezoelectric
pick-up transducer outputs the electric charge transforms the low
impedance through the attire in the sensor interior pre-amplifier the
voltage output. The IEPE sensor usually is two outputs forms,
namely uses the continuous current 电压?power supply;
Direct current power supply and signal use identical root line.
The usual direct current partially through high passes the
filter in the continuous current power source out-port to filter out.
The IEPE sensor biggest merit is surveys the signal quality
good, the noise small, the anti- external interference ability strong
and the telemetering, specially the new number picks the system very
much to provide 恒流 电压? therefore, the IEPE sensor can pick
the system with the number directly to be connected but does not need
any other two measuring appliances. The IEPE sensor has
gradually substituted for traditional in the vibration test the
electric charge output piezoelectricity accelerometer.
• Sensor sensitivity, measuring range and
frequency range choice
The piezoelectricity pattern accelerometer is vibrates
the test the most main sensor. Although piezoelectricity
accelerometer survey scope wide, but because in the market this kind
of accelerometer variety is many, therefore for correct selects brings
the certain difficulty. As selects the oscillationpick-up the
principle of equality: Correct selects should based on to survey
the signal following three aspects the analysis and the estimate.
O was measured inspires the momentum the size
O is measured the vibration signal the
frequency range
The o vibration tests the scene
environment
Below will aim at above three aspects and refers to the
sensor the related technical specification to concrete to select does
further discusses
According to was measured inspires the momentum the size
acceleration survey scope and the sensitivity choice
• Sensor sensitivity and measuring
range scope
The sensor sensitivity is one of sensor most basic
quotas. The sensitivity size directly affects to the sensor to
vibrates the signal the survey. Is not difficult to understand
that, the sensor sensitivity should act according to was measured
inspires the momentum (acceleration value) the size to decide, but
because the piezoelectricity acceleration instrument is surveys the
vibration the acceleration value, but acceleration value and the
signal frequency square has the direct ratio under the same
displacement peak-to-peak value condition, therefore the different
frequency band acceleration signal size difference is really big.
The large-scale structure low frequency vibrates it to inspire
the momentum the acceleration value possibly to be able to be quite
small, for example works as the vibration displacement is 1mm, the
frequency is 1 Hz signal its acceleration value only is 0.04m/s2
(0.004g); However to the high frequency vibration works as the
displacement is 0.1mm, the frequency is 10 kHz signal its acceleration
value may reach 4 x 10 5m/s2 (40000g). Therefore although the
piezoelectricity type acceleration instrument has the bigger survey
measuring range scope, but to uses in to survey the height beginnings
and ends frequency the vibration signal, the choice acceleration
instrument keen degree-hour should have the full estimate to the
signal. The most commonly used oscillator measurement
piezoelectricity type accelerometer sensitivity, the voltage output
(IEPE) is 50~100 mV/g, the electric charge output is 10 ~ 50 pC/g.
The acceleration value sensor survey measuring range scope is
refers to the sensor the greatest observed value which can survey in
the certain non-linear erroneous scope. The general
piezoelectricity acceleration instrument non-linear error mostly is
1%. As the principle of equality, keenly goes past the high its
survey scope smaller, otherwise keenly goes past slightly surveys the
scope to be bigger.
The IEPE voltage output piezoelectricity acceleration instrument
survey scope is by the maximum output signal electricity 压所
decision which permits in the miss distance scope, the maximum output
voltage size generally all for ±5V. May obtain the sensor
through the conversion the greatest measuring range, namely is equal
to the maximum output voltage and the sensitivity ratio. Needs
to point out is the IEPE piezoelectric pick-up measuring range besides
receives the non-linear erroneous size influence, but also receives
the power line voltage and the sensor bias voltage restriction.
When when the power line voltage and the bias voltage bad value
is smaller than the measuring range voltage which the sensor technical
specification produces, the sensor maximum output signal can have the
distortion. Therefore IEPE acceleration instrument bias voltage
regulation or not not only affects the low frequency survey also
possibly can cause the signal distortion; This kind of
phenomenon when high cryogenic measurement needs specially to pay
attention, when sensor in sets at the electric circuit when the non-
room temperature condition unstable, the sensor bias voltage is very
possible unceasingly slowly to drift creates the survey signal greatly
suddenly to be suddenly small.
But the electric charge output survey scope receives the sensor
mechanical rigidity the restriction, 传感 the sensitive core body
must be much bigger than under the similar condition the mechanical
elastic sector non-linearity restriction biggest signal output the
IEPE sensor measuring range, its value mostly must determine through
the experiment. In ordinary circumstances when sensor
sensitivity high, its sensitive core body nature 量块 also bigger,
the sensor measuring range relative is smaller. Simultaneously
because the nature 量块 bigger its resonance frequency on somewhat
low is like this easier to stimulate the sensor sensitive core body
the resonant signal, finally causes the harmony vibrational wave
superimposition in to measure on the signal creates the signal
distortion output. Therefore in biggest survey scope choice
time, also must consider was measured the signalling frequency
composition as well as sensor itself 自振 the resonance frequency,
avoids the sensor the resonant component production. Meanwhile
should have the enough security space in the measuring range to
guarantee the signal does not have the distortion.
The acceleration instrument sensitivity demarcates the method
usually to use the comparison test examination, (usually is the output
and the standard sensor which 159 Hz or 80 Hz) vibrates reads
immediately the acceleration value by the school sensor in the spot
frequency for the sensor sensitivity. But to attacks the sensor
the sensitivity through the survey by the school sensor to a series of
different impacts acceleration value output response, obtains the
sensor to input the impact acceleration value in its survey scope and
电输?the between corresponding relations, again obtains through
the value computation with each between difference value smallest
straight line, but this straight line slope is the sensor impact
sensitivity.
Attacks the sensor the non-linear error to be allowed to have
two methods to indicate that, Entire measuring range deviation
or according to partition measuring range miss distance. Former
is refers to the sensor the entire measuring range output for the
datum error percentage, namely regardless of surveys is worth size its
error for presses the erroneous value which the entire measuring range
percentage computation but results in. Are same according to the
partition measuring range miss distance its computational method and
the entire measuring range deviation, but the datum does not use the
entire measuring range but is by partitions the measuring range to
miscount the value. For example the measuring range is the
20000g sensor, like the entire measuring range deviation is 1%, its
miss distance in the entire measuring range is 200g; But when
the sensor according to partition measuring range 5000g, 10000g,
20000g weighs its miss distance, when its error was still 1%, then
sensor at different 3 measuring ranges section inside connection error
then respectively is 50g, 100g, 200g.
• Sensor survey frequency range
The sensor frequency measurement scope is refers to the
sensor in the stipulation frequency response peak-to-peak value error
(±5%, ±10%, ±3dB) the sensor can survey frequency range.
Frequency range high, the lower limit separately is called high,
low frequency up to the frequency. Up to the frequency and the
erroneous direct correlation, the erroneous scope which permits
greatly then its frequency range also on width. As the principle
of equality, the sensor high-frequency response is decided by the
sensor physical characteristics, but the low-frequency response
decided by the sensor and the successor electric circuit comprehensive
electrical parameter. The high frequency cut-off frequency high
sensor inevitably is the volume small, weight light, otherwise uses in
the low frequency survey high sensitivity sensor on the other hand
then the certain volume big and the weight is heavy.
O sensor high frequency survey scope
The sensor high frequency survey target usually
determined by the high frequency cut-off frequency, but the certain
cut-off frequency and the corresponding peak-to-peak value error
relates; Therefore the sensor selects time cannot only look up
to the frequency, must understand corresponding the peak-to-peak value
error value. The sensor frequency peak-to-peak value error is
small not only is the measuring accuracy enhances, more importantly
manifested in the sensor manufacture process to control installs the
precision deviation ability. Moreover because survey object
vibration signal 频率?wider, or the sensor periodic resonance
frequency insufficiently is high, thus is stimulated the resonant
signal wave possibly can superimpose in the survey frequency band on
the signal, creates the bigger measuring error. Therefore when
chooses the sensor the high frequency survey scope besides high
frequency up to the frequency, but also should consider the resonance
frequency to surveys the signal the influence; Certainly outside
this kind of survey frequency band signal also passable the filter has
given the elimination in the measurement system.
In ordinary circumstances sensor high frequency cut-off
frequency AND output signal form (namely electric charge or low
resistivity voltage) irrelevant; But with the sensor structural
design, makes as well as installs the form and the installment quality
all makes is connected. Below the form is makes a qualitative
classification to the different pattern acceleration instrument
high-frequency response, for user when selection contrast and
reference.
The high-frequency response contour, the weight and
the sensitivity sensitive core body form system design installs the form
Best volume small, the weight is light,
low sensitivity compression monolayer
shell general bolt installment
The good general 剪切?nbsp;single-layer shell belt 绝缘?nbsp;attracts
the iron, the cementation
Difference big, the body weight, the high
sensitivity curved curved beam form double-decked shield shell grasps
Please refer to the acceleration instrument high
frequency survey application applies - > the high frequency survey
O sensor low frequency survey scope
Corresponds with the sensor high frequency target, the
sensor low frequency survey target usually determined by the low
frequency cut-off frequency, the similarly certainly low frequency
cut-off frequency and the corresponding peak-to-peak value error is
related. Is different with the high-frequency response, the
sensor low-frequency response has nothing to do with with sensor any
mechanical parameter, but is only decided by the sensor electricity
characteristic parameter. The natural sensor will take the
measurement system some part, will survey the signal the low-frequency
response also to receive the successor instrument electrical parameter
restriction which will use for parts with the sensor. According
to the output signal different form, below separately will give the
discussion to the electric charge output and the low resistivity
voltage output acceleration instrument.
Although the electric charge output acceleration instrument
lists the low frequency cut-off frequency, but generally all gives
pointed out the survey signal the low-frequency response determined by
the successor electric charge amplifier. In practical
application, when the electric charge sensor core body insulation
impedance far is bigger than the electric charge amplifier input end
the input impedance, is composed the measurement system by the sensor
and the electric charge amplifier its low frequency to be supposed to
decide up to the frequency by the electric charge amplifier
low-frequency response. But if the sensor core body insulation
impedance drops, this time the sensor then is possible to affect the
entire measurement system the low-frequency response. Therefore
guarantee core body insulation impedance to electric charge output
acceleration instrument low frequency survey count for much.
Uses for parts regarding the IEPE sensor 恒流 电压? its
is usual low frequency up to the frequency is 0.1 Hz (-5%).
Therefore in the ordinary circumstances the measurement system
low-frequency response is low frequency decided by the sensor up to
the frequency. The general sensor low frequency cut-off
frequency mostly is 0.5 Hz~1 Hz, specially uses in the low frequency
survey sensor low frequency to be possible to expand up to the
frequency to 0.1 Hz. Quite is difficult as a result of the
sensor low frequency verification, therefore the manufacture merchant
generally only provides above 10 Hz the test data. But the
sensor low-frequency response and the first order high pass the filter
extremely to tally, therefore the user may inspect the sensor through
the actual time-constant the reality low-frequency response.
Please refer to the acceleration instrument low frequency survey
application applies - > the low frequency survey
The question also needs to pay attention which with the
IEPE piezoelectricity acceleration instrument survey really low
frequency acceleration signal includes:
• When sensor and 恒流 电压?
alternating current coupling low frequency up to frequency quite, the
measurement system low-frequency response is by the sensor and 恒流
电压?each one low-frequency response combination becomes, this
time the measurement system low frequency cut-off frequency must be
higher than the sensor or 恒流 电压?respective low frequency
cut-off frequency. The ideal measurement system sensor should
use for parts the belt direct current balance 恒流 电压? the
such systematic low-frequency response completely will be decided by
the sensor low frequency up to the frequency.
• When the sensor uses in the really low
frequency survey, whether did the accurate survey low-frequency signal
certainly incompletely decide and the system low-frequency response
characteristic, the system low frequency electrical noise size also
directly will affect the low-frequency signal the survey.
Moreover the sensor transient state temperature response size
also directly will affect the sensor the low frequency survey.
• Sensor whole seal design and electric
cable
O sensor seal form
The piezoelectricity type sensor principle of work is
the use sensitive core body piezoelectric effect, but the
piezoelectricity material produces is the high impedance electric
charge signal. The sensor sensitive core body insulation
impedance and the sensor low frequency survey cut-off frequency has
the relations which mutually corresponds. In order to guarantee
the sensor the low-frequency response, the sensor shell seal design
should cause the sensitive core body and the outside isolation,
prevented the piezoelectricity ceramics receive any pollution to cause
its insulation impedance to drop. The sensitive core body
insulation impedance drops the direct influence performance which
creates to the sensor performance for the low frequency loud strain
bad, is serious when also will create the sensor sensitivity change.
In order to guarantee the sensor the seal characteristic, mostly
the sensor seal uses the laser welding. Meanwhile is diverse in
now the packing material variety, the performance consummates day by
day in the situation, in view of the different use environment, uses
the appropriate packing material substitution laser welding also to be
able to achieve the sensor seals request. But must point out the
different packing material effect difference is very big. North
the wisdom company used overseas well-known depends on the sign the
packing material and the process passes many years environment to
enforce the experimental confirmation.
Tests the scene in the industry scene, for prevented the
electromagnetic field to the sensor signal influence, to uses in the
industry scene on-line monitor sensor often to request the sensor to
use the dual shield shell seal form. The double-decked shield
structure sensor output attachment generally uses the twin core
industry attachment or the union body electric cable output form.
Because the double-decked shield shell unique feature and the
twin core output electric cable, the sensor high-frequency response
generally will receive a bigger restriction, therefore if the user
will have to select the double-decked shield sensor to carry on the
high frequency vibration signal survey, will be supposed discretely to
consider.
O sensor output attachment form
M5 (M6) attaches is the acceleration instrument most
commonly used output attachment form. The M5 attachment
characteristic is the size is smaller, generally uses for parts a
diameter thinner electric cable (2mm or 3mm), compared with suitable
vibration experiment test. Moreover M5 (M6) the structure
pattern is better to the signal shield, therefore because its output
for is easily disturbed to the electric charge output acceleration
instrument the high impedance signal generally uses M5 (M6) to attach.
The survey vibration acceleration instrument attachment
generally avoids using Q9 (BNC), the reason is Q9 (BNC), the adapter
assembly does not have the thread joint, between the component
mechanical linking rigidity to be lower; Therefore if the
acceleration instrument outputs uses Q9 (BNC), it will be able to
affect the sensor the high-frequency response.
Uses in under the industry environment oscillator measurement
acceleration instrument according to be possible to divide into the
tour examination and the on-line monitor, former generally uses the
single-layer shell shield pattern, therefore the sensor attachment
uses M6 or TNC comparatively much attaches. But the on-line
monitor because frequently uses the double-decked shield the structure
pattern, if corresponds electric cable for twin core shielded cable,
therefore twin core industry attachment like M12, M16 as well as C5015
widely are used. Moreover 连体 the electric cable has a
higher reliability, therefore uses under the industry environment the
sensor regardless of is single-layer and the double-decked shield
structure all widely uses 连体 the electric cable for the output
attachment form.
Needs to point out under is regardless of is that one kind of
output attachment adds water surveys all has its limitation, even if
the sensor itself sealing property meets the requirements, after but
the electric cable joint generally all needs to make the special
handling to be able to use in the subaqueous survey.
O electric cable choice
Speaking of outputs for the high impedance signal
electric charge piezoelectricity sensor, does not move for the
guarantee survey signal because the electric cable creates the noise
the influence, the sensor output signal electric cable generally all
uses the low noise electric cable. But outputs for the low
bucking voltage signal IEPE sensor, the low noise electric cable
certainly not necessarily is essential. High frequency, the
low-frequency signal is multiple spindle to surveys the sensor to the
electric cable different request model example the electric cable, the
multichannel high impedance signal electric cable must be each one
independent low noise shielded cable, but the multichannel low
impedance voltage signal then may use the multi- cores stranded wire
to add the shield the electric cable.
Provides in the general sensor electric cable because considers
the electric cable the weight and the cost, Phi 2 mm diameter low
noise electric cable for acceleration instrument standard disposition.
The industry scene uses the sensor generally by IEPE primarily,
the electric cable itself intensity also becomes the important
consideration factor, therefore Phi 3 mm diameter low noise electric
cable and Phi 4.5 mm diameter ordinary coaxial shielded cable becomes
the longest use the electric cable. But for double twists the
core sur- shield to the double-decked shield shell design IEPE sensor
electric cable disposition the electric cable.
In in the acceleration instrument output signal electric cable
choice, besides the electric cable structure, the target which other
frequently considered is the electric cable application temperature as
well as in the industry scene test the electric cable outer layer
material anti-corrosive ability. The most universal use electric
cable insulation material is PVC, the application temperature scope is
-40oC to +105oC. To applies an environment worse situation,
frequently selects the electric cable insulation material is the
teflon; Its application temperature scope is -45oC arrives
+250oC, also the anti-corrosive ability also surpasses other majority
electric cable insulation materials. But the electric cable
flexibility which does with four fluorine materials is worse, the
price also far is higher than the PVC material.
• The external environment to surveys the
sensor the influence
O sensor cross sensitivity and transverse
vibration to survey influence
As a result of the piezoelectricity material own
characteristic, the sensitive core body structural design and the
manufacture precision send the sensor inevitably to produce the output
signal to the transverse vibration, its size expressed by the
crosswise output and the vertical direction output ratio percentage.
According to the different sensitive core body structure and the
materials behavior combination, the compression structure in
theoretically then has the crosswise output, needs to give the
counterbalance through the assembly adjustment way, but is very
difficult in the actual manufacture process to realize the true
counterbalance, therefore the compression acceleration instrument
cross sensitivity leaves 散度 is very big. Compares 剪切?
the design with the compression in theoretically not to have the
crosswise output, the sensor reality crosswise output generally is an
error which causes by the material processing and the assembly
precision. Therefore looked from these two kind of sensitive
cores body actual contrast result, 剪切?the piezoelectricity
acceleration instrument cross sensitivity generally surpasses the
compression pattern. But the sensitive core body for the curved
curved beam structural style cross sensitivity generally said is
situated between 剪切?and between the compression.
According to sensitive core body structure characteristic, when
it transverse vibration vibrates with the vertical direction is same,
also has the corresponding structure frequency response.
Therefore the transverse vibration also similarly possibly has
the resonance in some frequency spot, down to has the bigger
transverse vibration deviation.
The o temperature the influence which outputs to
the sensor
The temperature change causes the sensor output change
is (sensitive core body) the characteristic creates by the
piezoelectricity material. According to the piezoelectricity
material classification, the quartz crystal is been smallest the
temperature influence, but artificially synthesizes the crystal the
application temperature even to be higher than the quartz; But
in 商业?piezoelectricity acceleration instrument most uses
piezoelectricity material or piezoelectricity ceramics. When
piezoelectricity ceramics sensitive core body output high temperature
increases along with the temperature rise, when low temperature
reduces along with temperature drop; But the sensor outputs with
the temperature certainly does not assume the linear variation,
generally said when low temperature the output change must be bigger
than the high temperature time. Because various sensors
temperature response very is in addition difficult to maintain
consistently, therefore actual uses the sensor output generally very
little to use the temperature coefficient to carry on the revision.
The typical temperature response curve or the temperature
coefficient generally only take to the sensor temperature
characteristic weight. The piezoelectricity ceramics to the
temperature response except the material itself characteristic
outside, the production craft also directly will affect the
piezoelectricity material to the temperature response, but the
homogeneous material will leave to the temperature response 散度
will be so. Similarly is the zirconium titanic acid lead
material, the different merchant because uses the different production
craft, causes the same material the piezoelectricity ceramics but its
respective application temperature scope, the temperature response and
the temperature response leaves 散度 the difference to be really
big. The synthesis to the piezoelectricity material basic
research and the production processing craft, at present the domestic
piezoelectricity ceramics temperature characteristic and the overseas
advanced standard compares also has the certain disparity; In
order to guarantee the user to the sensor special request, north the
wisdom uses the import piezoelectricity ceramics, causes the sensor
the elevated temperature service temperature to be possible to use for
a long time under +250oC, moreover the temperature response and its
leaves 散度 is all good to the domestically produced
piezoelectricity ceramics.
The different sensitive core body structural design can have the
different result to the temperature change response. Because the
different material has the different linear expansion coefficient,
therefore the temperature change inevitably causes between the
piezoelectricity material and the metal insert has the stress
variation which different creates because of the linear expansion
coefficient; This kind the stress which produces by the
temperature causes the compression type and the curved curved beam
sensitive core body produces the output signal, sometimes this kind of
temperature change causes the output can be bigger than the oscillator
measurement signal (specially in low frequency survey). Needs
specially to point out the temperature change has the stable state and
the transient state two kinds, the sensor output sensitivity usually
is refers to the stable state height temperature condition along with
the temperature change to the signal output influence. The
transient state temperature change the influence which outputs to the
sensor mainly displays in the low frequency survey, please refer to
the application > the low frequency survey
O sensor base strain sensitivity
The sensor was measured the object in the sensor
installment place strain influence, possibly causes the change which
the sensor outputs. The sensor base strain sensitivity by the
sensor base rigidity, the sensor with was generally measured the
contacted area as well as the sensitive core body structural design
form decided. Cuts the structural style the sensitive core body
and contacted area between the sensor base very small, thus relatively
cuts the core body to be also smaller the base strain function, also
this kind of strain certainly not directly causes the piezoelectricity
ceramics the output. Therefore cuts the sensitive core body
sensor the base strain sensitivity target usually to have to be better
than the compression -like, in does not need to change the sensor the
base rigidity as well as with was measured in the contacted area
situation (will change these two all to affect sensor frequency
response target), 剪切?the sensor generally all will be able to
satisfy the majority of structures survey the request.
O sound field and magnetic field to sensor
influence
The sound wave and the magnetic field also all possibly
cause the signal output to the sensor function, this kind of output
size and the sensor sensitivity ratio is called as for the
piezoelectric pick-up sound sensitivity and the magnetism sensitivity.
The sound sensitivity is expresses the sensor in the strong
sound field (140dB) under the function, acceleration instrument output
value. The acceleration signal output mainly is the sound wave
through to the sensor outside the shell function, again by the outside
shell transmission the signal output which causes for the internal
sensitive core body. Most directly reduces the sensor sound
sensitivity the method is increases the sensor outer covering
thickness, overwhelming majority sensor this target all can satisfy
the usual survey condition.
The magnetism sensitivity is expresses the sensor under the
strong alternating magnetic field function, acceleration instrument
output value. The sensor interior sensitive core body causes the
magnetic force function the signal output is the sensor produces the
magnetism sensitivity basic reason. Therefore in the sensor
design, the metal spare part as far as possible uses does not have the
magnetism or the weak magnetism material reduces the sensor magnetism
sensitivity most direct measure. Moreover the double-decked
shield shell structural style also can reduce the sensor well the
magnetism sensitivity, simultaneously the double-decked shield shell
form also can effectively prevent the magnetic field to outputs the
electrical signal the disturbance.
North Shanghai wisdom 传感 technology
2005.06.08
If wants to have many to the sensor understood or
the demand, please glance over our website or contacts with us:
(China and America pool capital) north Shanghai the wisdom
传感 technology limited company
Address: Shanghai longevity road 1,118 pleased
reach international building A place 17D
Telephone: 021-52396138 Shenzhen office:
13.590368674 billion
Website:  Http://www.bw-sensor.com |
