vibrating wire transducer for load measurment

Discussion in 'The Projects Forum' started by nikhilsonar29, Sep 29, 2014.

Sep 26, 2014
68
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here i have attached pdf file for strain monitor typ kl66 module(the product of digi sense)
plz find attachements for this,and sir, in the technical specificartion of this transducer they have written that ,signal 12000-18000 hz (5v ttl)
so...my question is how could i measure and calibrate this o/p frequency with using frequency counter
and the measure problem i found that this o/p frequency range is too much for conditioning.
and is it convenient to convert this o/p in voltage by using frequency to voltage converter ?and then calibrate the voltage for load?
again the problem is i didn't found the simple circuit for conversion of f to v for high frequency means--(to convert 12000-18000hz in to the voltage)
(*we r using this transducer for load measurement in elevator)
so...plz give me exact and total solution and if possible give me the simple circuit solution .
thank you,
Regards,
Nikhil.

2. ericgibbs AAC Fanatic!

Jan 29, 2010
3,325
591
hi 29,
You require at least 10 posts before you are allowed to post images.
Eric

Sep 26, 2014
68
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ok eric
but do u have solution

Last edited by a moderator: Sep 29, 2014
4. ericgibbs AAC Fanatic!

Jan 29, 2010
3,325
591
hi 29,
I will try.
I would consider a PIC, used as a frequency counter, a method which often used.
The PIC program would convert the count into a weight value, by using a PIC it would also possible to output the weight to a LCD display or RS232 etc.

What range of weight/s and accuracy is required.?

E

Sep 26, 2014
68
1
hi..sir
i have attached the file
plz do refer

and eric sir
i m not using any microcontroller
pllz give me the solution without micro controller.

• S18E_07_KL66.pdf
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6. ericgibbs AAC Fanatic!

Jan 29, 2010
3,325
591
hi
You could consider a LM2907 or LM2917 IC, to do a Frequency to Voltage conversion.
The signal 12000-18000 hz, F2V conversion would produce a fixed offset voltage at 12000Hz, which you could null to zero using an OPA and then follow that with another OPA to SPAN the 12000 to 18000Hz voltage to give the required weight range.

How do you plan to display the weight,?
E

• LM2917.pdf
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nikhilsonar29 likes this.

Sep 26, 2014
68
1
thanku sir'
the circuit gives 1mv o/p per 1hz frequency
sir , is that the solution u want to suggest me
and let me explain...here when i get the 5 mv o/p mean my i/p frequency is 5hz....when i get suppose, 1volt o/p means my frequency is 1000hz right.
so when the i/p frequency is 12000 hz means the o/p voltage is 12 volt
and what u said me that ,when u get the o/p of 12 volt for 12000hz then null that 12v to zero volt right na?
means this is my zero setting...,
increase the frequency up to 18000 and get the proportional o/p voltage and this is nothing but my full load
this is what u want to suggest me right?
now the query which i having
1) how can i null the voltage when my i/p frequency is 12000hz.(that time my o/p voltage will be 12volt i.e. my vcc)
2)does 6 volt will be the o/p when 18000hz is i/p to the circuit
3)and how could i again do the span adjusment using another opa........,

and eric sir,
if possible plz,give me the total circuit solution ,
coz i think u understand what is my exact question .
and also tell me that does the circuit which i have attached is the right one or not,
thanx
Regards
nikhil

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8. ericgibbs AAC Fanatic!

Jan 29, 2010
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hi,
The base frequency of the sensor is 16,500Hz,+/-500Hz so will the sensor be used for compression/tension or both.?
ie: do you want it to measure Down from 16500 to 12500Hz and Up from 16500 to 18000Hz.

I will look thru a circuit design.
Eric

Sep 26, 2014
68
1
hi,
i m using that sensor in only compression .

thanx eric sir
becoz of u r ans and explanation i exactly come to knw about my vibrating wire transducer
now i have drawn a simple graphical sketch of the sensor and i hav attached plz find,
and plz tel me that am i on the right track?
actually the output of this sensor is given to the main lift controller and depending on the o/p of load (overload or no load or whateve)
controller will decide speed or its operation
Thanku
regards
nikhil

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10. ericgibbs AAC Fanatic!

Jan 29, 2010
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If I am reading the datasheet correctly, in compression the frequency will go down from 16500Hz to say 12500Hz proportionally to the compression, can you confirms this.?
Use a frequency counter and apply tension and compression to the sensor, let me know what you measure.

I asked how do you plan to display the weight and what weight range do you expect.?

Are you sure that this is the correct type of sensor for use with a weigh scale? its designed for measuring micro-strain in a structure,?
E

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Sep 26, 2014
68
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hi,
our purpose of using this sensor is not for weight scale or any displaying purpose.
we are using this sensor in elevator where we mount the sensor at the bottom of lift and it will monitor the load in the lift.
whether load in the lift is overload or in appropriate .(if required extra interval i.e 25%,50%....)
this is what the function of sensor
so i think it will be in compression mode.

and sir i search u on facebook
i found one profile having baby is a timeline photo
is that u?

any problem sir..

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12. ericgibbs AAC Fanatic!

Jan 29, 2010
3,325
591
hi,
Looking at your circuit in post #9. showing 1mV/Hz response for the LM2917. it would tend towards a Vout of 16V! at 16000Hz.

Sep 26, 2014
68
1
hmmm.the same query i have..
coz the vcc for that circuit is 12volt

sorry sir
we are mounting the sensor mostly on top side near the rope.

u can go to the digi sense site and se the extra specification for the product

Last edited by a moderator: Sep 29, 2014
14. ericgibbs AAC Fanatic!

Jan 29, 2010
3,325
591
hi 29,
I have tried a number of idea's using the LM2917 and I cannot get a workable solution.

I appreciate you cannot use a PIC for this app, but it would be the sensible way to use the sensor.
Could you say why you cannot ise an PIC or MCU.?

E

Sep 26, 2014
68
1
hi,eric sir gudmrning here..
sir actually we are already having our micro controller which is dedicated for lift control,
and it is not having inbuilt application for load alert and we can not offered more mcu or pic which will be costly for us...
that is why we are in search of simple circuit for signal conditioning .
plz if any other idea rather than this plz..do suggest

16. ericgibbs AAC Fanatic!

Jan 29, 2010
3,325
591
Morning 29,
I have been thinking of ways to do this, but nothing simple comes to mind.

Consider we had a circuit which produces an output proportional to load, say a mV signal or counter value, how would you use that in your project.?
ie: how would you interface this signal into the lift controller.

Eric
BTW: the cost of a PIC solution would be in hardware around £1 UK, but if you do not have the PIC programming knowledge or equipment, I see your problem.

Sep 26, 2014
68
1
hi,sir..
what i was thinking ..
first convert the frequency o/p of the sensor in to the proportional voltage signal,now depending upon that voltage signal the load can be monitor (not calcualte)
means for the higher (some specific) means during overload the frequency generated by the sensor is more and voltage will be also high,
that is now i can say that the lift is over load and i have to generate the signal that for eg "plz do not enter more persons ,the lift is full loaded"
and for to get to catch that high volt, i was planning to use quad core comparator ic (lm339) ...you can refer the datasheet which is used to compare the to different voltage level and give o/p in two state i.e.high and low
so o/p of this can be drive the relay and further operation can be done.

and sir
actually i dont have any hand on experience on pic
suppose i purchase the pic ic and external component also.
then what will be the next step further
and again the question is about its software part
and i think the software is too high

m i distuurbing u?

Last edited by a moderator: Oct 13, 2014
18. ericgibbs AAC Fanatic!

Jan 29, 2010
3,325
591
Not at all.
I have been busy looking at options, so far nothing will give the required resolution and stability required.
E

19. ericgibbs AAC Fanatic!

Jan 29, 2010
3,325
591
hi,
Would a digital logic solution be acceptable.?
I see that you have 4 zones or 'Set Points' in the 16500,[1] 17000,[2] 17500,[3] 18000,[4] 18000+
Consider a 4060 divider IC with a 32.768KHz crystal, giving 0.5Sec period output, which gates the sensor frequency into say a 4040 IC, 14 stage counter.
Use AND gates to decode the 4 set point counts on the 4040.

Is this project to be used in real lift application or is it a college assignment.?
If its an actual application, I would prefer not to continue suggesting solutions.

E

Sep 26, 2014
68
1

hi sir gudmrning
yes sir this is sort of college asssignment
sir the solution which u have given is. i m going to implement,
but if possible plz give me the deep elaboration about your idea.
i gone through the datasheet of 4060 and 4040,
i think if you give the block diagram description,then it will be more comfortable for me,
means in which should i use the 4060 ic i.e. in counter mode or divider mode.
and how should i interface my vibrating wire transducer with external digital logic circuitry .
and
"which gates the sensor frequency into say a 4040 IC, 14 stage counter." this sentence of reply #21,i dont understand plz explain.
thanx,
Regards
Nikhil.

Last edited by a moderator: Oct 13, 2014