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Project for exam please help...

Timotei

May 30, 2017
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Hi i have an exam to take and i need explanation on all these questions on the file attached

1.determine the parameters in tha configuration.

2 for the op amp with galvanic isolation find R1,R2,R3,R4.

3.DETERMINE what transducer this is and explain its functionality.

4.we want to measure the compresiion force in the 0-100N domain with a rezolution of 0.5N/div...make the block diagram, the number of bits and the logic of conversion

5.write and explain the sampling theorem in the area of data aquisition.


Pls help...thanks
 

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davenn

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Sep 5, 2009
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we are not going to directly answer your homework

you need to show us that you are making a good effort
You should have been learning about this stuff in class, so you should know at least the basics of what is being asked
else the teacher wouldn't be testing you on it
 

Audioguru

Sep 24, 2016
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We speak English on this website. Your homework is in a foreign language. Isn't there a forum in your country?
 

Audioguru

Sep 24, 2016
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I wonder if the "tranductorul" shown in the attachment is actually a solenoid?
 

Harald Kapp

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It depends on what you define as solenoid. As I see it, this is a device with a movabel iron core and 3 coils. One coil (tensiune alimentare) is fed a sinusoidal voltage (or current, but for this exam it's a voltage). The two other coils each deliver an output voltage which is proportional to the psosition of the iron core.
The task is to explain how this works.
@Timotei : Here's a hint: consider the magnetic flux in different positions of the iron core and the influence of this flux on the two output coils.

A few more hints for the other questions:
  1. You sgould know the meaning of Cx=20 ms/div and Cy=1 V/div. From that you can 'measure' the requested parameters by reading the values for T, f, U(t) and Umax from the screen Ueff needs to be calculated. You should know the required equation.
  2. We assume th amplifiers OC1 and OC2 have sufficient pos. and neg. suply voltage so we don't have to care about these. We also assume a steady state situation (or at least very low frequencies) so we don't have to care for frequency dependencies and such.
    A positive input voltage to Ao1 will turn on the NPN transistor which in turn will lead to current flowing throug the LEds of OC1 and OC2.This current in turn will turn on the transistor in OC1, thus allowing current I2 to flow. Current I2 is given as 15 mA. It will develop a voltage drop across R3, thus creating a negative volate at the connection between R3, R4 and the collector of OC1. This in effect an inverting opamp configuration. Try to solve the question using this as a starting point. Remember that the differential input voltage of an opamp in normal operation is ~0V (=0 V for the purpose of this task) and that there is only a very small input current into the opamp's inputs (assume Iin=0 mA for the purpose of this task). Also gain is usually assumed as infinite for such a question.
  3. See above
  4. You will need a pressure sensor/transducer, possibly a gain stage or attenuator and an analog-to-digital converter. The number of bits can be calculated from the number of steps between 0 N and 100 N at a resolution of 0.5 N.
  5. The sampling theorem is explained on many web pages. Look up the one explanation that suits you best.
 

duke37

Jan 9, 2011
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The three coil device is often called a LVDT. Linear variable differential transformer. With phase sensitive detection they can be very sensitive.
 
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