Measure resistance using a dc wheatstone bridge

Assignment Help Electrical Engineering

Reference no: EM131507290

Measurement and Instrumentation Laboratory Manual

Experiment 1 - Measurement errors and DC bridges

Part A - Measurement errors

Aim: To measure some unknown color coded resistors, identify & calculate measurement errors.

Calculations:

Using the multi-meter reading as an exact value, what is the error from the nominal value in readings in method 1 & 2.
Using the nominal E24 value of the resistors, what is the error in methods 1-3.
Calculate and measure the resistance of the total series & parallel of the six color coded resistors

Discussion questions:

What are the causes of the errors in method 1, 2 and 3
What is the error between the calculated & measured values in method 4
What if any errors can be attributed to temperature variations during your tests

Part B- Using DC bridge to measuring resistance

Aim: To measure resistance using a DC Wheatstone bridge.

Calculations:

Calculate the measurement error for each resistor

Discussion questions:

To what factors do you attribute measurement errors?
What would be the effect if the excitation voltage for the bridge was a voltage other then 9 Volt?
What would be the effect if the excitation voltage for the bridge was 12V AC?

Experiment 2 - AC bridges

Part A - AC bridge measuring capacitance

Aim: To measure & confirm the value of capacitance of several capacitors wired in various combinations

Calculations:

Calculate the value of each of the colored resistors using the results obtained.
The capacitors come from the E12 range of capacitors, choose the nominal E12 value of the color coded capacitors.
Calculate the total capacitance Method 6 (i), (ii) & (iii)

Discussion questions:

What are the causes errors in the bridge technique
Derive the equation for balance for this bridge.
In your calculations where should you "round" the values.
What would have been the result DC excitation was used for the bridge

Part B- AC bridge measuring inductance.

Aim: To measure & confirm the capacitance of several inductors wired in various combinations using the Maxwell bridge.

Calculations:

For each inductor calculate the value of R1 which would have given a complete balance.

Discussion questions:

Did the fact that we did not use R1 to obtain a precise balance effect the balance that was achieved?
Suggest and draw a simpler bridge which could be used for measuring inductance (similar to the bridge in Part A
Give two disadvantages of such a bridge compared to the Maxwell bridge.
What was the effect of having an excitation frequency of 1 KHz. And why?
What would have been the limitation of using a multi-meter to measure the balance condition?

Experiment 3 - Basic transducer circuits

Part A - Measuring temperature

Aim: To confirm the operation of a circuit which may be used for measuring temperature?

Calculations:

Obtain an approximate equation relating voltage to temperature

Discussion questions:

Does the thermistor have a positive or negative temperature coefficient
What errors are being encountered?
Develop & draw the circuit of a simple bridge where the voltage will be zero at room temperature (say 25 Centigrade) and will read negative for lower temperatures & positive for higher temperatures.

Part B- Measuring light intensity

Aim: To confirm the operation of a circuit which may be used for measuring light intensity.

Discussion questions:

Is the luminous intensity vs. thickness of attenuation layer linear or non-linear? Why?
Is the luminous intensity vs. distance linear or non-linear. Why?
Over what distance can the LDR function as a reflective sensor. What are the limitations?
Develop & draw a circuit which could be used as a detector to measure the reflectivity of a material at a given distance, such that the material produces a positive voltage when it is highly reflective, a negative voltage if it is poorly reflective and 0 Volts when it is medium reflective.

Attachment:- Assignment File.rar

Reference no: EM131507290

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