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