Reference no: EM132932109

Measurement Systems

Assignment

Assignment Problem Background

You are a biokineticist and you want to development a system to measure the grasping force of a human hand. You expect that the grasping force will range between 0 and 380 N. To measure the hand grip force, an individual must grasp a hollow cylinder. When the individual closes their hand around the cylinder, it decreases in diameter. As the diameter of the cylinder decreases, a pin pushes onto a load cell, which in turn measures the force. This is shown in Figure 1.

The measured force must be displayed on LCD screen and simultaneously sent to a computer so that the individual participant performing the grasp can visualise the change in their grip force in real-time. An 8-bit micro-controller with a sampling rate of 10 MHz will be used to facilitate this requirement.

From your experience you expect that grip force to change with time and follow a specific pattern. This pattern must be generated using the code in Appendix B.

The system will need to be transported all over the world, to record data from numerous populations of people. The system will be always be used indoors, in a laboratory environment. For each environment, the measurement system must be calibrated. Calibration must be done as follows:
• A special apparatus will be used to apply a known force of 100 N to grasp the cylinder.
• The output measurement is allowed to settle as shown on an LCD screen connected to the micro-controller.
• A button is then pressed to compute the offset voltage and store it in memory
• The LCD display then shows a value of 100 N.

Figure 1: depiction of how human grasp force will be measured using a compressible metal hollow cylinder. a) shows the cylinder viewed from the top, while b) shows the cylinder viewed from the side.

3 Tasks
It is your job to design an appropriate force measurement system to meet the abovementioned specifications. Assume that all resistors have a tolerance of 1%. Complete all the tasks below.

3.1 Task 1 Choose an appropriate sensor from the options in Appendix A. Explain your choice.

3.2 Task 2 Generate, plot and analyse your input force signal.

3.3 Task 3 Design a suitable amplification circuit. Show the circuit diagram and explain your design choices.

3.4 Task 4 Design any signal filtering system needed for your measurement system. Explain the need for the filters. Explain your thinking that informed your design.

3.5 Task 5 Draw a complete circuit diagram (as far as possible) of your force measurement system. Outline and annotate the stages or building blocks of your system.

3.6 Task 6 The new version of the measurement system is to be used for another experiment where in the input force (f) will change with time (t) according to the following equation: f(t) = sin(2Π5t)

A colleague suggests introducing a high-pass filter to the new version in order to get rid of any low-frequency noise and drifts. He suggests a cut-off frequency of 1 Hz. Critically analyse his suggestion to determine whether you will take his advice or not.

3.7 Task 7 Calculate the maximum error within in your force signal at the output of the analogueto-digital converter.

3.8 Task 8 Write basic pseudo-code to explain the logical functions of the micro-controller.

Attachment:- Measurement Systems.rar