The objective of this problem is to measure body temperature using input capture

Question

The objective of this problem is to measure body temperature using input capture (pulse-width measurement) (Figure 6.25). A shunt resistor is placed in parallel with a thermistor. The
thermistor-shunt combination R has the following linear relationship for temperatures from 90 to 110°F.
R = 100 k? - (T - 90°F) ?1 k?/°F      where R is the resistance of the thermistor-shunt

In other words, the resistance varies from 100 k? to 80 k? as the temperature varies from 90 to 110°F. The range of your system is 90 to 110°F and the resolution should be better than 0.01°F. You will use a 74HC123. On the rise of the B trigger input, the 123 creates a negative logic pulse on its output. The width of the pulse is about 0.28?R?C. Temperature will be measured 100 times a second.

The pulse-width measurement resolution will be 125 ns for the 9S12. The capacitor value so that this pulse width measurement resolution matches the desired temperature resolution of 0.01°F is C >= 44.64 n Farad.

Given this value of C, what is the pulse width at 90°F? Give the answer in both microseconds and E clock cycles.

Given this value of C, what is the pulse width at 110°F? Give the answer in both microseconds and E clock cycles.

Explanation / Answer

We also saw that if this unmarried cord conductor is moved or turned around inside a stationary magnetic discipline, an “EMF”, (Electro-reason force) is caused inside the conductor due to the motion of the conductor via the magnetic flux.

we learnt that a relationship exists among power and Magnetism giving us, as Michael Faraday discovered the effect of “Electromagnetic Induction” and it's miles this fundamental foremost that electrical machines and turbines use to generate a Sinusoidal Waveform for our mains supply.

rotating coil

in the Electromagnetic Induction, academic we said that after a unmarried twine conductor actions thru a everlasting magnetic area thereby slicing its traces of flux, an EMF is brought on in it.

but, if the conductor movements in parallel with the magnetic subject in the case of factors A and B, no lines of flux are reduce and no EMF is precipitated into the conductor, but if the conductor movements at right angles to the magnetic area as in the case of factors C and D, the most quantity of magnetic flux is reduce producing the most quantity of induced EMF.

additionally, because the conductor cuts the magnetic area at special angles among points A and C, zero and 90o the quantity of brought on EMF will lie somewhere between this 0 and most price. Then the quantity of emf precipitated inside a conductor depends at the attitude among the conductor and the magnetic flux as well as the power of the magnetic field.

An AC generator uses the predominant of Faraday’s electromagnetic induction to transform a mechanical power consisting of rotation, into electric electricity, a Sinusoidal Waveform. A easy generator includes a couple of everlasting magnets generating a hard and fast magnetic area between a north and a south pole. interior this magnetic area is a unmarried square loop of cord that may be rotated around a fixed axis permitting it to cut the magnetic flux at numerous angles as proven below.

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