A temperature sensor is used to measure the temperature between -10oF to 200oF.

Question

A temperature sensor is used to measure the temperature between -10oF to 200oF. The sensor outputs the voltages between 1VDC to 5VDC for the full range of temperature measurements, with an excitation/power supply voltage of 15V DC. (15 points) The sensor data needs to be converted to digital data so that controller can use the measurement information. Which A/D converter (from the below list) you would recommend to detect 0.5oF difference in the measurements? (You need to show all the steps) Assume that the available A/D converters are: 2 bit, 4 bit, 8 bit, 10 bit, 12 bit and 16 bit All the available converters have the input voltage range of -5V to 5V and also assume that the reference voltage is input voltage span width

Explanation / Answer

Given temperature range = -10oF to 200oF and A/D converter should detect 0.5oF difference in temperature.

Thus required resolution = 0.5/(200-(-10)) = 1/420

number of levels required in output (1V to 5V) is atleast = (200-(-10))/0.5 =420

number of levels required in A/D converter (input -5V t0 5V) is atleast = 420*(5-(-5))/(5-1) = 1010

Let n bits are used for A/D converter

thus

2n >= 1010

Thus n>= log2(1010)

thus 10bit A/D converter is sufficient

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