8) You need to make a measurement with a pressure sensor and are implementing a

Question

8) You need to make a measurement with a pressure sensor and are implementing a system with the following characteristics o The output of the sensor that you plan to use has a range of OmV to 15mV. o The analog input card you chose to monitor the sensor output has an input range of OV to 10V o The accuracy of the analog input card is 10mV o 50% safety margin is needed in the measurement system. o An amplifier is being used between the sensor and the analog input card a. In order to maximize the resolution of your sensor measurement, but without going over the analog input full scale range, what integer value of gain should your amplifier have? b. What is the accuracy of the analog input card in percentage?

Explanation / Answer

a) Range of sensor output voltage : 0 to 15 mV

   Analog input card output voltage : 0 to 10 V

To maximise the resolution of sensor we should have maximum gain as much possible

Let G be the maximum gain

G = Maximum analog card output / Maximum sensor input

   = 10 V / 15 mV

G = 666.667

Since we want gain in integer

G = 666                                .....................1

This is the required gain of the amplifier

b) Let Acc be accuracy of analog input card in %

Acc = (accuracy of card in Volts / Maximum analog card output voltage)*100

= (10 mV / 10 V)*100

   = 1000 mV / 10 V

   = 1 V / 10 V

Acc = 0.1%                    ....................2

This is the required accuracy of the analog input card in percentage

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