1. Using Multisim, construct a simple 0-5V DC digital voltmeter using the ADC (rather than the ADC0804) and the 74185 IC to convert the binary output into BCD, which will be displayed on two 7-segment displays. The 74185 IC will be used to convert a 6-bit binary number to a 2-digit BCD number. Note that the 2 least significant A/D output bits are left unconnected (using only 6 bits of resolution). Calibrate the digital voltmeter by applying 5V to the analog in (measured with a DVM) and adjusting the potentiometer until the 7 segment display reads 5.0 (the decimal point is assumed to be in the middle). Test the accuracy of the digital voltmeter with several different values for analog in.
2. Using Multisim, use the A/D converter to digitize a sine-wave input signal and then reconvert the representative digital signal into an analog signal with the DAC (in Multisim this is called a VDAC). Connect the input of the D/A converter to the output of the A/D converter. Make sure the MSB out is connected to the MSB in. Adjust the input sine wave to 2.5Vp-p with a DC offset of 1.25 volts (i.e., the sine wave goes from 0 to 2.5V). Adjust the Vref/2 voltage using the potentiometer so that the analog input span on the ADC is 0 to 2.5V. Use an oscilloscope to compare the analog input and output waveforms. Set the analog input signal frequency to 200Hz and observe the resultant analog output signal. Increase the input signal frequency and note the effect on the resultant output signal.© BrainMass Inc. brainmass.com October 10, 2019, 1:21 am ad1c9bdddf
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