Data acquisition section

 As we use to measuring the temperature by a personal computer. The processor of digital computer can not read or fetch analog data. So, we have to convert the analog signal into digital data or signal. Digital data processing is easier than analog one. Also the digital data storage, conversion much simple. To fetch with digital world like microprocessor we use analog to digital converter (ADC). We use eight bit ADC which convert the analog signal into eight digital bits. This digital data can process easily for next section.
 

To fetch the generated signal to computer, we

1. Have converted the analog signal to digital 8 bits binary data. 

2. Have multiplexed 8 bits binary data to 1. 

3. Have used parallel port to interface. The ADC 0804 does the analog to digital conversion.

The generated analog input signal is applied to its pin 6 and converted 8 bits binary output is available at pins 11-18. The conversion is accomplished only when the WR (pin 2) is active. Although parallel data transmission is faster than serial data transmission, we use serial data conversion because we cannot process eight bit at a time. The parallel port status pin can read external signal .There only five status line. So we have to multiplex the signal for one line. We have connected the pin with parallel port pin-5 to control the conversion with computer. The output of ADC then connected to multiplexer input pins 1-4 and 12-15. The selection pins 9-11 are connected to the parallel port pins 2-4 to collect the required bit out of 8 bits of multiplexer. The output of multiplexer is available at pin 5 is collected to computer with parallel port through pin 15.

Reading the external data can not possible without software . We use matlab for acquiring data. By matlab we can read and write data to personal computer. But we can not measure temperature or complete our work.