This section consists of non-inverting amplifier and a analog to digital converter. In the previous section we get the voltage which is very small that cannot fetch for further processing. For this reason we have to amplify the previous state output voltage .The work is done by a non-inverting amplifier. Which amplify the input voltage to six times greater than input voltage with same polarity which is fetch to a analog to digital converter. Previous stage output is applied in non-inverting terminal of the op amp. The amplified output amplitude is suitable for forward stage processing.
Saturday, 3 July 2010
Thursday, 1 July 2010
Conditioning or amplification section
This section consists of non-inverting amplifier and a analog to digital converter. In the previous section we get the voltage which is very small that cannot fetch for further processing. For this reason we have to amplify the previous state output voltage .The work is done by a non-inverting amplifier. Which amplify the input voltage to six times greater than input voltage with same polarity which is fetch to a analog to digital converter. Previous stage output is applied in non-inverting terminal of the op amp. The amplified output amplitude is suitable for forward stage processing.
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.
Matlab programmers for reading data from parallel port:
General Format :
Hwlines =addline(parport,0:3,x,‟in‟); x denote data,control or status port value assigned zero ,
oneor two. In denotes the direction of port.
parport=digitalio('parallel','LPT1');
hwlines=addline(parport,0:4,1,'in');
k=getvalue(hwlines)
Matlab programme for write data:
dio = digitalio('parallel','LPT1');
addline(dio,4:7,'out');
val1 = getvalue(dio.Line(1:4))
val3=binvec2dec(val1)
Display section
After completing measurement display need for what value founded. For display we use personal computer. It will display temperature at Celsius scale.Works with parallel must done with care. If two line of port is short circuited that can burn out motherboard of the computer. For this first we find out each line of by short circuit test. Applying input to port vary carefully, to avoid electrical hazard. We do the work for design purpose, for this measurement is not so accurate. Working with of op amp biasing voltage applied carefully and all the measurement done across the point and system common .
Conclusiom
Temperature measurement is an integral part of many process industries. Thus it is essential to have a competent system for this measurement purpose. We deals with the design and implementation of a Personal Computer (PC) based, temperature measurement system. The main sensor used in this case is a commercially available thermistor and custom-made signal conditioning hardware and a data acquisition system. The distinct advantage of this system is its cost effectiveness when compared with conventional temperature measurement systems frequently employed various processes. The thermistor output is a single ended voltage, which is dependent on the transfer function of the thermistor itself. According to this transfer function, the thermistor provides a certain voltage for a certain temperature. The output of the thermistor is then amplified using a non-inverting instrumentation amplifier. Then the instrumentation amplifier output signal is fed to an Analog-to-digital converter (ADC) that will provide digital output. Then output of ADC is connected to a multiplexer which convert digital data from parallel to serial. Finally, this digital information is sent to a Personal Computer (PC) directly via the standard parallel port. Thermistors differ from resistance temperature detectors (RTD) in that the material used in a thermistor is generally a ceramic or polymer, while RTDs use pure metals. The temperature response is also different; RTDs are useful over larger temperature ranges, while thermistors typically achieve a higher precision within a limited temperature range. From thermistor characteristics ,it is non-linear but we use it because of its sensitivity of temperature. Among of temperature sensor it is most sensitive. Non-linearity can be minimized by hardware or software compensation.
we have tried to build up concepts over the major components of our project. But, we want to recommend that the theoretical knowledge is not all in all. The components may not work properly, the connections may be lost anywhere and hazards may come eventually. So, troubleshooting is always required without losing temper. Works with parallel must done with care. If two line of port is short circuited that can burn out motherboard of the computer. For this first we find out each line of by short circuit test. Applying input to port vary carefully, to avoid electrical hazard. We do the work for design purpose, for this measurement is not so accurate. Working with of op amp biasing voltage applied carefully and all the measurement done across the point and system common.
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