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Data Acquisition system

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anushaas

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Sir,

I need to develop a data acquisition mechanism for an ion measurement system

I have the output signal from an electrometer circuit which is in the range of 0 to +10V. It has to be send to some analog input module,
controlled and data sampled by an external personal computer.The sampling rate has to be some 1000 samples per second. Software running on an external computer has to be developed for all data processing. The software is able to display the ion current and number concentration corresponding to the voltage.

How can I select an analog input module/ micro controller that would suit my purpose?Also which software has to be used for the display on a personal computer?

please help me
 

salmanliaquat

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How can I select an analog input module/ micro controller that would suit my purpose?
Search the internet for general purpose micro-controllers. I am sure there are thousands of controllers out there with built-in ADCs (analog to digital converter).
one such controller is AT89C51.
You can sample your signal using ADC peripheral. (But you will have to apply your signal at controller's input through voltage divider since controller operates at 5V).
You can user uart peripheral to serially send data to PC. You can monitor the data on any serial port monitor software like Hyper-terminal. Or you can write Your own win32 application for this purpose.


Regards,
Salman.
 

poorchava

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What I would do:
-it the output of electrometer is unbuffered then use opamp buffer
-divide the signal from electrometer by 2.5 with voltage divider
-pass the signal through second buffer
-apply analog RC or LC lowpass filter to remove components above 2 kHz to prevent aliasing (in case you want to do calculations in frequency domain)
-optionally add resistor+5v1 zener diode to protect MCU from accidental voltge spikes or other abnormal conditions, this may require another buffer.
-feed that voltage to ADC, wither standalone or integrated within MCU. I'd look for something with 12-bit resulution.

Input signal of 0-10V after passing the analog circuitry gets down to 0-4V. This way u can use precision reference source of 4.096V, which gives exactly 1 mV per LSB at 12-bit resolution. In conclusion when u reverse the input division u get measurement with theoretical resolution of 2.5 mV in 10V range. In case you needed higher resolution you may use standalone converters, but higher than 12-bit resolution ADCs are usually of sigma-delta type, which offers somewhat low sampling frequency.

MCU's can communicate with PC in numerous ways. The simplest is RS-232 (COM port) via UART module of MCU. Other way is the USB bus, although it needs USB<->UART converter such as FT232R or an MCU with USB capability.
 
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