The signal conditioning circuit is the most important part for data acquisition system.
The voltage output from the sensor is very small and it is about milivolt to microvolt
such as for a hall effect sensor it is about .0001volt for thermocouple it is about .000001 volt, resistive sensor show about .000001 to about .0000001 of voltage difference when it is in practice. Temperature sensor shows about .001 to .0001 voltage difference in semiconductor sensors.
One might be think that amplification can do all of these job done. But there are so much difficulty still to be solved. One may know about non-linearity hysteresis saturation solution to op-amp and also solution needed to stray capacitance stray inductance and other problem arises in a conditioning circuit.
Conventional op-amp amplifier with proper feedback can make solution to these problem but we need a proper design to do.
Different circuits needed to do the conditioning includes filter clamper modulation and so on.
There are filters are of LOW PASS, HIGH PASS, BAND PASS, BAND STOP type. A low pass filter let the low frequency signal get through the circuit. So to the high pass filter passes the high frequency signal through the circuit. A band pass filter passes a selected band of signal through it. A band stop filter stop the band of selected frequency range.
Low pass high pass filters can be implemented with capacitor and resistors but band pass and band stop type require a separator circuit between the combination of the two basic kind. A opamp can be that separator circuit.
A system in a radio or a television of filter work for the filter that catch a specific channel. The process is to catch all signals in the antenna then using band pass filter select the desired part of it and amplify that portion.
A sensor create signal that is to be fed to a analysis circuit to process it. This is often done using modulation of the desired signal with a high frequency signal. Thus the total signal can be supplied to a long distance. With out modulation this signal cannot go further. TV signal and radio signal is transmitted in this system. The receiver device with a filter select the desired signal (signal range) and then amplify to display it in picture tube.
A modem also send or receive signal using modulation and demodulation.
A data logger is a collector for data from a required sensor or a system. You can store a stream of data from the target and then can analysis of them and have a result. The datalogger takes analogue signal then converting it to digital and then it can further modified or stored.
