Data Acquisition Web

Some sensors give an output signal when just exposed to the measurand, as ph electrodes and solar cells do. But many others as strain gauges, Hall effect sensors, LVDT need DC or AC voltages or currents to measure.

DC Current source, DC voltage source, AC current source, AC voltage source circuits are found elsewhere with different grades of stability, noise and temperature coefficients. Be sure to choose the right one for your sensor, because the best sensor can be spoiled by a bad polarizing circuit. Some times sensors are used in pairs or in groups of four in a bridge configuration, mostly as Wheatstone bridges, but if there are frequency dependence involved, Wien’s bridge could be the choice.

Many times the first stage after the sensor is an instrumentation amplifier. Instrumentation amplifiers are differential amplifiers with high common mode rejection ratio, stable gain and very high input impedance. On the analog arsenal there are, log amplifiers, multiplying amplifiers, and many others linear and non linear signal conditioning circuits. Again, be sure to choose the right one for your sensor.

Today digital readout is maybe the cheapest. Then even in the simplest cases an AD converter is present in the system. Again, be sure to choose the right one for your system. Digital signals can be stored and transmitted, some times forming a network, and logged in a central computer for further processing.