Hardware Design for Noise Reduction in Data Acquisition Modules

In the introduction of this paper are briefly presented the most important sources of noise in data acquisition modules and classical techniques for reducing this noise. Are clarified the types of input configurations available on data acquisition devices and are explained how should be choused and used the best configuration for an application. Also are analyzed the interference noise pick up mechanisms and the methods to minimize interference noise by proper cabling and shielding. After that it is described a new method of noise reduction, in which a square-wave signal is modulated with signal from sensor (input signal) and then it is applied at instrumentation amplifier. The amplified signal is modulated again with the same signal type before analog to digital conversion. The noise and offset voltage that appears due amplifier and from external sources are modulated only once by the final multiplier and translated to the harmonics. By using a low-pass filter, results a clear output signal with reduced noise components. Further low pass filtering it is necessary for eliminating the residual offset voltages that appears due to the use of this technique.