The invention relates to an intelligent sensor to be used for non-invasive measurement of low-intensity biosignals on the body surface. According to the invention, the sensor uses a differential input preamplifier made with a high-pass filter () and an instrumental amplifier (), the preamplifier output signal being passed through a low-pass filter () and a high-pass filter () and then applied to another input of a differential instrumental amplifier (), while, at the other input, there is applied the signal provided by a reference voltage generator () which is controlled by a micro controller of a central processing unit () the output of the instrumental amplifier () is applied through a high-pass filter () to the input of a programmable gain amplifier () whose output is applied to the input of an analogue-to-digital Sigma-Delta converter () and the data obtained at the output of this converter () are sent to the central processing unit () through a serial data channel () with two lines, the data line and the clock signal, through which the gain of the programmable gain amplifier () is also programmed.
