device for measuring the resonance frequency of string tensometric sensors with a two-wire connection and an automatic set-up formed by an exciter, to which is connected a sensor, which is further connected via a block of protections to an input differential amplifier, the output of which is via an amplifying active RC band-pass filter with a fixed passband connected to the input of a tunable narrow-band amplifying SC filter, the output of which is via a low-pass filter and via a first AC coupled amplifier connected to a comparator characterized by the fact that the output of the comparator is connected to the first input of a processor and the output of the first AC coupled amplifier, connected to the input of the comparator, is also connected to the first input of an A/D converter, while to its second input is connected the output of a second AC coupled amplifier, the input of which is connected to the output of the active RC band-pass filter with a fixed passband, and where the output of the A/D converter is connected to the second input of the processor, while to its third input is connected the output of a signal (OVERCURRENT) of a current protection of the exciter, and where the processor is further connected by its first control output to the input of a signal ( OVERCURRENT_RESET) of the exciter, by its second control output to the input of a signal (EXCT_POS) of the exciter, by its third control output to the input of a signal (EXCT_NEG) of the exciter, by its fourth control output to the block of protections, by its fifth control output to the input of a signal (G_SET) of the input differential amplifier with variable gain, by its sixth control output to the input of a clock signal (f_clk) of the amplifying SC filter, by its seventh control output to the input of a signal (COMP_ENABLE) of the comparator, and by its eighth control output to the input of a signal (BOOST) of a power supply block powered from a battery, where its controlled output of an excitation voltage (+Vcc) is connected to the block of the exciter, while the exciter is formed by a buffer, which is connected to the control inputs of all switching transistors (M1, M2, M3, M4) in bridge connection, where the source of the first P-channel transistor is connected to the source of the second P-channel transistor and via a first resistor it is connected to the excitation voltage (+Vcc), and where the drain of the first P-channel transistor is connected to both the drain of the first N-channel transistor, and to a first terminal of the sensor, and further the source of the first N-channel transistor is connected to a ground terminal (GND_PWR) and also to the source of the second N-channel transistor, while its drain is connected to both the drain of the second P-channel transistor, and to a second terminal of the sensor, and where between the terminals and a diac is connected, while in parallel to the first resistor is via a second resistor connected the base junction of a PNP transistor, where the emitter of this PNP transistor is connected to the excitation voltage (+Vcc) and its collector is connected via a third resistor to both the parallel combination of a fourth resistor and a first capacitor, which is together with the emitter of the NPN transistor grounded to a ground terminal (GND_DIG), and to the base of a NPN transistor, the collector of which is connected both via a fifth resistor to a power supply voltage (+5V_DIG), and to the both inputs of a first two-input NAND gate where between its inputs and the ground terminal (GND_DIG) is connected a second capacitor, and where the output of the first two-input NAND gate is connected to a one input of a second two-input NAND gate, while its second input is connected to the first output of the processor with the signal ( OVERCURRENT_RESET), and it is further connected to the buffer and to the resetting input of a SR latch formed by a third two-input NAND gate and a fourth two-input NAND gate, where to the output of the second two-input NAND gate is connected the setting input of this SR latch and its output (OVERCURRENT) is connected to both the input of the buffer, and to the third input of the processor, while its second output with the signal (EXCT_POS) and the third output with the signal (EXCT_NEG) are also connected to the inputs of the buffer.