FIELD: measuring devices. SUBSTANCE: device calculates equation 
, where C is known constant, X is variable. This equation is solved using ratios in rectangular triangle, which hypotenuse is equal to 
and leg is equal to 
, angle between hypotenuse and leg is 
, while 
, so 
. Corresponding device has unit for calculation of square root of sum of known constant and variable, master oscillator, quadrature source of reference voltage, comparison unit and memory unit. Device excludes error in method of measuring. EFFECT: increased precision, low instrumental error, increased dynamic range for input signals. 2 cl, 2 dwg
