| 摘要 |
PURPOSE:To accurately calculate a low level signal, by storing the output of a measuring processing part when the input terminal of said processing part is shortcircuited and calculating the difference between an input signal and the content of memory when the level of the input level at the time of measurement is definite value or less. CONSTITUTION:Prior to starting measurement, the output of a measuring processing part, for example, a vibrometer 10, when the input terminal of the vibrometer 10 was shortcircuited, is processed by a frequency analyzer 11 and the spectrum is stored in memory 13 through a signal level judge circuit 12. Subsequently, the shortcircuiting of the input terminal is released and input to be measured is processed by the vibrometer 10 and the frequency analyzer 11 to judge a signal level in the judge circuit 12. When the judge result is a reference level or more, output Sout is performed as it is but, when said result is the reference level or less, the value stored in memory 13 is subtracted from the measured level in an adder 14 to calculate the measured value of a low level. This control is performed by the indication signals (a)-(b) of an indication control circuit 15. By this method, accurate measurement is performed even for the low level signal. |
