Patent ID: 7928365

Claim:
A time-of-flight mass spectrometer, comprising: detecting means for detecting an ion which is ionized from a sample and accelerated to fly; an A/D converter which samples an analog signal output from the detecting means and converts the sampled analog signal to a digital signal; a first memory circuit which stores sampling data by adding up said sampling data to a previously stored sampling data; a second memory circuit which stores peak voltage values and their frequencies of said sampling data output from said A/D converter by adding up said peak voltage values and their frequencies to previously stored peak voltage values and their frequencies; a computing unit which performs a predetermined process based on a result of the adding in the second memory circuit to calculate a threshold level; a third memory circuit which extracts data exceeding the threshold level, which is an output signal from said computing unit, from said sampling data added and stored in said first memory circuit, and stores the extracted data; and a CPU which receives the extracted data stored in the third memory circuit and processes the received extracted data, wherein the first memory circuit stores sampling data by adding up (1 st -(n) th) sampling data one after another, wherein the timing of adding up (1 st -(n-1) th) peak voltage and their frequencies of the second memory circuit is same as the timing of adding up (1 st -(n-1) th) sampling data of the first memory circuit, and wherein the computing unit calculates the threshold level based on the result of (1 st -(n-1) th) addition of the second memory circuit and transmits the threshold level at the timing of the (n) th addition of the first memory circuit.