|
The measurement of ionizing radiation is sometimes expressed as being a ''rate'' of counts per unit time registered by a radiation monitoring instrument, of which counts per minute (cpm) and counts per second (cps) are commonly used. Count rate measurements are normally associated with the detection of particles, such as alpha particles and beta particles. However, for gamma ray and X-ray dose measurements a unit such as the sievert is normally used. Both cpm and cps are the rate of detection events registered by the measuring instrument, not the rate of emission from the source of radiation. For radioactive decay measurements it must not be confused with disintegrations per unit time (dpm), which represents the rate of atomic disintegration events at the source of the radiation. 〔 ==Count rates== The count rates of cps and cpm are generally accepted and convenient practical rate measurements. They are not SI units, but are ''de facto'' radiological units of measure in widespread use. Counts per minute (abbreviated to cpm) is a measure of the detection rate of ionization events per minute. Counts are only manifested in the reading of the measuring instrument, and are not an absolute measure of the strength of the source of radiation. Whilst an instrument will display a rate of cpm, it does not have to detect counts for one minute, as it can infer the total per minute from a smaller sampling period. Counts per second (abbreviated to cps) is used for measurements when higher count rates are being encountered, or if hand held radiation survey instruments are being used which can be subject to rapid changes of count rate when the instrument is moved over a source of radiation in a survey area. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「counts per minute」の詳細全文を読む スポンサード リンク
|