Time of collecting air pollutant samples
Sampling time (air monitoring) refers to the time when air pollutant samples are collected. The sampling time of conventional atmospheric monitoring is usually the same as that of conventional meteorological observation, so as to seek the relationship between atmospheric pollution and meteorological conditions, and provide a basis for forecasting atmospheric pollution and determining pollution emission standards. [1]
- Meaning
- Analog signal digital signal converter
- Difference
- Digital signal in time and amplitude Discrete on
Sampling time
The main difference between analog and digital signals is that, digital signal At time and amplitude It is discrete, and analog signals are continuously changing in time and amplitude. Analog signals can pass through analog signals - digital Signal converter That is, A/D is converted into digital signal. Analog signal -- The sampling part of the digital signal converter can be seen as a switch. The switch is closed once every time T passes through, and the closing time is TA. In this way, the signal passing through the switch has changed from a continuous signal to a discontinuous signal, that is, a discrete signal, but it is not a digital signal. It needs to be quantized and coded to become a digital signal. The time interval T between the two closing of the switch is called the sampling period, and the time TA when the switch is closed once is called sampling Hold time. The reciprocal of the sampling period is sampling frequency The minimum value of the sampling frequency is theoretically twice the maximum frequency of the analog signal, that is, the minimum value of the sampling frequency=2 * the maximum frequency of the analog signal. Conversion Time
A/D converter The time required to complete a conversion from analog signal to digital signal is called conversion time, and the reciprocal of conversion time is Conversion frequency 。 
