With the rapid development of national economy and industrial production, the increasing of industrial safety and social pollution sources, especially in the chemical industrial area, industrial concentration area and surrounding environment, the increasing complexity of work safety management and ecological pollution, and the increasing of safety requirements and environmental pollution loads, the safety and environment accidents happen occasionally.
The photo ionization detector (“PID” for short) is a detector with a extremely high sensitivity and a wide application range, and can detect the volatile organic compounds (“VOC” for short) and other toxic gases with the concentration from 10ppb to 10000ppm (1%).
Compared with the conventional test methods, this detector has such advantages as portable use, small volume, high precision (ppm level), high resolution, rapid response, continuous test, real time and high safety, etc. On one hand, it provides the workers with the real-time information feedback which can help the detection workers make sure that they are in a safety environment without exposure to hazardous chemicals so as to ensure the safety of workers, and automatically monitors and warns the potential leakage accidents, and has a wide prospect in the aspect of accident area confirmation. On the other hand, with the enhancing of the national control and the environmental awareness of the public, various environmental pollution complainants and disputes are increasing so this detector is widely used in the environmental protection equipment for the purpose of environment monitoring.
Principles of sensor
PID is fitted with a UV light source to ionize the organic molecules into the detectable positive and negative ions (ionization), and then the amount of those ions can be detected by an electronic method in order to determine the concentration of the detected gas.
A most outstanding feature of photo ionization is that after the gas is detected, the ions can restore to the original gas and vapor, i.e. it does not damage the detector. Generally speaking, PID is a portable chromatograph without chromatographic column. The organic compounds and other toxic gases with extremely low concentration can be detected. Therefore, PID which is highly sensitive to VOC detection has the incomparable advantage in the emergency accident and environmental monitoring. With the technological development, it has become a powerful tool for environmental protection and real-time safety detection.
Range, resolution and sensitivity
1. After the gas type to be detected is confirmed, the gas concentration shall be determined, and the gas concentration detection range of PID is involved, which normally varies from several ppms to tens of thousands of ppms.
2. The resolution is the minimum variation of the amount that can be detected by the detector in the stipulated measuring range.
3. PID has an extremely high sensitivity which may be up to ppd, and has the outstanding response speed and sensitivity.
Response time
In contact with the reactant gas, PID can output the electric signals through the photovoltaic conversion. T90 means the time needed by the reading of the detector to rise from 0 to 90% of the concentration of the gas detected in the environment.
Temperature and humidity
The output value of the detector may drift due to the influence of temperature and humidity, and thus affect the product service so the evaluation of the impact of temperature and humidity on the detector cannot be neglected.
Detector linearity
PID has the good linearity, and changes linearly in its most range.
4R-PID developed by Intersense independently is a high-performance photo ionization detector, and is featured with rapid response, high moisture resistance and good linearity. With a customizable full range, it can replace the imported product without difference. It can detect thousands of volatile organic compounds (“VOCs” for short) and some inorganic vapors, and be used in various handheld and field-fixed instrument and apparatus and also in various analysis instrument, and widely used in the industrial safety and environmental monitoring field!