What is the difference between the principles of the PID and the FID in a portable VOC gas detector?
VOC usually refers to the type of volatile organic compounds that cause harm, with a wide variety of types and sources, and is one of the pollution hazards in modern life and production. A portable VOC gas detector can detect the concentration range of VOC and determine the degree of harm. Among them, portable VOC gas detectors based on PID principle and FID principle are commonly used. What are the differences between the two?
1, The principle of detection is different
The portable VOC gas detector based on PID principle uses ultraviolet light to ionize the sample gas during detection, in order to monitor the concentration of VOC. After the sample gas is discharged, secondary analysis can still be performed on the sample gas. However, the VOC online monitoring instrument based on FID principle uses hydrogen flame to ionize the sample gas during detection. After the combustion of the sample gas is discharged, the composition and concentration of VOC gas change, and secondary analysis cannot be performed.
2, Different installation and use
In terms of installation and use, the VOC gas detector using PID is compact, portable, easy to install, and cost-effective. The VOC gas detector based on the FID principle has higher installation difficulty and technical requirements due to the need for hydrogen cylinders or online hydrogen generators, and its cost is also higher than that of the PID principle.
3, The types of gases detected are different
The VOC detected by PID principle includes saturated and unsaturated hydrocarbons, aromatics, amines, halogenated hydrocarbons, thiohydrocarbons, alcohols, lipids, and hydrazine gases; The FID principle is widely used for the detection of volatile hydrocarbons and many carbon containing compounds.
4, The scope of monitoring varies
The monitoring range of FID principle is 1-50000 ppm, while the monitoring range of PID principle is 1-4000 ppm or 0.1-10000 pm; When the concentration of VOC exceeds 10000ppm, the linearity of FID is better. So when users choose a VOC gas detector, they need to decide based on the on-site VOC concentration.
