PID (PhotoioniSation Detector) Sensors

How PID Sensors Work

PID sensors work by using ultraviolet light to ionise gas molecules. These sensors contain a UV lamp that emits light to break down the VOCs into ions, producing a current that is proportional to the gas concentration. Commonly used in settings such as industrial safety, environmental monitoring, and hazardous material handling, PID sensors play a crucial role in ensuring worker safety and preventing health hazards in contaminated environments.

• Accuracy

PID sensors offer high accuracy in detecting VOCs, making them a reliable choice for industries where gas leaks or VOC emissions pose serious risks. They measure concentrations in parts per million (ppm) or even lower. However, environmental factors like humidity, dirt, and the presence of interfering gases can impact their precision. Regular calibration and maintenance are necessary to ensure accuracy, with manufacturers typically recommending recalibration based on usage and environmental conditions. Despite potential vulnerabilities, PID sensors remain trusted for their fast response times and ability to detect low-level concentrations of gases.

• Reliability

Photoionization detectors are generally reliable, but their performance can be affected by contamination of the electrode stack and degradation of the UV lamp. Contaminated sensors may continue to operate, but lose sensitivity in detecting VOCs. While the lifespan of a PID sensor’s lamp can last up to 5,000 hours, its performance may degrade in dirty or heavily contaminated environments, which makes regular cleaning and proper handling essential to prolonging its operational life.

• Maintenance

Maintaining PID sensors involves regular cleaning of the UV lamp and electrode stack, as well as recalibration. The frequency of maintenance depends on the environment in which the sensor is used. In clean environments, monthly calibration might suffice, while more frequent checks are required in contaminated settings. Replacing the electrode stack and cleaning the lamp are critical to ensure the sensor continues to function accurately. PID sensors may need replacement sooner in environments with high VOC concentrations or particulate contamination. Regular bump testing and calibration can identify faulty sensors before they pose a safety risk.

Limitations of PID Sensors

• Sensitive to humidity and dirty environments
• The electrode stack has a limited lifespan, especially in contaminated sites
• Requires regular maintenance to ensure proper functionality
• Lamp degradation over time reduces sensitivity
• Interference from certain gases may impact accuracy