Pegasor PN-PTI sensor is designed to provide an integrated sample treatment and sensing element for accurate,repeatable particle number concentration measurement. Specific consideration is given to particle number testingfor periodic technical inspection (PN-PTI).

The sensor incorporates hydrocarbon removal by a sample heatingelement together with high temperature particle measurement. The particle detection is based on diffusion chargingtechnology, more specifically escaping current technology, allowing very high contamination protection for the activeelements and no need for sample filtration or pump exposure to sample. The sensor uses an advanced form ofdynamic trap sequencing to fulfill the detection efficiency requirements at different particle sizes.

The sensor dimensions (without thermal insulation) are 230 mm x 110 mm x 90 mm. The required insulation materialthickness is 1.5cm to constrain the heater power below 60W.

Schematic operation

The sensor operates as an ejector pumped, advanced diffusion charger. The sample is pulled in the sensor viasampling tube, either nonheated or lightly heated (<60 °C) to remove any condensation. In standby mode the zero airmagnetic valve is open, pushing filtered zero air in the sensor and allowing sensor to be rapidly ready formeasurement, while giving opportunity to do zero check and at the same time protecting the sensor from particleloading.

The first part of the sensor has a heating section at 200°C, evaporating any volatile species from the sample. Thesample is kept at elevated temperature throughout the measurement, as the sensor head is kept at high temperatureof 150 °C throughout the sample path. After the heater, the sample is charged in the ejector, driven by ionized air.After ionization, the electrostatic trap removes excess ions and at the same time performs fast sizing action. Thesizing, done by fast switching of the trap is used to apply calibration for the number concentration from the current