The Integrated Dilution System (IDS) allows to use the NAIS instrument with sample air flow rates between 0.5 and 10 l/min. This corresponds to dilution coefficients from ~100 to ~ 5, as the normal sample flow rate of the NAIS is 54 l/min.
The dilution system is software controlled, automatic and integrated into the NAIS data acquisition system.
Principle of operation
The whole IDS-NAIS flow system has one inlet, one outlet, and is otherwise closed. Dilution is performed by mixing the aerosol sample with filtered clean air that is recirculated from the outlet of the NAIS.
The system controls and monitors the flow rate at the outlet of the IDS. The flow rate is equal to the sample flow rate at the inlet.
The user can select the required diluter sample flow using the NAIS measurement software. The system will automatically adjust the air flow rates to accomodate that.
The IDS consists of two parts: the mixer and the dilution flow controller.
- The mixer carries out mixing of the sample air and clean dilution air. The mixer is placed on the end of the NAIS sample inlet. It should be as near to the aerosol source as possible to keep the residence time in the sampling line to the minimum.
- The flow controller performs filtering and flow control. The flow controller keeps a constant flow rate at the system outlet. The flow controller is connected to the NAIS via a RS-232-USB cable and is controlled by the NAIS data acquisition software.
The flow controller also includes a blower which can be switched on in case the diluter sample flow rate does not reach the required value (for example due to a long or narrow inlet line).
If the IDS will be used in underpressure or overpressure conditions then it is recommended to contact Airel Ltd. to discuss specific details how to better ensure the proper operation of the system.