DIGITEL Blower DS-02

Controlled High Volume blower
for autonomous and continuous measurements

The DIGITEL blower DS-02 is a part of a system to sample dust and aerosol particles for later assessment and analysis. The sampler operation range in standard execution is 100 to 1000 litres per minute (6 to 60 cubic metres per hour). The system’s usual designation is „High Volume Sampler“.

Air-borne-dust parts in the sampled air are separated onto 150 mm diameter filters. The flown filter diameter is 140 mm. Subsequent gravimetric and analytical analysis could be conducted depending upon the pollutants of interest. Filter material and structure selection (deep filters, porous filters, glass fibres, silica fibres, pulp, Teflon, porosity....) will depend on the analysis purpose. The filter conditioning is important in order to achieve reproducible results.A flow meter controls the selected air flow rate. This value should be calibrated first at the beginning of a measurement session, using a gasmeter or a secondary standard, e.g. an additional flow meter. During air sampling, the pump flow rate is dynamically controlled, so that this value is kept at good reproducibility and at long-term stability despite the deposited filter flow resistance and the sampled ambient air pressure / temperature variation.

An integrated microprocessor unit controls filter changes at the exact preset time and collects all relevant data and events. Hereby the air quantity flowing through the filter is defined with high accuracy.

All mechanical components of the changing automatics as well as the units needed for measurement as sampling probe, pipeline, flow chamber and filter holder, have been improved: they are coated with highly corrosion-resistant and extremely smooth „Ematal“.

Sampling probes PM10/PM2.5 are designed as single-stage impactors. They are intended for operational volume flow of 30 cubic metres per hour.

Sampling probes PM1 are designed as double-stage impactors. They are designed for operational volume flow of 23.1 or 30 cubic metres per hour.

Various remote-control interfaces are built in for operation in automated measurement networks.
The operating principle of the DH-77 is schematically illustrated below.

The air is sampled via a sampling probe (1), using a sampling tube, vertically from the top to the bottom through the filter (3) placed in the flowing chamber (2). With DHA-80, changing of filters is done automatically. After the filter, the transported air quantity is measured using a flow meter with a floater (5). Its double photo-sensor (5a) optically senses the floater position. In connection with the control electronics (5b, 5c), the capacity of the pump (6) is adapted to the rpm control, so that the air quantity keeps the set-point value.
Air pressure and temperature are measured upstream the flow meter and continuously averaged by the controller. A real-time protocol states sampling volumes yielding from the sampling time and controlled volume flow as the core information. The air is released from the instrument with reduced noise through noise baffle (7).