DIGITEL Aerosol Sampler DHA-80

High Volume Sampler (HVS)
for autonomous, continuous measurements.

DIGITEL DHA-80 is a system for sampling dust and aerosol particles for later assessment and analysis. The sampler operation range in standard execution is from 100 – 1000 l/min (6 – 60 m³/h). The system is usually called „High Volume Sampler“.

Air-borne dust particles in the sampled air are separated on to Ø 150 mm filters. The flown filter diameter is 140 mm. Sequent 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.
DHA-80 has a container of 15 filters stretched in filter holders. They are changed automatically to the flow position at the pre-set time.
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 the 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“.
For total suspended particulates (TSP) sampling, there are available two differently designed sampling probes:
- a cylinder probe (EMPA/UBA probe); and
- a probe of „open ring slot“ according to VDI as described in GMBI 1983 regarding non-fractionated dust sampling.
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 Digitel DHA-80 are described in the VDI directive No. VDI 2463, sheet 11.

The below-stated figure no. 1 illustrates the mode of operation.

1   Pre-separator
2   Separator chamber
3   Current filter
3a  Filter stock
3b  Used Filter
3c  Exchange elelektronics
4   Microprocessor control
5   Flow meter
5a  Flow sensors
5b  Flow control
5c  Frequency converter
6   Blower
7   Noise baffle
8   Pressure and temperature
    measurement unit
9   Printer Interface
10  RS-232C Interface
11  PC Card Interface
12  Protection lightning print
13  Wind data Interface

11, 12 and 13 are optional

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 blower (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 the noise baffle (7).