DIGITEL Aerosol Sampler DPA96

Low Volume Sampler (LVS)
for autonomous and continuous measurements

The DIGITEL blower DPA96 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 5 to 50 litres per minute (0,3 to 3 cubic metres per hour). The system’s usual designation is „Low Volume Sampler“.

For different applications different types of sampler are available. The current types are listed at the technical data.

Air-borne-dust parts in the sampled air are separated on to 47 mm diameter filters, DNPH tubes or the like. 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.

The DPA96 has a multifunctional interface for triggering a mechanical 16-way-valve or an 8-port magnet valve. By means of these returnable valves different filter can be flown dependent upon variable external defaults (f.e. wind dependent or time controlled)
Optional filter holders, washbottles, sampling test tubes, etc. can be connected.

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.

Different pre-separators are available for the sampling concerning continuous and discontinuous operation for variable flow rates and separation levels.
Various remote-control interfaces are built in for operation in automated measurement networks.
The operating principle is schematically illustrated below.

1   Suction nipple
2   Pre-filter
3   Vacuum pump closed
4   Filter / Baffle
5   Cooling unit
6   Flow meter
7   Outlet nipple
8   Infrared photo cell
9   Control electronic
10  Frequency converter
11  Rotating current motor
12  Microprocessor control
    with keyboard
    and LCD-Display
13  Pressure /
    Temperature module
14  Manometer
15  Valve triggering
    on SUB D socket
16  Network connection 220V
17  Master switch
18  Network filter /
    Power supply
19  PCMCIA Card 256 kByte
20  RS-232C Data logging/
    Remote control
21  Wind data connection
22  Pressure / Temperature
    and
    Humidity sensor (Option)
23  Sampling head

Specifications of the programmable blower DPA96 :

Flow rate regulation :
Continuous air flow rate by regulation of the suction power via flow meter with photo electric floater sensor.
Flow rate readible on the precision-flow rate meter (calibrated by hand).
Desired value of the total flow rate zone continuously adjustable.
Display of the suction utilization.

Blower:
Controlled rotation frequency, special sealed carbon oil-less rotary air compressor with electronic commuting brushless motor for extreme low electrical power consumption and a long lasting life time.

Pressure and temperature measurement of the air in the flow rate measurement system:
for each filter a correction factor will be issued (worked out of the average temperature and the average pressure of the measuring air) On the basis of this correction factor and the tuned flow rate the standard volume for each filter can be calculated.

Controlling:
Microprocessor-controlling
Flow rate programs by dialog via key pad and LCD-display adjustable
Battery backed data memory
Handling time to program start programmable
RS-232C printer interface.
RS-232C interface for remote inquiry and remote control
At the use of a returnable valve each port is programmable
Manual operating possible.
Overload display and overload processing
Memory cards write -/read device for PCMCIA - cards.
The write/read device is able to read and write the memory cards PCMCIA/JEIDA4 of the compatible 68-Pin - Format. The write/read device is connected internally at the data bus.

Logging:
In the logging are included: all internal status- and failure indications, the calculated correction factors, the collect time, the collecting volumes and the average values of the air temperature and air pressure in the measuring system during the sampling. Furthermore the collected and the prepared data of the optional connected external sensors (e.g..: temperature, humidity, pressure, wind direction, wind velocity etc..) are also logged resp. processed.
The logging can be realised on a printer, a serial (RS-232C) interface and a convertible memory card (PCMCIA/JEIDA4 compatible 68-pin - format).
The saved data on the memory card are shown in an ordinary tabular form and can be processed by any tabular processing program.