Measures airborne particulate concentrations and size in realtime
The DataRAM 4 dual-wavelength nephelometer provides direct and continuously updated readouts of concentrations of airborne dust, smoke, mist and fumes as well as the median particle size. In addition, both air temperature and humidity are displayed. All data can be logged in the integral, large-capacity, nonvolatile memory. Up to 50 000 data blocks can be stored in up to 99 tagged groups.
An on-board audible alarm as well as switched and active alarm outputs are triggered whenever concentrations exceed a user-selected level.
With appropriate aerodynamic particle discriminators, the DataRAM 4 provides measurements correlated with PM10, PM2,5, PM1,0, and respirable fractions.
Determines particle median size regardless of concentration
DataRAM 4's patented two-wavelength particle detection system provides the volume median particle diameter of the sampled aerosol, over the considerably wide concentration range of 1 microgram per cubic metre to 400 milligrams per cubic metre.
Unlike typical particle counting devices, the DataRAM 4 is immune to particle coincidence errors, even at the highest concentrations. Volume median particle sizes down to 0,05 mm can be measured by this spectral nephelometric technique.
Monitors mass concentrations of fine particulates (PM2,5)
The device monitors, in realtime, the concentrations of fine particulates in ambient air by a combination of aerodynamic size preselection, two-wavelength nephelometry, and concurrent sensing/correction for relative humidity. This patented technique provides a continuous measurement of PM2,5, independent of particle size and moisture, without altering the sample stream (ie, without heating, diffusion drying, denuding, etc).
Measures, scattering and Ångström coefficients and visual range
In addition to measuring the mass concentration of airborne particulates, the nephelometer measures the scattering coefficient at two wavelengths (in units of inverse megametres) and computes the coefficient at the reference wavelength of 550 nm, as well as the Ångström exponent (a measure of atmospheric fine particle size). Based on the 550 nm scattering coefficient, the instrument then calculates the visual range (in kilometres).
Complete digital communications
The DataRAM 4 has both RS232 and RS485 data ports for two-way digital communications with personal computers.
Special software (Windows-compatible) provided with the instrument allows data transfer either in realtime or from the DataRAM 4's logging memory for tabular and/or graphic computer presentation. All operational and programming functions of the DataRAM 4 can be controlled from a remote location through the RS485 communications port. Sampling start and stop as well as data transfer can be controlled via modem or other digital transmission paths.
Analog signal and alarm outputs
For added versatility, the DataRAM 4 provides two separate analog signal outputs, updated every second: a voltage output (0-5 V) and a current output (4-20 mA), both programmable over the instrument's full measurement range. Two alarm outputs (and an audible horn) are also included: voltage step (0 to 30 V d.c.) and switching output (2,5 A maximum). The alarm level is also user programmable over the entire measurement range of the instrument.
Detailed diagnostic information
The DataRAM 4 furnishes complete diagnostic data on the functional condition of all its critical elements. Examples include: condition of each of the two sensing sources, optical background level, scattering detector condition, sampling air flow control, internal battery charge status, charging current, etc. Any deviation from normal conditions is flagged on screen.
Self-purging, automatic zeroing, and clean air protection of optics
The field-proven flow configuration includes a large-capacity HEPA filter cartridge directly downstream of the photometric sensing stage. Typically replaced every two years, this filter provides particle-free air that is partially recirculated over all critical optical surfaces to ensure their cleanliness.
For either manual or automatic zeroing, an electronically controlled solenoid valve diverts the entire filtered airstream through the optical sensing chamber to achieve 'zero' air without the need for an external filter.
Self-calibrating internal filter
A 37 mm membrane filter (for which a special holder/adapter is provided) can be used in place of the zeroing HEPA filter cartridge for gravimetric calibration and/or chemical analysis of collected particulates. The DataRAM 4 can be easily calibrated by readjusting the calibration constant to agree with gravimetric measurements obtained from the on-board filter. Because the photometric response of the instrument is exactly linear over its entire operating range, only single point gravimetric calibration is needed. The second point of the straight response line is the zero concentration obtained by self-purging.
Large character screen, menu-driven displays, and scrolling of logged data
A large (48 cm2 active area) LCD screen with four lines of alphanumeric text provides highly visible readouts. The screen has automatic backlighting whenever the DataRAM 4 is powered from the AC line current (through its power supply/charger). The instrument provides users with a variety of self-explanatory informational screens. The main measurement screen, for example, displays realtime and date, mass concentration, time-averaged concentration from the start of the run, and elapsed run time. Logged data can be displayed/scrolled during or after a measurement run, and transferred to a PC.
Several power options
The DataRAM 4's large-capacity rechargeable battery (long-lived, 'memory'-free) provides noninterruptible power to the unit. A charger/power supply is provided for continuous long-term operation. For portable monitoring, the instrument is designed to run without external power for 20 hours. An optional solar power system is available for remote installations.
Expandable to a complete particulates characterisation system
Available accessories extend the capabilities of the DataRAM 4 for a wide range of monitoring/particle sizing applications. Aerodynamic particle size separators (cyclones and jet-to-plate impactors) measure specific size groups such as the thoracic, respirable, PM10, PM2,5 and PM1,0 fractions. An omni-directional sampling inlet and an in-line heater (for mist/fog elimination) are available for ambient air monitoring. An isokinetic sampling probe/nozzle kit enables duct/stack monitoring.
Additional accessories will be available for the DataRAM 4 in the near future, providing a complete systems capability with unparalleled performance flexibility. These accessories/capabilities will include: a patented turntable aerodynamic particle size separator for aerodynamic particle size distribution analysis, and a condensation/nucleation module for ultrafine particle monitoring.
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