The Model NGN-3a is an advanced design integrating polar Nephelometer used for the purpose of accurately measuring the scattering coefficient of dry air. The instrument uses a spiral sampler inlet to separate out particles larger than 2.5 microns to satisfy the PM2.5 standard. In addition, a heated measuring chamber dries the air sample to a preset relative humidity value. A relative humidity sensor is mounted in the sample air chamber. By measuring the scattered light over a 170 degree angle, the scattering extinction coefficient, Bscat, is reduced to units of inverse mega meters. Bmass is computed by applying a conversion factor. Bscat and/or Bmass is made available for output to analog and digital data loggers, PC computers or can be read directly from the integrated LCD display. Time, date, barometric pressure, temperature both inside and outside, RH and other important instrument settings are made available on the serial output for data capture. A unique 4-button keypad allows complete control of the NGN-3a. The keypad allows the initiation of clean air and span calibrations to be made easily. Various conversion constants and operating conditions can also be programmed with the keypad. The NGN-3a is entirely self-contained and, except for an external span gas supply, only a low voltage power source is required for operation.
- Continuous accurate measurement of dry PM2.5 aerosol scattering
- Scattering measurement is used as a surrogate for PM2.5 mass. Scattering mass efficiency is user programmable.
- Monitoring of ambient/chamber differential temperature or chamber relative humidity to ensure drying of aerosols
- Sample flow controlled at 7.0 l/min
- LCD interface displays current scattering and mass value
- Control most aspects of the instrument with the external 4-button keypad including calibration checks and many operational variables
- RS-232 at 9600 baud and two analog outputs for data collection via data logger or computer
- PC windows based control and data logging program is included with free updates.
- Operates off 13.8 VDC at 3 amps. Optional power supply is available.
- Minimal on-site servicing required with only annual maintenance recommended.
- LED lamp for very long life of approximately 50,000 hours and reduced power consumption. Effective wavelength is at 530 nm with a 40 nm band width. Other LEDs operating at different wavelengths (470, 505 and 626nm) are available.