System Setup

Package contents

Unpacking and packing

The instrument is delivered in a sturdy box which is padded with a foam rubber layer.

The NAIS should always be transported in the original box. It can protect the instrument well when left in the hands of a delivery company.

The instrument is weights about 60 kg, so it should be lifted out of the box by at least two persons. The instrument can be can be lifted from the handles. Place it on a firm surface the upright position.

The inlet and exhaust tubes of the instrument are covered during transport. Keep the covers on whenever the instrument is transported but also when the instrumenst is idle for longer periods of time.

Packing the instrument: When lowering the instrument back in the box make sure that the surrounding foam rubber stays flat and does not fold.

Instrument placement

The instrument should be placed on a firm, non-vibrating, level surface. The instrument can tolerate some amount of vibration when measuring (e.g. on board an aircraft or automobile), however any vibration will increase the noise levels.

Inlet considerations

Diffusion losses are highly critical for particles with diameters below 2 nm. Therefore the inlet must be short and must not have any turbulences.

The mobility analyzer is sensitive to insects and fibers that may deposit on the electrodes and cause small corona discharge, electric noise and parasitic currents.

Make sure that rain does not get into the instrument. Choose the angle of the inlet accordingly. Add a bent tube pointing downwards at the end of a horizontal inlet.

Electrical connections

The instrument has a standard power C14 plug and accepts 110V to 240 V AC 50Hz line voltage. The average power requirement of the device is well below 100 W. The power may shortly increase to 150 W for maximum duration of a few seconds when the instrument is starting up.

Series 4 instruments and newer

Series 4 instruments use ethernet for data communications. The following options are available:

In all cases the measurement software should detect the instrument automatically. Typically it is not necessary to manually enter the IP address of the instrument into the measurement software.

Notes for older instruments

Previous generations of NAIS and EAS instruments use a RS-232 interface to connect to the measurement computer. The interface is electrically decoupled from power. The communication between the computer and the instrument runs at 115200 baud. A 5 m long cable should have no problems.

In case the connection with the instrument is unstable and the measurement software shows frequent communication errors it is recommended to experiment with different serial cables and USB-RS232 adapters. Adapters based on FTDI chips have proven to work well (for example FTDI US232R).

Both the instrument and computer should be correctly electrically grounded, i.e. the power outlet where they are connected should have a proper ground pin.

Software installation

There are two programs in the measurement software package provided with the NAIS/EAS.

Spectops for running the measurements and viewing live data.
Retrospect for viewing and reprocessing the results later.

In addition, each instrument have individual instrument configuration files which are necessary for running measurements. These contain calibration info and other instrument specific data.

To install the program on a computer, please follow the steps:

  1. Create a folder on your computer where you want the software to reside.

    Usually the measurement results will be stored into a sub-folder of that folder. So make sure that there is sufficient free disk space.

  2. Download the instrument configuration package and the compatible measurement software package from your instrument page at the address:

  3. Extract both files into the same folder.

    (Spectops-package.exe is a self-extracting archive.)

  4. Run the Spectops program that was just extracted.

  5. Open the measurement setup file in Spectops (Menu: File → Open...).

  6. (a) Choose "Auto discover" for finding the instrument on the local network

    (b) Specify the IP address of the instrument if auto discover does not work

    (c) for instruments with a RS-232 connection: select the correct serial port.

  7. Specify the measurement cycle or use the default.
    For example: "particles 60, ions 60, offset 30"

  8. Run the measurements.

  9. Optional: Use "Create shortcut..." from File menu to create a shortcut that will automatically start measurements with the current measurement setup file.

    Place the shortcut into the Windows Startup folder to start the measurement automatically when the computer starts.

Website access: The software and instrument pages are only accessible to registered users. Please send an email to Airel Support at to get an account.

Retrospect use: Retrospect does not use the instrument package. So, for simply browsing the measurement data, only the measurement software package is needed.

First run

The instrument needs a minimum of 5 minutes and at least three measurement cycles to "warm-up". Before that, the software may show diagnostic warnings and the data will not be correct.

The blowers will start and stabilize immediately at startup, so first check that the blowers are working and airflows are not obstructed.

When measuring in particle mode for the first time after the software has been installed, the postfilter voltages will not be ideal. It may take at least 30 minutes and possibly up to a few hours until the posftilter adjustment algorithm has settled on good value (see Postfilter).

If you are unsure whether the instrument is operating correctly, collect at least 1 hour of data and send it to Airel ( Make sure that you send all the data files (records, log and spectra). Please send only block average files initially.

Further checks and diagnostics can be carried out via remote access to the measurement computer (for example, using Teamviewer).

For experienced users: See Diagnostic Checks for a list of conditions that can be checked to make sure that the instrument runs correctly.