Environmental Sensors Co.'s Nitrogen Dioxide Meter is a hand held instrument that measures nitrogen dioxide concentration in a range of 0-20 ppm and a resolution of 0.1 ppm.
The instrument makes it possible to monitor nitrogen dioxide vapor in air. The insturment has an LCD display giving concentrations in ppm, a low battery indicator, and an audible alarm that can be set at any level from 0-20 ppm.
With the touch of a button, the meter displays STEL (average of every 15 min.), TWA (8 hour average) and Peak.
The ZDL-1400 Nitrogen Dioxide data logging meter stores all of the exposure points for up to 5 logs (a log is created in the instrument's internal memory each time it is used). A log contains: date, time, number of exposure points, the interval between each point, and the actual exposure points. All of the log files can be easily uploaded to PC using components vailable within the Microsoft Windows Operation System or the termianl software included with the instrument.
The sensing element of the instrument is an electrochemical cell. The cell is a four-electrode type, which contains a working and an active auxiliary electrode. The signal from the auxiliary electrode is used for temperature compensation and to improve the selectivity of the entire sensor. The sensor response is linear with the concentration of the target gas in air.
Some representative examples of the common compounds and the corresponding signals they are shown below. Care needs to be exercised when using this instrument in the presence of large concentrations of interfering gases. Contact the manufacturer if difficulties are suspected with other gases, or with other usage problems. In addition variations in the baseline, as a result of variations in concentrations of compounds other than the target gas, during the course of the measurement, can impact the reading.