Ammonia Monitors

single laser monitor


Aerodyne’s trace gas monitor for ammonia has exceptionally fast response time, high sensitivity and  chemical specificity.  The measurement sensitivity is 0.04 ppb in one second and 0.01 ppb in one minute.  This high sensitivity and fast time response make Aerodyne’s ammonia monitor significantly more capable and versatile than other commercial ammonia monitors.  

The figure at the right demonstrates this sensitivity.  The upper trace is the ammonia mixing ratio in room air plotted versus time for a two hour period.  The Allan plot in the lower half of the figure shows the precision as a function of averaging time.  

The response time of the instrument is shown in the next figure.  In these tests wealternated sampling room air and ammonia from a person’s hand. The time response has a fast component and a slow component.  The fast component is the dominant  part of the time response (80 to 90% of the amplitude) and is characterized by a (1/e) decay time of approximately 0.3 seconds (using a 100 lpm vacuum pump).   This component can be reduced to less than 0.1 seconds using a larger pump.   There is also a smaller amplitude slow component to the response which varies with humidity and is of order 10 seconds.  




Laser Frequency

~967 cm-1

Precision (1 s)

0.04 ppb(1 s)

0.01 ppb (60 s)


5%  or 0.1 ppb

Primary time response

0.1 seconds with 300 liter/min pump