Response time characteristics of the fast-2D optical array probe detector board

The ability of these probes to accurately measure particle concentration and size partly depends on the response characteristics of the detection system. If the response characteristics are too slow, then small particles are less likely to be detected and the associated effective sample volume decreases.

In an effort to better understand the sample volumes of optical array probes at the National Center for Atmospheric Research, the temporal response of the Fast-2D optical array probe detector board from optical input on the detector to digitization was characterized. The analysis suggests that the board electronics have a response time constant consistently near 50 ns. However, there is also a slow decay term that conforms to a 1/root t decay rate.