Fast Isoprene Sensor Description
Hills-Scientific
is pleased to offer the Fast Isoprene Sensor (FIS) to the research community.
Fast Isoprene Sensors in use, worldwide, provide continuous isoprene monitoring and
are used for the direct, rapid measurement of isoprene, from <1 ppb in atmospheric
monitoring to ppm levels in biological and medical research.
The sensors are used in chamber and cuvette studies as continuous monitors supporting
fundamental photosynthetic and process research. They have recently been successfully
applied to measure ambient atmospheric isoprene and as eddy-covariance flux sensors.
The FIS is based on the principle of
chemiluminescence ,
the chemical production of light. When isoprene reacts with ozone the reaction product
is in an excited electronic state which emits light upon relaxation to its ground
state. Measurement of the chemiluminescence is extremely sensitive since it appears
on a near-zero background and because detectors may be used which can detect and
count individual photons.
The combination of high sensitivity, good selectivity over most compounds, and
the fact that isoprene fluxes dominate other hydrocarbons in many measurement areas,
allows the detector to be specific for isoprene. In the FIS, the instrument
continuously pulls sample air into a reflective/inert reaction chamber, where it
reacts with excess ozone produced via corona discharge in oxygen. The reaction of
isoprene with ozone produces violet (430 nm) light, which is viewed with a photon
detector. The detector is single-photon sensitive and produces a digital output of
actual photon counts in a user-specified time period, typically 0.1 to 20 seconds.
Conversion of the photon pulse to a serial data stream occurs within the photon detector,
eliminating analog noise and greatly boosting sensitivity.
Custom software written in LabVIEW-6i
is provided which controls and acquires data from the photon counting module. The
software displays photon counts and isoprene concentration (ppb) in real-time and
writes the data to an ascii file for plotting/analysis using any spreadsheet software.
The FIS signal is linear over all typical measurement regimes (4 orders-of-magnitude
concentration range) allowing simple data interpretation and easy one or two point
calibration.
The sensor has a typical sensitivity drift of ~5% per week, and an autocalibration feature
self-calibrates the instrument on a user defined
schedule.
Electronic mass-flow controllers control all gas flows and monitor reaction cell pressure. Flows, pressure, and instrument status signals
are available as outputs.
www.hills-scientific.com
