Detcon PI-500 - Manual (Page 3)

3.0 D
ESCRIPTION
Detcon MicroSafe™ Model PI-500 and PI-501 universal VOC sensors are non-intrusive “Smart” sensors designed to
detect and monitor for VOC & toxic gas in the ppm range. One of the primary features of the sensor is its method of
automatic calibration which guides the user through each step via instructions displayed on the backlit LCD. The sen-
sor features LED indicators for FAULT and CAL status and is equipped with a standard analog 4-20 mA output. The
microprocessor supervised electronics are packaged as a universal plug-in transmitter module that mates to a standard
connector board. Both are housed in an explosion proof condulet that includes a glass lens. A 16 character
alpha/numeric indicator is used to display sensor readings as well as the sensor’s menu driven features via a hand-held
programming magnet.
Typical ranges of detection are 0-10ppm, 0-20ppm, 0-50ppm, (using the PI-500) and 0-100ppm, 0-500ppm, and 0-
1,000ppm (using the PI-501). Other ranges are available and all ranges are covered by this manual. To determine sensor
model number, reference the label located on the enclosure cover. To determine primary range, reference labeling on
the sensor head.
3.0.1 Sensor Technology
The sensors are based on a plug-in replaceable miniature PID (Photo-Ionization Detector) sensor technology. The sen-
sor is sensitive to all ambient gases that have ionization potentials of < 10.6 eV, making it highly sensitive but extremely
non-specif ic. The sensor responds to most all toxic VOC compounds and many other toxic gases as well. The sensor is
comprised of a UV emitting lamp that is covered by a specif ic optical f ilter which projects only radiation in the 10.6 eV
range. Target gases that diffuse into the sensor chamber with ionization potentials of < 10.6 eV, are ionized by the radi-
ation and give up free electrons. The free electrons are captured by the high voltage collection grid and provide a cur-
rent signal that is directly proportional to the concentration of the target gas.
PI-500 Toxic Gas Sensors PG.3
e-
Construction of
PID Sensor
Collection Plates
UV Filter Window @ 10.6eV
Electrodeless Lamp Illumination Contacts
Membrane Filter
Krypton
Gas
V
V
Target VOC Compounds
A e-
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