Detcon PI-700 - Manual (Page 10)

Model PI-700
PI-700 Instruction Manual Rev. 2.5 Page 6 of 54
Do not mount in locations where temperatures will exceed the operating temperature limits of the sensor.
Where direct sunlight leads to exceeding the high temperature-operating limit, use a sunshade to help reduce
temperature.
2.3 Sensor Contaminants and Interference
PID VOC and toxic gas sensors will respond to any gas with an ionization potential <10.6eV. This is not a
selective measurement technique, and hence can be used to measure a wide range of gases.
Some of the most commonly present gasses that potentially cause PID interference are listed in Table 5 Gas
Factor Table (refer to Section 9).
The presence of cross-interference gases in an area does not preclude the
use of this sensor technology, although it is likely that the sensor will experience false high readings should
exposure occur.
Some heavy organic molecules may be polymerized onto, or strongly adhere to, the optical filter of the lamp.
When this occurs, the lamp will require cleaning or replacement.
Relative Response Gas Matrix
Table 5 Gas Factor Table shows the response of the PID sensor to a long list of components. It includes the
compound name, synonyms/abbreviations, and chemical formula. It also lists the 10.6eV Response Factor (the
measure of how strong the signal from the sensor is in reference to Isobutylene gas). Isobutylene gas is the
standard reference used with PID sensors, the lower the Response Factor, the stronger the signal.
2.4 Mounting Installation
The PI-700 sensor assembly is designed to be threaded into a ¾” Female NPT fitting of a standard cast metal,
Explosion-Proof Enclosure or Junction Box. Two wrench flats on the upper section of the sensor should be
used to thread the sensor into a ¾” female NPT receiving connection. Thread the sensor up until tight (5 turns
is typically expected) and until the display is pointed in the direction that sensor will normally be viewed and
accessed.
The PI-700 should be vertically oriented so that the sensor points straight down. The explosion-proof
enclosure or junction box would then typically be mounted on a wall or pole. Detcon provides a standard
selection of junction boxes available as sensor accessories (See Figure 7 below). Any appropriately rated
enclosure with a downward facing ¾” NPT female connection will suffice.
When mounting on a wall, it is recommended to use a 0.25”-0.5” spacer underneath the mounting ears of the
Detcon standard J-Box to offset the sensor assembly from the wall and create open access around the sensor
assembly. Spacing requirements for other junction boxes may vary.
When mounting on a pole, secure the Junction Box to a suitable mounting plate and attach the mounting plate
to the pole using U-Bolts. (Pole-Mounting brackets for Detcon J-box accessories are available separately.)