E8500 Instruction & Operations Manual
version 1.017
Page 22 of 49
3. PID (Photo-Ionization) SENSOR
The Model 8500 Plus emissions analyzer can be equipped with a PID (photo-ionization)
sensor to measure Volatile Organic Compounds (VOC). The VOC sensor measuring
range is 0 to 200 ppm. When the VOC sensor option is chosen, the VOC mounts into
the manifold where the H2S sensor is usually mounted. The VOC sensor and the H2S
sensor cannot be concurrently installed into the same E8500 Plus analyzer (must
choose one or the other, not both). The VOC sensor option can only be chosen when
the NDIR sensor option is also chosen.
The VOC sensor uses a 10.6 eV PID Lamp for VOC detection. Therefore, the VOC
sensor will detect most volatile organic compounds that have an ionization potential of
10.6 eV or lower.
The only other gases measured by the E8500 Plus and are typically found in a
combustion flue/exhaust gas that have an ionization potential less than 10.6 eV and can
affect the measurement of the VOC sensor are NO (9.25 eV) and H2S (10.46 eV). NO
has a VOC response factor of 7.2, and H2S has a VOC response factor of 3.2. So for
example, if you measure NO at 72 ppm then you should decrease the VOC
measurement by 10 ppm to see the measurement of VOCs other than NO.
4. NON-GAS SENSORS
A. Ambient temperature sensor
This is an IC sensor located near the cold junction of the thermocouple. The
ambient temperature is displayed on the CALIB screen and is used for
temperature compensation. This sensor is located in the vicinity of the gas
