E8500 Instruction & Operations Manual
version 1.010
Page 22 of 45
This sensor has four electrodes. One measures the concentration of carbon monoxide
gas and the other the concentration of any interfering hydrogen gas (It is hydrogen
compensated).
Furthermore, this sensor assembly is designed to provide the CO sensor with a dual
range capability and also to purge the sensor with air, if the CO gas concentration
exceeds the sensor’s diluted upper limit.
If the CO concentration exceeds the sensor’s low range selectable upper limit, a
“dilution” pump turns on mixing dilution air with the sample. A second “dilution” oxygen
sensor measures the resultant concentration of the combined sample and air streams
and computes the correct CO concentration.
(For still higher CO concentrations please refer to the NDIR CO sensor option).
2. NDIR (INFRARED) SENSORS
The Model 8500 emissions analyzer can be equipped with infrared sensor
measurement capability for the measurement of three gases: carbon monoxide (high
range), carbon dioxide and hydrocarbons.
The NDIR bench is designed for operation primarily with measurements of engine
exhausts, according to the California BAR 97 regulations.
The infrared option has the following specifications:
CARBON MONOXIDE
(CO)
0% - 10%
10% - 15%
3% relative
5% relative
CARBON DIOXIDE
(CO
)
0% - 16%
16% - 20%
3% relative
5% relative
HYDROCARBONS
(HC or CxHy)
0 - 0.40 %
0.40 – 1.00 %
1.00 – 3.00 %
3% of Rdg. + 0.01%
5% of Rdg.
8% of Rdg.
3. 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
sensors and also monitors the temperature of the cells as required by the
EPA’s Method CTM-034.
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