O2 sensor-What I have learnt
01-30-2008, 01:03 PM
#16
Nordschleife Master
http://en.wikipedia.org/wiki/Oxygen_sensor
"The sensor element is a ceramic cylinder plated inside and out with porous platinum electrodes; the whole assembly is protected by a metal gauze. It operates by measuring the difference in oxygen between the exhaust gas and the external air, and generates a voltage or changes its resistance depending on the difference between the two. The sensors only work effectively when heated to approximately 300°C, so most newer lambda probes have heating elements encased in the ceramic to bring the ceramic tip up to temperature quickly when the exhaust is cold. The probe typically has four wires attached to it: two for the lambda output, and two for the heater power, although some automakers use a common ground for the sensor element and heaters, resulting in three wires. Earlier non-electrically-heater sensors had one or two wires"
"It operates by measuring the difference in oxygen between the exhaust gas and the external air,"
"The sensor element is a ceramic cylinder plated inside and out with porous platinum electrodes; the whole assembly is protected by a metal gauze. It operates by measuring the difference in oxygen between the exhaust gas and the external air, and generates a voltage or changes its resistance depending on the difference between the two. The sensors only work effectively when heated to approximately 300°C, so most newer lambda probes have heating elements encased in the ceramic to bring the ceramic tip up to temperature quickly when the exhaust is cold. The probe typically has four wires attached to it: two for the lambda output, and two for the heater power, although some automakers use a common ground for the sensor element and heaters, resulting in three wires. Earlier non-electrically-heater sensors had one or two wires"
"It operates by measuring the difference in oxygen between the exhaust gas and the external air,"
01-30-2008, 01:43 PM
#17
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http://en.wikipedia.org/wiki/Oxygen_sensor
"The sensor element is a ceramic cylinder plated inside and out with porous platinum electrodes; the whole assembly is protected by a metal gauze. It operates by measuring the difference in oxygen between the exhaust gas and the external air, and generates a voltage or changes its resistance depending on the difference between the two. The sensors only work effectively when heated to approximately 300°C, so most newer lambda probes have heating elements encased in the ceramic to bring the ceramic tip up to temperature quickly when the exhaust is cold. The probe typically has four wires attached to it: two for the lambda output, and two for the heater power, although some automakers use a common ground for the sensor element and heaters, resulting in three wires. Earlier non-electrically-heater sensors had one or two wires"
"It operates by measuring the difference in oxygen between the exhaust gas and the external air,"
"The sensor element is a ceramic cylinder plated inside and out with porous platinum electrodes; the whole assembly is protected by a metal gauze. It operates by measuring the difference in oxygen between the exhaust gas and the external air, and generates a voltage or changes its resistance depending on the difference between the two. The sensors only work effectively when heated to approximately 300°C, so most newer lambda probes have heating elements encased in the ceramic to bring the ceramic tip up to temperature quickly when the exhaust is cold. The probe typically has four wires attached to it: two for the lambda output, and two for the heater power, although some automakers use a common ground for the sensor element and heaters, resulting in three wires. Earlier non-electrically-heater sensors had one or two wires"
"It operates by measuring the difference in oxygen between the exhaust gas and the external air,"
Brian
01-30-2008, 02:02 PM
#18
Nordschleife Master
"Right, so there are two sensing elements."
Just one I think . On one side is the the gas being measured and the other side is the reference .
The inside side of the O2 sensor is open to the out side air . The outside side of the O2 sensor is in the exhaust stream .
In the past the vent for the inside of the O2 sensor was near the sensor , it was exposed to everything kicked up by the tires . Now the vent to the inside of the O2 sensor is via the wires . The end of the wires are protected inside the engine tin work , hopefully a cleaner / drier place that will keep the inside of the O2 sensor from "seeing" much contamination .
Anybody have an old dead O2 sensor ?
I'd now like to disassemble one .
Just one I think . On one side is the the gas being measured and the other side is the reference .
The inside side of the O2 sensor is open to the out side air . The outside side of the O2 sensor is in the exhaust stream .
In the past the vent for the inside of the O2 sensor was near the sensor , it was exposed to everything kicked up by the tires . Now the vent to the inside of the O2 sensor is via the wires . The end of the wires are protected inside the engine tin work , hopefully a cleaner / drier place that will keep the inside of the O2 sensor from "seeing" much contamination .
Anybody have an old dead O2 sensor ?
I'd now like to disassemble one .
01-30-2008, 07:55 PM
#21
Racer
Thread Starter
Couple of points-correct me if I am wrong
The difference between the Porsche sensor and the universal sensor is the Porsche sensor comes with the plug connected. No splicing required but it cost about double the price. Also for me the Porsche sensor was ex Germany.
My sensor comes with 3 wires - 2 white (the heating element) and 1 black (the sensor). It does not matter what way the white wires go but black must go to black on the plug. Even I got this correct
The difference between the Porsche sensor and the universal sensor is the Porsche sensor comes with the plug connected. No splicing required but it cost about double the price. Also for me the Porsche sensor was ex Germany.
My sensor comes with 3 wires - 2 white (the heating element) and 1 black (the sensor). It does not matter what way the white wires go but black must go to black on the plug. Even I got this correct
02-17-2008, 04:50 PM
#23
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An oxygen sensor is a comparitive device. It compairs the concentration of oxygen in the exhaust to the concentration of oxygen in the ambient air. It needs two sources of Oxygen. One is the measurement which is taken from the exhaust, and the other is "reference air", which in the case of a Bosch sensor, is taken from the spaces between the wire strands.
02-19-2008, 08:34 PM
#24
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This topic left me curious enough to do a search.
I had never heard this before. So I guess you learn something new every day.
Kirk
Some oxygen sensors use the wiring (actually sheet on wiring) as a channel for reference oxygen. If you cut off the connector, solder and shrink-wrap, you may be blocking reference oxygen.
You should never solder a O2 sensor wire because the sensor "will breathe" through the cable. The acceptable method of splicing or repairing O2 wiring is with crimp connectors. This information was from Bosch Technical Staff in Europe. Here is the technical description of why you do not solder the connections on the O2 sensor side of the updated wiring.
The outside of the bulb is exposed to the hot gases in the exhaust while the inside of the bulb is vented internally through the sensor body to the outside atmosphere. Older style oxygen sensors actually have a small hole in the body shell so air can enter the sensor, but newer style O2 sensors "breathe" through their wire connectors insulation and have no vent hole.
It's hard to believe, but the tiny amount of space between the insulation/wire and through wire insulation provides enough air to seep into the sensor (for this reason, grease should never be used on O2 sensor leads/connectors because it can block the flow of air). Venting the sensor through the wires rather than with a hole in the body reduces the risk of dirt or water contamination that could foul the sensor from the inside and cause it to eventually fail.
The outside of the bulb is exposed to the hot gases in the exhaust while the inside of the bulb is vented internally through the sensor body to the outside atmosphere. Older style oxygen sensors actually have a small hole in the body shell so air can enter the sensor, but newer style O2 sensors "breathe" through their wire connectors insulation and have no vent hole.
It's hard to believe, but the tiny amount of space between the insulation/wire and through wire insulation provides enough air to seep into the sensor (for this reason, grease should never be used on O2 sensor leads/connectors because it can block the flow of air). Venting the sensor through the wires rather than with a hole in the body reduces the risk of dirt or water contamination that could foul the sensor from the inside and cause it to eventually fail.
Kirk
