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Jun 24, 2019 · For most of us, Oxygen sensors (also known as a Lambda or O2 sensor) are a little bit 'out of sight out of mind'.However, the sensor is vital part of the ove...
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May 21, 2020 · Oxygen sensors are devices used by vehicles to monitor emissions when paired with a catalytic converter. They’re also used to measure how rich or lean combus...
Oxygen Sensor | How Oxygen Sensor WorksIn this video, we delve into the fascinating world of oxygen sensors. Often referred to as O2 sensors, these vital com...
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An oxygen sensor is an electronic device that measures the proportion of oxygen in the exhaust gasses exiting an engine. Located in the exhaust system, it provides real-time data to the vehicle’s Engine Control Unit (ECU), which uses this information to adjust the air-fuel mixture for optimal combustion.
- Introduction
- Oxygen Saturation
- Physical Properties Used in Pulse Oximetry
- Calibration Adjustment
- Pulse Oximeters Measure Pulsatile Blood
- The Signal Is Really Small !
- Plethysmographic Trace
- Light Source
- Accounting For Ambient (Room) Light
- Problems with Pulse Oximeter
Pulse oximeters measure how much of the hemoglobin in blood is carrying oxygen (oxygen saturation). If you work in healthcare (or have been patient !) you are very likely to have come across pulse oximeters. You can find them in areas such as operating rooms, recovery, critical care, wards, and ambulances. Pulse oximeters are in common use because ...
Pulse oximeters measure oxygen saturation. Before we learn the principles of how pulse oximeters work, we need to have an understanding of what oxygen saturation is. We all know that we need oxygen for life. ( Some of you may find this section a little too basic. In that case, to skip this short section, click this link to go to next section Physic...
Pulse oximetry uses light to work out oxygen saturation. Light is emitted from light sources which goes across the pulse oximeter probe and reaches the light detector. If a finger is placed in between the light source and the light detector, the light will now have to pass through the finger to reach the detector. Part of the light will be absorbed...
Early on , we discussed how the pulse oximeter uses Beer’s and Lambert’s Law ( absorbance depends on concentration and path length) as part of its factors that it uses to compute oxygen saturation. Unfortunately, there is a problem. In physics, the Beer and Lambert law have very strict criteria to be accurate. For an example, the light that goes th...
In a body part such as a finger, arterial blood is not the only thing that absorbs light. Skin and other tissues also absorb some light. This poses a problem , because the pulse oximeter should only analyse arterial blood while ignoring the absorbance of light by surrounding tissues. For an example of how tissues can interfere, take the two situati...
The diagrams used so far have exaggerated the size of the pulsatile part to make it easy for you to see and understand. However, in reality, the pulsatile signal is very small. Typically , only about 2 % of the total signal is pulsatile ! Drawn to scale, 2 % of the total signal will look like the diagram below. The orange part represents the “non c...
Pulse oximeters often show the pulsatile change in absorbance in a graphical form. This is called the “plethysmographic trace ” or more conveniently, as “pleth”. The pleth is an extremely important graph to see. It tells you how good the pulsatile signal is. If the quality of the pulsatile signal is poor, then the calculation of the oxygen saturati...
Pulse oximeters use a type of light source called “light emitting diodes” (LED) which are extremely commonly used in electronics. Light emitting diodes are ideal for pulse oximeters as they : 1. Are cheap ( so can be used even in disposable probes) 2. Are very compact (can fit into very small probes) 3. Emit light in accurate wavelengths 4. Do not ...
The pulse oximeter probe, as shown below, has a red LED and one infrared LED. On the other side, is a light detector. However, you will note that, though there are only two LEDs, the light detector is exposed to three sources of light. In addition to the red and infra red LED light sources, there is also light in the room (ambient light) that the p...
Problem of movement
When you think of problems associated with pulse oximeters it is important to remember that the signal that is analyzed is really tiny. As explained before, it is only about 2 % of the total light that is analyzed. Which such a small signal, it is easy to see how errors can occur. Pulse oximeters are very vulnerable to motion, such as a patient moving his hand. As the finger moves, the light levels change dramatically. Such a poor signal makes it difficult for the pulse oximeter to calculate...
Problem of optical shunting
The pulse oximeter operates best when all the light passes through arterial blood, as shown in the upper finger in the image below. However, if the probe is of the wrong size or has not being applied properly, some of the light , instead of going through the artery, goes by the side of the artery (shunting)(lower finger in image below). This reduces the strength of the pulsatile signal making the pulse oximeter prone to errors. It is therefore important to select the correct sized probe and t...
Problem of too much ambient light
As discussed before, in addition to the light from the LEDs, ambient (room) light also hits the detector. For good functioning of the pulse oximeter, the strength of the LED light falling on the detector should be good when compared with the strength of the ambient light falling on the detector. If the ambient light is too strong, the LED light signal gets “submerged” in the noise of the ambient light. This can lead to erroneous readings. Therefore, it is important to minimise the amount of a...
Jan 6, 2023 · The cost to replace an oxygen sensor ranges from $155-$500, depending on if you DIY or go to a shop. You can check out our full cost guide here. You can test the oxygen sensor at home with a voltmeter or OBD2 scan tool like the FIXD Sensor. Go to the live data feed within the FIXD app to see the voltage and response time of your O2 sensors.
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What's inside of an oxygen sensor? How do they work? A brief overview of what's actually going on inside of an oxygen sensor. For more information and to fi...
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