Talk:Mass flow sensor

This should most definitely not be merged with Air flow meter. In fact Vane style meters needs to be removed from this section. It's already bad enough that everyone in the car world think that an AFM and a MAF are the same thing. The last thing people need is something supporting that. This is my first time contributing to Wikipedia so I don't know etiquette otherwise I would make changes myself.

Vane style meters measure volumetric flow rate. They are not mass flow sensors they are volumetric flow sensors. Used in conjunction with a MAP sensor and a temp sensor they could be used to calculate mass flow rate but they are very often only used with a temp sensor and sometimes not even that. Without those it cannot calculate mass airflow. — Preceding unsigned comment added by Yoshimitsuspeed (talk • contribs) 02:07, 12 March 2015 (UTC)

This article should be merged with "Air flow meter"
The two are closely related... I think they should be merged into one. I think the name "Air flow meter" is best for merging both under, so anyone want to copy the stuff over? —Preceding unsigned comment added by HonzaTheOptional (talk • contribs) 10:04, 1 August 2009 (UTC)

There are many many uses for mass flow sensors outside of automotive, including industrial automation and scientific instruments. Irelandmc (talk) 14:22, 13 September 2013 (UTC)


 * This should most definitely not be merged with Air flow meter.
 * In fact Vane style meters needs to be removed from this section. It's already bad enough that everyone in the car world think that an AFM and a MAF are the same thing. The last thing people need is something supporting that. This is my first time contributing to Wikipedia so I don't know etiquette otherwise I would make changes myself.


 * Vane style meters measure volumetric flow rate. They are not mass flow sensors they are volumetric flow sensors. :Used in conjunction with a MAP sensor and a temp sensor they could be used to calculate mass flow rate but they are very often only used with a temp sensor and sometimes not even that. Without those it cannot calculate mass airflow.  — Preceding unsigned comment added by Yoshimitsuspeed (talk • contribs) 02:07, 12 March 2015 (UTC)

Updates
It looks like it has been a while since the page was updated. I was doing some research, and did some more after finding this page, on the MAF on my car and came across a term that i don't see on this page but which is in a fair bit of use in the automotive industry. The type of MAF is called a Karman Vortex MAF. It works by setting up and then disrupting a laminar air stream which is then read by the sensor. Information can be found here: http://www.autoshop101.com/forms/h34.pdf Instead of outputting a constant voltage modified by a resistance factor, this type of MAF outputs a frequency which must then be interpreted by the ECU. This type of MAF can be found on second generation DSMs (mitsubishi eclipse, eagle talon) and some toyota's and lexuses. The general concept is that a laminar airflow is set up, then disrupted by a vertial bow in the sensor, this causes wake in the air and subsequently the wake will collapse and cause karman vortexes. These vortexes can either be read directly as a pressure pulse against a sensor, or they can be made to collide with a mirror with will then interupt or transmit a reflected light beam to generate the pulses in response to the vortexes. The first kind can only be used in pull thru air (prior to a turbo or supercharger) while the second kind could theoretically be used push or pull thru air (before or after a forced induction application like the previously mentioned super or turbo charger).

Thats about all i had on that. Hopefully someone else with a bit more finesse can add this information to the page in a manner that doesn't destroy its already reasonable cleanliness and readability. ^_^ --Takophiliac (talk) 20:25, 14 August 2008 (UTC)


 * Merged a couple versions of automotive mass air flow articles into one, and joined them under the more generic article of mass flow sensor. Sattyam 23:55, 21 May 2006 (UTC)

VZ commodore does not use hotwire
VZ and later commodore's use a "coldwire" MAF system where by the air passing over a tiny sensor causes inductance, this inductance is converted to a frequency which is then fed to the car's ECU. This frequency is related to the amount of air (CFM) passing over the unit.

The mesh on the MAF is used to smooth out airflow to ensure the sensors get the best chance to get a steady reading.

CORRECTION: The cold wire sensor does not measure inductance of air. The inductance of air can be affected by any number of contaminants or conditions, such as humidity, gas vapors or particulate matter. A Cold air sensor is simply a design that uses a cold wire (non heated) element to measure air temperature coming into the sensor as well as a heated wire in order to correct for changes in air density and temperature having an effect on the output. More information: http://www.kemparts.com/TechTalk/tt06.asp

Correction needed: " Manufacturers claim that a simple but extremely reliable test to ensure correct functionaldiscarded and an OEM replacement installed."

Hot wire sensor
Currently we have, The amount of current required to maintain the wire’s electrical resistance is directly proportional to the mass of air flowing past the wire. Unless it is made of some sort of magical material that has infinite resistance when there is no air flow, that can't be right. Directly related I would believe, and maybe even linearly related, but not directly proportional. Aij 03:59, 6 September 2007 (UTC)

Hot Wire Sensor: this is false (backwards) "The wire's temperature increases with the wire’s electrical resistance, which limits electrical current flowing through the circuit. When air flows past the wire, the wire cools decreasing its resistance, which in turn allows more current to flow through the circuit. As more current flows, the wire’s temperature increases until the resistance reaches equilibrium again."

Should read: "The wire's temperature DEcreases with the wire’s electrical resistance" --75.18.117.165 03:36, 24 October 2007 (UTC) deleted stuff.


 * "When air flows past the wire, the wire cools decreasing its resistance, which in turn allows more current to flow through the circuit. As more current flows, the wire’s temperature increases until the resistance reaches equilibrium again." http://www.autoshop101.com/forms/h34.pdf  75.18.117.165 03:52, 24 October 2007 (UTC)


 * Also, if the resistance reached equilibrium the current flow and thus the voltage would never change... how would the control unit be able to detect changes in mass? 75.18.117.165 03:36, 24 October 2007 (UTC)

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What is the unit of measure for a MAF using OBD II?
On occasion I watch Youtube videos like GMC Truck - Running Lean P0171 & P0174. The diagnosis often examines the MAF sensor readings. The OBD II MAF sensor data at idle should be approximately the engine displacement. For example, a 3.3 liter engine should have an MAF idle reading of 3.3 g/s.

In the GMC Truck - Running Lean P0171 & P0174 video at the 3:27 time mark, the ODB II test equipment shows the MAF sensor reading 23.21 g/s at 1210 RPM.

My question is (the reason I visited this wiki page), what are the units? What is "g/s"? Is it gallons/second? Is it grams/second? Something else?

Jeffrey Walton (talk) 06:33, 31 October 2020 (UTC)

Contradiction in page
The summary notes: "There are two common types of mass airflow sensors in use on automotive engines. These are the vane meter and the hot wire. Neither design employs technology that measures air mass directly." However, in the Hot Wire section, the article says: "If air density increases due to pressure increase or temperature drop, but the air volume remains constant, the denser air will remove more heat from the wire indicating a higher mass airflow. Unlike the vane meter's paddle sensing element, the hot wire responds directly to air density. This sensor's capabilities are well suited to support the gasoline combustion process which fundamentally responds to air mass, not air volume." This indicates to me that the hot wire method does indeed directly measure air mass. I am not knowledgeable enough about this subject to feel confident in editing the topic, but wanted to bring attention to it for someone who is.