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air flow sensor - diy hot wire air flow circuit

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nvp

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Hello Friends..
Does any one has idea HOW AIR FLOW SENSOR works? Also if any one has circuit , Let me know u have..
Regards
NVP
 

sadat007

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air flow sensor

It can be like a fan with dc motor, or it can be two temperature sensors on effected by air flow one dose not.
 

techie

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thermistor air flow pic

Air flow sensor can be designed using 2 thermistors. One measuring the ambient temperature and the other is maintained at an elevated temperature. The power required to keep the temperature constant is related to the ambient temperature and the air flow over the thermistor.
 

dudu

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air flow rate sensor pdf

you can see some papers from TUDELFT, they have a fully integrated flow sensor now are availlable in the market.
 

nvp

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how to measure air flow sensor

Hi Techie
Do u have any reference shematic of the same?
Yep, Why we need two thermisters? One is enoug right? Why can't we fix one as variable or fixed value resistor? Other one is thermistor.
Is that makes sence??
regards
NVP
 

nvp

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airflow termistor

dudu said:
you can see some papers from TUDELFT, they have a fully integrated flow sensor now are availlable in the market.
Can u pls send me some URLs
Regards
NVP
 

wolf69

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thermistor airflow

you can use ultrasoud too. in case of hot hair flow the two-termistor mode is not precise.
bye
 

techie

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ultrasonic airflow sensor

You need 2 thermistors because 1 is used to measure the ambient temperature since the power required to maintain the other thermistor at a constant temperature will be highly dependent on ambient temperature.

In order to maintain the 2nd thermistor at constant Temperature, you just have to measure its resistance and heat it up so that its resistance maintains a certain value.
 

flatulent

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seminar topics on air mass flow sensor

The air humidity also controls the heat loss in the wind. If you want to be very accurate, you will also have to measure the humidity and make a correction for this.

The heat loss vs wind is very nonlinear. This method works best for low velocity. Use the propeller or anemometer (cups at the end of spokes) method for higher velocities.
 

techie

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flow sensor circuit using a thermistor

Flatulent is right. The method I described is only usefull if the air-flow is quite low. This method is also not very accurate since humidity and non-linearity are both a factor to consider. But at these rates of flow, measurement using mechanical methods become very expensive or inaccurate. If you are measuring high wind speeds, better go for mechanical.
 

purloiner

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anemometre 16f84

The method using two thermistors is referred to as Thermal Mass Flow and companies like Endress + Hauser make an exremely accurate instrument unsing this technology, called T-Mass...

It's used in application where the mass flow of a specific gas needs to be measured... As long as the device is calibrated the device can be programmed to any one gas but, it isn't possible to measure more than one different gas with one meter because, the thermal expansion coefficeints of the various gasses arn't always the same, actually they[re never the same...

Once the device has been calibrated and linearized for the specific gas, only moisture can affect its accuracy...
 

Trishool

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www.linear.com/pdf/an43.pdf

Hi,

EdnMag , reed electronics articles are full at google do a little search . Basicall you require to heat some thermistor and when air flows over it you measure the resistance ! . But be carefull about ambient temperature you will also require one reference thermistor which in some designs you wont find .

good luck
 

techie

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mass air flow sensor build light bulb

Thanks for the file but to conserve bandwidth, please avoid BMP file. The same file converted to GIF is only 18kb. Pls find attached
 

Fragrance

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air flow sensor build light bulb ultrasonic

hi

here is the some thing from me air flow sensor programable type pic 16f84 based design with lot of paarameters may this also help you to design your own
 

chrhuy

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thermistors+air flow sensor

Not all systems work with resistors, if i am correct, the automotive
air flow sensors do not...
they work with a constant heating element and measure the amount of cooling...
A guy once told me, that some of them use a very thin wire, like a light bulb, so when they place a voltage onto it, it starts to glow, and with less or more cooling the resistance of the wire changes, and so they can measure the current flowing through it...
Don't know it for sure, but seems to make sense...
Hope this helps you a little..

Chrhuy.
 

W49N3R

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air flow sensor bmp

It is imperative to understand exactly the environment where the sensor will be used.

There are different characteristics in each environment, and different sensors more appropriate for each one.

In most cases, measuring the diference in temperature (twin thermal elements), one exposed the other don't, is enough to measure how much heat was removed from the exposed, but it is not very linear and depends on ambient effect.

An effective way is by moving a rotor, but requires a certain volume of air to be someway more precise. Sometimes using two different techniques is better.

One should always remember that for the right job there is a right tool, same way here.

Wagner.
 

darciok

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airflow sensor 16f84

I found this...I think it's quite good circuit on pic..
 

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