How to calibrate an alcohol meter?

[KamW]

Hi

I am going to make meter which could measure ethanol concentration in breath air. I am wondering how could I calibrate such meter.
Of course method with volunteer for drink vodka is very good, but what if I would like to calibrate for instance 5 promiles?

regards
KamW

 

[flatulent]

alcohol meter

There is probably some way of putting the alcohol in a large plastic bag and blowing up the bag and closing the opening. Wait for the alcohol to evaporate. From the volume of the bag and of alcohol you should be able to calculate the concentrationl

 

[KamW]

alcoholmeter

Thx flatulent for your response.

The first problem was how much ethanol should be used in the bag - if It would be decided to use bags. For investigation purposes I have used permeation devices or often diffusion vials for generation of gas atmosphere. All was controled by MFC's But now I am looking for simple method how to calibrate our sensor, when it will be on the market.

The amount of alcohol in the blood is the mass fraction of the blood - promile or BAC. in air there is ppm or mg/dm3 - it is fraction of the vapour in gas absolutelly different than in the blood.

The second problem is that for calibration of semiconductor sensor there is need to use the same concentration, humidity, temperature and especially flow rate as in the breath.


regards
KamW

 

[eirp]

alcohol promiles

Thx flatulent for your response.

The first problem was how much ethanol should be used in the bag - if It would be decided to use bags. For investigation purposes I have used permeation devices or often diffusion vials for generation of gas atmosphere. All was controled by MFC's But now I am looking for simple method how to calibrate our sensor, when it will be on the market.

The amount of alcohol in the blood is the mass fraction of the blood - promile or BAC. in air there is ppm or mg/dm3 - it is fraction of the vapour in gas absolutelly different than in the blood.

The second problem is that for calibration of semiconductor sensor there is need to use the same concentration, humidity, temperature and especially flow rate as in the breath.


regards
KamW

KamW, I agree with you - there's need to approach real conditions.
Lend a professional product, make a party with few volunteers for which you buy a good vodka.
You need to calibrate your meter with professional one and for higher amount of promiles (say 2+) you should do extrapolation from gained data.
In my opininon, professional meters must use some built-in transform functions which transfers promiles in blood to concentration in air in mg/dm^3
If you live near me, I'm ready to become a volunteer in your experiment :twisted:

Best regards,

eirp

 

[PaulHolland]

alcohol promile

Maybe this is a way:

Take a baloon, fill it with a small amount of pure 80% alcohol. fill the baloon with air. and measure the radius of the baloon. from this you can calculate the volume.

Connect the baloon to the DUT and let the air escape from the baloon...
Then take a calibrated alcohol test device and see what the result is. now you can compare the results and use this to calibrate your own test device...

what do you think ???..

Paul.

 

[KamW]

promille meter

eirp thx for your volunteer, but i hope there will be 1k pcs of sensor per month to calibrate, so I am not sure if your liver and especially lungs could mange callibrations. Assuming two points callibration, and next veryfication of parameters it would be a lot of breath. It would be really hard work to do. ;-)

Yes there is special formula for calculation of BAC to mg/dm3. I have found it yesterday -

[BAC] div by 1500 to 2600 = [mg/dm3]

where coefficient depends of the person

PaulHolland good point, except of the speed and temperature of gas. From the bag it would be uncomparable with human breath. And of course humidity of such air will be different than breath one. It is not a problem with IR sensor, but we have made SnO2 sensor, which are very sensitive on humidity. (In this application it is not problem because human breath has always near constant temperature and humidity)

Finally it could be very usefull!!
I've found the article, the author said that change of temperature of part of degree - for instance fast, deep breath of 20s could change (decrease !!!) result of police alcohol breath meter response of 12% !!!
Maybe someone could test it empirically?? Every information very appreciated

regards
KamW

 

[salamander]

breath air alcohol blood ppm

Hello,
while I'm thinking of this topic as my "skilled work" in physics (I think, this topic is quite interesting, as it has an real life importance and of course has much to do with phsics/chemistry/biology and I can also do some practical work like building a simple sensor application) I would like to know if you have some information about how such a sensor could work (what kind of sensor can we use?).

thanks for all help

salamander

 

[KamW]

convert ppm to promilles

Hi salamander

There are a lot of sensor could be used. Proffesional (quite expensive) solution is to use infra red sensor. for low cost solution you could use semiconductor sensors, doesn't matter for which gas, most of sensors are sensitive for alcohol (so called crossensitivity).
The best solution (future) it is fuell cell. It is still expensive, but in near future in my oppinion it will be the only solution for alcohol meter.

It is very interesting topic not only for skilled work, it could be topic for PhD. I am working in the field of gas sensor, and till now for alcohol meter we have graduated 2 MSc and there is a lot of work to do - there is a lot of work to use neural network, fuzzy logic and etc in the field of sensors.

The one who would be able to sell cheap, stable, sensitive, and especially selective sensor will win a lot on the market.
I don't know if you have ever thought why haven't you had gas sensor in your house? (or why most of peoples have not?).

regards
KamW