conversion to ppm for methane sensor
some students of mine made methane sensor mq 4. how tried convert analog values ppm:
since closest thing known methane value that had available straight natural gas coming through line valve in chemistry lab @ school, used sample represent saturation value (in other words, million ppm). read average commercial natural gas supplied 96 percent pure, let saturation count 960000 ppm. analog read value sensor next valve (as saturated it) 690. the lowest analog read value got 38.
since data sheet mq4 says it's base 10 logarithmic, how they came conversion:
960000=10k(690-38) or max val ppm= 10 k (max analog read-min analogread)
log 960000 = k(652)
log960000/652 = k = .009
so final formula converts analog read ppm based on formula:
y= 10 .009(x-38) x being analog read value
they know full if formula more correct using gas valve in lab @ best crude calibration standard.
has out there tried such value conversion gas sensors? i'm not math guy, make sense.
since closest thing known methane value that had available straight natural gas coming through line valve in chemistry lab @ school, used sample represent saturation value (in other words, million ppm). read average commercial natural gas supplied 96 percent pure, let saturation count 960000 ppm. analog read value sensor next valve (as saturated it) 690. the lowest analog read value got 38.
since data sheet mq4 says it's base 10 logarithmic, how they came conversion:
960000=10k(690-38) or max val ppm= 10 k (max analog read-min analogread)
log 960000 = k(652)
log960000/652 = k = .009
so final formula converts analog read ppm based on formula:
y= 10 .009(x-38) x being analog read value
they know full if formula more correct using gas valve in lab @ best crude calibration standard.
has out there tried such value conversion gas sensors? i'm not math guy, make sense.
the math looks right.
they might able better estimate of high end of range using balloon. put sensor in balloon , squeeze balloon down around sensor air out. attach gas outlet , partially fill balloon gas take reading. needless - no smoking ]
that ought close top end. it'll quite bit higher 690 can plug new value formula derive k , away go.
pete
they might able better estimate of high end of range using balloon. put sensor in balloon , squeeze balloon down around sensor air out. attach gas outlet , partially fill balloon gas take reading. needless - no smoking ]
that ought close top end. it'll quite bit higher 690 can plug new value formula derive k , away go.
pete
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