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ostaquet / Arduino-MQ131-driver

Arduino driver for gas sensor MQ131 (Ozone / O3)
MIT License
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the time required to heat up the resistance #34

Closed ChanGarciaV closed 3 years ago

ChanGarciaV commented 3 years ago

Hi, I have a question, what happens if I want to take measures quickly, can I turn on the resistor permanently? If I can do that what are the issue with turn on the resistor heater permanently?

ostaquet commented 3 years ago

Hi @ChanGarciaV,

It is not a good idea to keep the heater powered all the time because the sensor is semiconductor gas sensor. Basically, the Rs (resistance of the sensor) is changing depending on the gas molecules burned at the surface.

If you keep the heater on all the time, you will never measure anything because the gas molecule will be burned continuously. To have a reliable reading, you have to wait between two samples that the heater is cold again.

KR, Olivier

lackdaz commented 2 years ago

Thanks for the clear explanation, I was also wondering why you were powering down the heater when the preheat time was recommended to be 48hr. This is indeed very misleading.

Can you share sources of where you found out about this?

ostaquet commented 2 years ago

@lackdaz The pre-heat (burn-in) is a one-shot operation to perform. It is required to burn the chemicals that are on the sensor when it comes out of factory.

The heating time (at each measurement) is another story. It is required to generate the chemical reaction of burning particles of gas. Check out https://en.wikipedia.org/wiki/Gas_detector#Semiconductor for more info about how it behaves theoretically. So, the heating at the measurement must be stopped to perform the measurement ;-).