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michaelk  
#1 Posted : 10 September 2018 10:12:28(UTC)
michaelk

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HI I'm working on MQ gas sensors

when i put this sensor in vacuum chamber i expected the sensor to read low ADC since there is no gas
but actually it reads high
when the vacuum reduces to 0.05 mbar it goes to peak and reaches saturation (reads 1023)

why is this
when no gas it should read zero

can any one help?

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Edited by user 10 September 2018 10:15:33(UTC)  | Reason: Not specified

chariotadmin  
#2 Posted : 10 September 2018 10:14:06(UTC)
chariotadmin

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Nonsense. Please read the sensor data sheet and study the excellent tutorial here.

These sensors are really only useful for measuring a change in the gas mixture, and they must be "burned in" for 24 to 48 hours before any use.
michaelk  
#3 Posted : 10 September 2018 10:16:36(UTC)
michaelk

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You didnt get my question I have done all the perquisites the sensor can detect the gas in the environment subjected and also responds well for different concentration of gas. there is no problem about its working but when I put this mq gas sensor in vacuum chamber and subject it to vacuum the sensor reads high value

The vacuum chamber does not have any gas inside then the gas sensor should have RS/RO ratio large

which in datasheet represents a low concentration

but the sensor reads a high concentration value when the sensor it subjected to vacuum which should read a low value but I'm getting it high in absence of gas in vacuum

why is this

can the sensor be operated in vacuum

what happens to the behaviour of the sensing element when in vacuum

why is the sensor reading high in vacuum when gas is absent
skoufis  
#4 Posted : 10 September 2018 10:17:46(UTC)
skoufis

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Cyprus

As your test clearly shows, your assumption that the reading should be zero in a vacuum is incorrect.

"can the sensor be operated in vacuum"
Yes, it can. But it makes no sense to do so.

These sensors must be individually calibrated using known concentrations of the gas you want to detect, in dry air at normal atmospheric pressure. See the datasheet for the details.
michaelk  
#5 Posted : 10 September 2018 10:18:05(UTC)
michaelk

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thank you for your information

ill get back to you
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