thx again, and i have checked immediately, i have gaineded steady voltage reading, and i have also checked the data sheet, http://www.winsensor.com/english/products/sms/jsq.asp?filename=MQ7.pdf
, so, i am sure i am supplying 5.2 - 5.4 voltage to the circuit correctly, and the readings are still not ok ...
btw, is it necessary to pre-heat this sensor? i have found one point in the datasheet saying that it takes 2 days to re-heat the sensor,
so does it mean i have to supply 5 volt to the circuit for 2 days for reasonable readings?
sorry, i have a fairly ok knowledge only, thx for your patience, thxthxthx