Spurious Gas Alarms

[nigelmercier]

Being very sensitive to temperature you'd expect some form of reference measurement so that allowance was made for changes in ambient temperature.

They do, it's called a Wheatstone bridge. They have two sensor cells, but only one is exposed to the atmosphere. If the latter cells detects gas, it unbalances the bridge and produces a reading. If you look at the link on Wikipedia, then R2 and Rx are the sensors. Note that this example uses resistors, but is valid for any sensor.

 

[VicS]

They do, it's called a Wheatstone bridge. They have two sensor cells, but only one is exposed to the atmosphere. If the latter cells detects gas, it unbalances the bridge and produces a reading. If you look at the link on Wikipedia, then R2 and Rx are the sensors. Note that this example uses resistors, but is valid for any sensor.

Yes . I dont need Wikipedia to explain what a Wheatsone bridge is thank you very much.

 

[nigelmercier]

Yes . I dont need Wikipedia to explain what a Wheatsone bridge is thank you very much.

Perhaps not, but others may be interested.

 

[VicS]

Perhaps not, but others may be interested.

Everybody learnt what a Wheatstone bridge is at school!

 

[greenalien]

Everybody learnt what a Wheatstone bridge is at school!

Everyone who studied GCE Physics or Electronics, maybe...