Strange analogue input behaviour at zero volts

[fast_grandad]

As a cheap and cheerful way of logging braking I've simply connected the brake light switch to one of the analogue inputs. The voltage switches between zero at brakes-off to battery voltage (+12 'ish) at brakes on. The analogue input is effectively grounded by the brake lights (incandescent bulbs) when the brakes are off.

When played back through the Analysis software, the graph and listed data go to 12V at brakes-on but, on brakes-off, only go back to zero briefly and the voltage then appears to be integrated, i.e. it ramps back up to 12Volts.

Its definitely not a problem with the LC1 not reading zero volts as Monitor Lite displays the voltage correctly in real-time and a voltmeter connected to the analogue input show the voltage as being hard switched between zero and 12V.

Does the analysis software have a problem with an analogue input of zero volts? I can put some sort of diode/resistor catching circuit in if necessary but I can't believe it should be.

[Support]

Can you send me a sample data set please so I can have a closer look? gummi(at)race-technology.com