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Perhaps my post awoke crutschow to complete his circuit.
You might be tempted by the simplicity of my circuit Vs that offered by crutschow; however I doubt the design issues with my circuit can be overcome.
It would be fairly easy to completely stop the integrator circuit when the engine is not running (and any biasing effects), but the self-discharge of the capacitor will cause too great an error.
Tantalum capacitors might have an internal dc leakage of the order of a nA – but the voltage losses over time (a day) will be enormous.
Even replacing C1 by an ultra-capacitor of 1F (allowing R1 to be reduced by a factor of 100) will not solve the problem. Typically such capacitors loose around 50mV of their charge voltage/day, resulting in the addition of half a litre of fuel/day to the tank – with the car just sitting on your drive.
You might be tempted by the simplicity of my circuit Vs that offered by crutschow; however I doubt the design issues with my circuit can be overcome.
It would be fairly easy to completely stop the integrator circuit when the engine is not running (and any biasing effects), but the self-discharge of the capacitor will cause too great an error.
Tantalum capacitors might have an internal dc leakage of the order of a nA – but the voltage losses over time (a day) will be enormous.
Even replacing C1 by an ultra-capacitor of 1F (allowing R1 to be reduced by a factor of 100) will not solve the problem. Typically such capacitors loose around 50mV of their charge voltage/day, resulting in the addition of half a litre of fuel/day to the tank – with the car just sitting on your drive.
