<P> Note that this equation, unlike the equation for the basic dual - slope converter, has a dependence on the values of the integrator resistors . Or, more importantly, it has a dependence on the ratio of the two resistance values . This modification does nothing to improve the resolution of the converter (since it doesn't address either of the resolution limitations noted above). </P> <P> One method to improve the resolution of the converter is to artificially increase the range of the integrating amplifier during the run - up phase . As mentioned above, the purpose of the run - up phase is to add an unknown amount of charge to the integrator to be later measured during the run - down phase . Having the ability to add larger quantities of charge allows for more higher - resolution measurements . For example, assume that we are capable of measuring the charge on the integrator during the run - down phase to a granularity of 1 coulomb . If our integrator amplifier limits us to being able to add only up to 16 coulombs of charge to the integrator during the run - up phase, our total measurement will be limited to 4 bits (16 possible values). If we can increase the range of the integrator to allow us to add up to 32 coulombs, our measurement resolution is increased to 5 bits . </P> <P> One method to increase the integrator capacity is by periodically adding or subtracting known quantities of charge during the run - up phase in order to keep the integrator's output within the range of the integrator amplifier . Then, the total amount of artificially - accumulated charge is the charge introduced by the unknown input voltage plus the sum of the known charges that were added or subtracted . </P> <P> The circuit diagram shown to the right is an example of how multi-slope run - up could be implemented . The concept is that the unknown input voltage, V i n (\ displaystyle V_ (in)), is always applied to the integrator . Positive and negative reference voltages controlled by the two independent switches add and subtract charge as needed to keep the output of the integrator within its limits . The reference resistors, R p (\ displaystyle R_ (p)) and R n (\ displaystyle R_ (n)) are necessarily smaller than R i (\ displaystyle R_ (i)) to ensure that the references can overcome the charge introduced by the input . A comparator is connected to the output to compare the integrator's voltage with a threshold voltage . The output of the comparator is used by the converter's controller to decide which reference voltage should be applied . This can be a relatively simple algorithm: if the integrator's output above the threshold, enable the positive reference (to cause the output to go down); if the integrator's output is below the threshold, enable the negative reference (to cause the output to go up). The controller keeps track of how often each switch is turned on in order to estimate how much additional charge was placed onto (or removed from) the integrator capacitor as a result of the reference voltages . </P>

The start of conversion of adc is identified when