I have built 12VDC circuit that uses a comparator to make decisions based on the intensity of a certain voltage, whose variation is due a resistance change. The problem is that this resistance varies very little (a maximum maximorum of 1%, but most of the time much less).
The problem is that my comparator has a 3mV offset, which means that changes smaller than that do not trigger my comparator. Once 3mV is 0,025% of 12V and a Wheatstone bridge gives ∆V/V ≈ (∆R/R)/4, then the minimum resistance variation I can measure is 4*0,025%=0,1%, which is only 1/20 of the total variation. In other words, I have a 5% error measurement. What can I do to improve that number (even by a factor of 2) apart from using an amplifier? Are there comparators with smaller offsets (at erasonable prices)? A tension multiplier could do the trick?
Note: all I know about multipliers is that they take V1 and V2 as inputs and give k*V1*v2 as output. Can I use k=10? Then, if one of the voltages is the supply itself, I could increase the bridge signal 120 times.
Or maybe, and more simply, I could use a comparator with an even lower voltage offset, such as 0.35mV. Would I have too many problems with noise then?
The problem is that my comparator has a 3mV offset, which means that changes smaller than that do not trigger my comparator. Once 3mV is 0,025% of 12V and a Wheatstone bridge gives ∆V/V ≈ (∆R/R)/4, then the minimum resistance variation I can measure is 4*0,025%=0,1%, which is only 1/20 of the total variation. In other words, I have a 5% error measurement. What can I do to improve that number (even by a factor of 2) apart from using an amplifier? Are there comparators with smaller offsets (at erasonable prices)? A tension multiplier could do the trick?
Note: all I know about multipliers is that they take V1 and V2 as inputs and give k*V1*v2 as output. Can I use k=10? Then, if one of the voltages is the supply itself, I could increase the bridge signal 120 times.
Or maybe, and more simply, I could use a comparator with an even lower voltage offset, such as 0.35mV. Would I have too many problems with noise then?