I am trying to build a circuit to measure input resistance of a coil on a larger system the good side of the coil resistance would be between 310 ohm and 380 ohm anything below or above I would like it to reject it, any help on a circuit would be greatly appreciated.
If it is just resistance you need to measure, you can run a current through it and measure voltage, use a comparator to detect the two levels and light an LED or something.
I would do it as MrAl suggest. Run a constant current through the winding, for example 10 mA. Your acceptable resistance range is 310 to 380 ohms. So 10 mA would have a voltage drop across the coil of 3.1 to 3.8 volts. Run the voltage through a window comparator with your window of 3.1 to 3.8 volts. Anything in range is a pass and anything above or below is a fail.
I remembered something I would use. If this is for an industrial type test system there is a company called Calex that make some useful little sources and among them is **broken link removed**. The basic unit is adjustable from 0.5 to 50 mA. Here is the link to the data sheet. Saves you building your own current source. I liked powering them from 24 VDC.
Next you can just build a simple Window Comparator circuit, scroll down **broken link removed** for a window comparator circuit. I would use the LM393 since you want two comparators and that is a dual comparator. Again, you can buy a turn key solution comparator but they do get pricey.
Just depends on how much you want to put into the test system.
Thank you for your response I got me thinking and I unfortunately only have a simple simulator so I managed to get it to work with two op amps I'll build it and see how it works