Design of Window Comparator Circuit w/ Mutually Exclusive LED Indicators
You need to make four window comparitors. Fortunately this is easy with the LM339 as it has open-collector outputs which can be joined together to form a wired AND function.



Figure 1. The internals of an LM339 comparitor. Note the open-collector output.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 2. By wiring the outputs together as shown the LED will turn on when the voltage is inside the window set by VR1 and VR2.

How it works:


If both comparitor outputs are high their output transistors are off and the collector is floating. R1 will pass current to LED D1.
If the input voltage goes above the upper window voltage set by VR1 then CMP1 will turn off and short out LED D1.
If the input voltage goes below the lower window voltage set by VR2 then CMP2 will turn off and short out LED D1.


You need four of these circuits. I recommend 10-turn pots rather than a precision resistor divider chain. Add one more pot for calibration and it should be a simple job to set everything up.

Don't skip the decoupling capacitors on each chip.