I'm developing a battery monitoring circuit. There is a problem. I use a two-channel power supply for testing instead of batteries and DVM Fluke 27II for measurement. Set A0=A1=A2=0V ENA=+5V to use only the first port mux S1A S1B. Now set the supply voltage CH1=6 volts, CH2=0 volts. On the digital voltmeter we have 0.790 volts. I'm increasing the voltage onCH2. CH1=6V CH2=3V, and on digital voltmeter we have 0.774V. Continue increasing the voltage on CH2. CH1=6V CH2=6V, and on digital voltmeter we have 0.757V Why is this happening? Why the output voltage of the multiplexer decreases with increasing voltage CH2? How to fix?