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ADS1115: Using to monitor isolated devices on A0 to A1 and A2 to A3

Part Number: ADS1115

I am working on a solar system monitoring project in which the pwm charge controller has isolated input, battery and load. I put input on A0-A1 and the load on A2-A3... how does the hardware keep the 2 sources separated/ isolated because it looks like the PGA can only read one pair at a time? For the testing I have done it seems like the mux reverts from differential to single ended, shorts when switching or something where the chip gets damaged.

Is there some trick in Software that keeps one mux pair open when the other is being read or something else?  And or goes to both open then close one as needed?

Or should I be using 2 different ads1115 to read 2 power sources that must be kept isolated?  I am also having an issue with my 3rd ads1115... I have 3 running to Arduino uno r3. 0x4a gives me problems in programming and always returning -1.

None of the documents i can find give me a reference for the Arduino as to a list of programming commands and the command arguments for this chip... I believe it is an Adafruit library but of no help.. any ideas?

  • Jack,


    The ADS1115 does only read only one input at a time. The multiplexer should completely isolate the different channels. The mux is break-before-make to ensure that the input signals are never momentarily connected. If the device is being damaged, I would imagine that there is some sort of over-voltage event that might be happening. Some series resistance with the inputs may help with that.

    If you are making measurements with the device of different power supplies, the different supplies should not be isolated, and should have a common ground. Also, the inputs should not go beyond GND and VDD. If you have a unipolar supply of 0V to 5V, then you may damage the inputs if the voltage goes beyond these limits (or we say -0.3V to +5.3V for the absolute maximum ratings for these voltages).

    Are you able to send a basic schematic? It may help to see what it is that you're measuring.


    Joseph Wu

  • Jack,

    I haven't heard from you for a while so I thought I'd check on your problem with the ADS1115. As I'd mentioned in the previous post, the multiplexer should isolate the channels so that there shouldn't be any connection between the two, even momentarily. Also, if there is damage, there might be issues with the inputs going beyond the supplies, and series resistance may be helpful in protecting the device.

    I'll close this post for now. If you continue to have problems, post back here and we can continue to work on this issue.

    Joseph Wu