I'm using two identical data logging devices that each have two sensor inputs for 4 total inputs to log temperature changes using thermistors. I currently have over 10 sensors that I need to log, but I don't really need to log them all at once. I can define several groups of up to four sensors each to log at a time. The problem is how to do this and not to kill the devices in the process.
One thing to note is that the inputs inside the devices are not implemented exactly the same. IN1 requires the use of an extra 1K resistor wired to a 5V source, while IN2 has that done internally inside the device.
I'm attaching two schematics, the first one is of the device inputs and the second one is what I was thinking of putting together originally to be able to connect multiple sensors to the four inputs. The problem I'm seeing is that if the switches are turned to the same positions (say all switches are at position #1), then all four inputs are interconnected together and I'm not sure whether the devices will be OK with it or not. In terms of data logging itself it's not an issue, since this would be an invalid configuration, I'm only worried for the safety of the devices.
What do you guys think? Maybe add a diode to each of the inputs? Not sure if this will affect the measurements though.
One thing to note is that the inputs inside the devices are not implemented exactly the same. IN1 requires the use of an extra 1K resistor wired to a 5V source, while IN2 has that done internally inside the device.
I'm attaching two schematics, the first one is of the device inputs and the second one is what I was thinking of putting together originally to be able to connect multiple sensors to the four inputs. The problem I'm seeing is that if the switches are turned to the same positions (say all switches are at position #1), then all four inputs are interconnected together and I'm not sure whether the devices will be OK with it or not. In terms of data logging itself it's not an issue, since this would be an invalid configuration, I'm only worried for the safety of the devices.
What do you guys think? Maybe add a diode to each of the inputs? Not sure if this will affect the measurements though.
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