Hello,

I'm just wanting to check that I haven't got hold of the wrong end of the stick here.

We're looking at monitoring some Decagon 10HS sensors with a DT80 or DT82E. This is a 3 wire sensor with the following attributes:
Measurement Time 10 ms
Power requirements 3 VDC @ 12 mA to 15 VDC @ 15 mA
Output 300 - 1250 mV, independent of excitation voltage

I'm thinking I could connect the excitation lines to the 5V switched out, and then hook up 3 sensors to one analog input in a shared-terminal configuration. It would mean that all three sensors would be powered for the reading of each, but given that they'll be read as near to simultaneously as possible, I don't foresee that being a problem.
We'll almost certainly be using a 12V external battery for power.

Are there any potential problems with this setup? Or have I misunderstood how this should work in some way?

Thanks,
Bruce.

Good morning b.alcorn,

The 5 Volt switched power supply can deliver up to 25 mA.
Powering 3 sensors each drawing at least 12 mA is a total of 36 mA or more so that won't work.

You will need to look at a separate external power supply to power these sensors.

Cheers,
Roger

Hello Roger,

Thanks, that's a wrinkle I hadn't considered.

Is there any reason I couldn't use the 12V switched out, to wire it up as in the attached image?

Failing that, I'll just run the probe power line through the relay, then to the battery.

Thanks,
Bruce

Good afternoon Bruce,

That should work.
Technically you are breaking the channel isolation (connecting the digital ground to the analog #) but because they all use the same power supply you shouldn't have common mode issues.

Cheers,
Roger