Welcome to EnviroDIY, a community for do-it-yourself environmental science and monitoring. EnviroDIY is part of WikiWatershed, an initiative of Stroud Water Research Center designed to help people advance knowledge and stewardship of fresh water.
New to EnviroDIY? Start here

Reply To: HYDROS 21 no longer vented… any idea when this changed?

Home Forums Environmental Sensors HYDROS 21 no longer vented… any idea when this changed? Reply To: HYDROS 21 no longer vented… any idea when this changed?

#15523
Shannon Hicks
Moderator

    Are you using a sensor with bare wires at the end, or with the molded stereo plug?  Is it a red cable or a black cable?  We’ve bought hundreds of CTD-10 and now the Hydros 21 sensors (only the name changed when the company changed from Decagon to Meter, and there was no design change).  We bought a bunch earlier this year, and every one we’ve ever used has a small Gore-Tex sleeve about a foot from the end of the cable that provides the vent used for the pressure sensor atmospheric reference.  Even their new Generation 2 Hydros 21 sensor (due to be released soon) that we’ve been testing recently has the vent.  If your sensor doesn’t have a vent somewhere along the cable, then either it’s an error and it’s missing, or you’re using a bare-wire terminated cable and the end of the cable allows the air into the jacket to provide the reference (the newer cables have a dedicated air tube inside the cable whereas the old cables relied on the airspace between the wires).   Either way, I recommend contacting Meter Group tech support, they’ve always provided great customer support for us over the past 7 or 8 years that we’ve been using their sensors.  Did you try putting the sensor in a bucket of water at a constant depth and then logging depth over a few days to see if you see atmospheric pressure affecting the data?