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Hydros-21 Depth Temp Compensation

Home Forums Environmental Sensors Hydros-21 Depth Temp Compensation

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    • #14919
      dan@wachusett
      Participant

      My Hydros21 CTD-10 sensor depth output is highly affected by the diurnal stream temp fluctuations by upwards of 15 mm sometimes. This issue was noted in forum post # 13557:

      I recently got a quote for the CTD-10 (10m or 30′ – they only do the 10m now) with a fixed accuracy at 20C of 0.05% Full Scale or +-/5mm and no statement of how it varies with temperature (called temperature compensation).
      UpdateJan9th: I got a reply from leo.rivera@metergroup.com “We typically evaluate this from 0 to 50C and we see somewhere around +/- 2 cm in that range. It does vary sensor-to-sensor and some sensors have lower sensitivity.”
      So practically they are saying temperature compensation is challenging, and they could have the readings varied by ±25mm or 0.25% of scale – and they wouldn’t take the instrument back.
      https://www.metergroup.com/environment/products/hydros-21-water-level-monitoring/ Quote $491 per sensor and with a 10-meter cable.

      I started a new thread since the original topic of that post was about something else. Has anyone else experienced this with their Hydros21 CTD-10? We used to have the CTD-5 which did not have this problem. This unit was damaged during cleaning and replaced under warranty with a CTD-10. The replacement unit showed this problem and we returned it thinking that it was defective – Meter acknowledged that this was a “known” issue. The second replacement sensor is experiencing the same issue (illustrated in the attached plot). If anyone has any insight into this or a method to fix the problem I would be interested in hearing about it. From the quoted thread above it seems like this output is normal and expected.

      Thanks,

      Dan

    • #15324
      Scott Ensign
      Participant

      Hi Dan,

      We recently did some internal testing of this issue and will post results soon. We don’t have a “fix”, but we did measure this behavior to guide our own interpretation of data.

      Scott

    • #15378
      dan@wachusett
      Participant

      Hi Scott, I look forward to seeing your test results. Meter Group exchanged my Gen 1 Hydros21 with a brand new Gen2. I am programming it right now and will post new results after I test it. We are gearing up to expand our Mayfly network and I want to make sure we are using a dependable sensor before we purchase several units.

      Dan

    • #15383
      Matt Barney
      Participant

      Hi Dan,

      I’m curious whether it’s possible to identify Gen 1 vs Gen 2 Hydros21; are they labeled? I’m wondering what I’ve got.

      Thanks,

      Matt

    • #15476
      dan@wachusett
      Participant

      Matt,

      Sorry for the delayed response. You probably have the Gen 1 Hydros 21 sensor since the Gen 2 is brand new and I think I may have been the first one to get it. In fact, I can’t even use it yet because the ModularSensors library needs to be updated to handle some of the updates to the communications protocols. My Gen 2 has a black cable and the sensor sidewalls do not have holes like the Gen 1 has.

      -Dan

    • #15477
      James_NZ
      Participant

      Hi @dan-wachusett. I am about to order 10 x Hydros 21 units from METER Group. I have been told that they will be Gen 1, but Gen 2 will be released in a few weeks’ time. I’m trying to get some details from METER Group about the upgrade and whether it would be worthwhile waiting for a couple of weeks to get the Gen 2.

      I also see that the Gen 2 is not working with modular sensors yet. Any idea how long it will be before it can be used?

      James

    • #15478
      Shannon Hicks
      Participant

      We recently received a Gen 2 Hyrdos 21 CTD sensor from Meter Group and have confirmed that it works just fine with the Mayfly Data Logger, and using our Modular Sensors library, with just a very small adjustment made to the library.  We’re in the process of updating that now, so you should be good to order them and use them when they arrive.

    • #15479
      James_NZ
      Participant

      Thanks @shicks, great to know. Would you recommend that I push back on them for Gen-2 sensors, even if they take a bit longer to get here? It seems silly to rush things through and end up with an inferior sensor.

      James

    • #15480
      Shannon Hicks
      Participant

      We just got the sensor and haven’t done any comparison tests alongside the Gen 1 sensor to see if there’s a difference, so I can’t comment yet on anything data-wise, we just know that there’s not a communication issue with the Mayfly now that we’ve adjusted the timing of the commands in our library.

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