Code change for Meter Hydros 21 CTD

This topic has 4 replies, 4 voices, and was last updated 2022-06-23 at 7:13 PM by Matt Barney.

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2022-06-21 at 12:10 PM #17109
Matt Barney
Participant
I don’t recall seeing any announcement on the forums, so I thought I’d share with everyone that the latest Hydros 21 sensors (Generation 2) require ModularSensors version 0.33.3 or later. We recently learned this after replacing a failed sensor in the field, and our Mayfly could no longer communicate with it. Since we have dozens of EnviroDIY stations deployed across the country, we don’t proactively install the latest version of the MS library unless there is a specific reason to do so.

Just letting others know so that they can avoid having this issue.

Matt

Trout Unlimited
2022-06-21 at 1:03 PM #17111
fisherba
Participant
Noted. Thank you. This is in my next couple weeks of existence.
2022-06-22 at 2:02 PM #17113
Stephen H
Participant
Does the new setting still work with the older sensors? Do we need to maintain 2 sets of code? Thx.
- 2022-06-22 at 9:27 PM #17114
  Shannon Hicks
  Moderator
  Yes, the update made to the ModularSensors code in in order to fix Hydros 21 is backwards compatible. I mentioned it last week in this post: https://www.envirodiy.org/topic/hydros-21-decagon-ctd-reading-error/#post-17066
  
  It seems that in the past year Meter Group made some changes to the amount of time the CTD sensors need to take a measurement, so we increased the wait time from 500 milliseconds to 1000 milliseconds. If you use the new code to talk to an older sensor, all you’re doing is waiting an extra half second, so there’s no reason to keep the old code.

2022-06-23 at 7:13 PM #17115

Participant

A couple bits of additional info. To visually identify whether your Hydros 21 is a Gen 1 or a Gen 2, see attached photos of the sensor head on each version. Note that some Gen 1’s had red cables, but not all.

Second, as Shannon noted in the post she linked to above, the address-setting on the Gen 2 is slightly more finicky; you just have to repeat it a few times. Here’s my serial output from the b_address_change.ino sketch:

Opening SDI-12 bus... Powering up sensors... Checking address 0...Vacant Vacant Vacant Checking address 1...Vacant Occupied Sensor active at address 1. Enter new address. Readdressing sensor. Success. Rescanning for verification. Checking address 0...Occupied Sensor active at address 0. Enter new address. Readdressing sensor. Success. Rescanning for verification. Checking address 0...Vacant Vacant Vacant Checking address 1...Occupied Sensor active at address 1. Enter new address.

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Opening SDI-12 bus...
Powering up sensors...
Checking address 0...Vacant
Vacant
Vacant
Checking address 1...Vacant
Occupied
Sensor active at address 1.
Enter new address.
Readdressing sensor.
Success. Rescanning for verification.
Checking address 0...Occupied
Sensor active at address 0.
Enter new address.
Readdressing sensor.
Success. Rescanning for verification.
Checking address 0...Vacant
Vacant
Vacant
Checking address 1...Occupied
Sensor active at address 1.
Enter new address.

Note the “Checking address 1…Vacant
Occupied”. Then after the first “Enter new address” prompt, I typed 1, but it came back with “address 0…Occupied”. So be persistent and your change will take.

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