Reply To: Code change for Meter Hydros 21 CTD

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.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

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.

-Matt