Recommendation for a Salinity Probe to run off an Arduino?

[GuppyHJD]

I want to add a salinity probe to my arduino - what do you recommend? What are other's using?

 

[jsker]

I have used to probe from a controller to keep tabs on my salinity, I rely on a bench top salinity tester, to get the most accurate reading.

 

[geekengineer]

I use an EC probe in my saltwater storage tank but I had to figure out what it reads at 1.025 SG cause it doesn't match the formula if you try to calculate it out. I think if you use it in an active tank there might be too many other things in there that would throw off the reading. Maybe you could come up with some correlation but might not be always accurate. I would like to come up with a way to automate this using a refractometer but haven't gotten around to it yet. Maybe have a stepper motor pump put water on it then read it then someway to suck off the water or remove it.

 

[hmfaysal]

This works relatively well. https://www.dfrobot.com/product-1797.html

Always look for an EC Probe with K=10 to measure salinity in reef tank. Also the DF Robot breakout board accounts for other stray voltage stuff in the water.

 

[GK3]

This works relatively well. https://www.dfrobot.com/product-1797.html

Always look for an EC Probe with K=10 to measure salinity in reef tank. Also the DF Robot breakout board accounts for other stray voltage stuff in the water.

+1 to using this.

Yea the breakout board should isolate the probe but a return pump in the water will still cause noise in the reading.

You would want to do one of two things with this probe:

1. Forget the accuracy of the reading relative to something like refractometer and focus on the consistancy. For example your refractometer may tell you that the sg is 1.025 but your sensor on the Arduino says 1.030. Who cares. You know that 1.030 is where it should be and so you look only for deviations from 1.030 to know something is wrong.

2. measure salinity in an isolated container. Pump water in, make your measurement, pump water out. Repeat each time you want a measurement. This is the best way if you want accuracy on the measurement. It will remove all the electrical interference.

 

[geekengineer]

Agree with the K=10 for the probe. You can use a voltage isolation circuit for the probe so you don't need to do it outside the tank. I use the Atlas Scientific board though, but its more expensive. This allows you to use a I2C voltage isolator circuit. I'm not sure if the DFRobot has the equivalent. I think theirs's is an analog output so you would have to have a analog voltage isolator circuit instead.

 

[GuppyHJD]

Agree with the K=10 for the probe. You can use a voltage isolation circuit for the probe so you don't need to do it outside the tank. I use the Atlas Scientific board though, but its more expensive. This allows you to use a I2C voltage isolator circuit. I'm not sure if the DFRobot has the equivalent. I think theirs's is an analog output so you would have to have a analog voltage isolator circuit instead.

I have the Atlas Scientific EZO board and the A.S. Probe. Do you calibrate in I2C mode or calibrate in UART and then switch to I2C? My ino code sends the calibration command but the board/probe do not seem to see it.