Always on TDS Meter that sends alerts or ties into the Apex.

[MTWiley]

I'm not very experienced at electrical engineering, but I'd like to start on a project of modifying an inline TDS meter, the end result that I'd like to see is:

1. Using a wall wart as the power supply instead of the battery(needed to make 2 possible at a reasonable cost)

2. Always on(currently my TDS meter requires me to push the power button and then automatically turns off after a while)

3. When the TDS gets to be above a threshold for 5 minutes (say 1 for example) it will either close a relay that's tells my trips a switch on my breakout box and I can send alerts/know it's time to replace DI via my Apex/Fusion or if I have to use an RPI/Arduino to accomplish this sends the alert itself and emails me saying that it's time to replace the DI Resin.

Is this something that a person who is fairly technical(Senior Network Engineer specializing in network automation by day and plumber/electrician/avid-diyer around the house) could expect to be able to accomplish? And if so do you have any suggestions on where to get started?

 

[oceanlife83]

I am not familiar with Apex but I know that using an arduino and a tad meter to pull in the values would work then you could send the info from the arduino using web server to get alerts.

 

[cromag27]

I understand your goal, and this may not help you achieve it, but keep in mind that inline tds meters are not that accurate. A high quality handheld is much more accurate.

 

[cypho]

This should actually be very easy. There is no difference between a TDS sensor and a salinity sensor. (Not strictly true, but for our purposes the differences do not matter)

Step 1 - Cut a tds sensor cord in half. Di
Step 2 - Cut the cord of an APEX salinity probe in half. (all we need is the wire so try to find someone who will sell or give you an old/broken probe )
Step 3 - Splice the Apex connector to the tds probe.
Step 4 - Connect the probe to the apex salinity module.
Step 5 - calibrate

You can actually you skip step 5 if you want. The absolute value does not really matter. All you really need to do is watch it for a while to see what the range of "normal/good" readings are. Then program the apex to send you an alert any time the value is higher than that.

 

[MTWiley]

Fair enough, I'm assuming that I'd calibrate using the "447 mS Conductivity Solution"?

 

[cypho]

That would probably work.

But the closer the calibration fluid is to the actual values you will be measuring the better. I don't know what your calibration options are with the apex salinity module, but the best calibration would be a 2 point calibration with:

Low calibration fluid(0 tds): RODI water with new DI resin
High calibration fluid(get tds from a known good tds meter): RO water before the DI stage

 

[AZDesertRat]

Most inline TDS meters are not able to be calibrated, this is another problem with them along with not being truly temperature compensated. I think you are wasting money automating or modifying a mediocre instrument. Look for a better lab grade instrument such as a Thornton bench top conductivity meter that probably already does what you are asking.

 

[Jack20120]

Most inline TDS meters are not able to be calibrated, this is another problem with them along with not being truly temperature compensated. I think you are wasting money automating or modifying a mediocre instrument. Look for a better lab grade instrument such as a Thornton bench top conductivity meter that probably already does what you are asking.

IMO.... Most automation should be trying to look for changes in trends and not necessarily absolute values. If one wrong reading goes up by an order of magnitude, the real reading probably changed a bit, too.