PM2 and Salinity Probe Reading question

[PotRoast]

My TDS meter on my RODI system is acting funny (showing TDS readings of 75 on the RO and 67 on the RODI) so I am trying to test the conductivity of RO water (NOT RODI water). I am assuming my RODI TDS meter is going bad.

I have a PM2 and a Salinity/Cond probe so I set the apex for the LOW range, set temp compensation to ZERO, and placed the probe in a test sample of RO water.

The conductivity reading is around 0083 (it was still going down some when I checked before going back to work)

How do I interpret these results? What does that reading mean exactly?

I am trying to determine if I have a faulty RO membrane...keep that in mind.

Thanks!

[apjohnson]

Borrow someone else's TDS meter and figure out the TDS situation first. Then the rest should make more sense. Bill should have one you can borrow.

--AJ

[schwaggs]

Using an uncalibrated conductivity probe won't tell you much. I would either calibrate with the proper solution for the range you are measuring (in the manual) or find another TDS probe you can use.

[jmchzn123]

Using an uncalibrated conductivity probe won't tell you much. I would either calibrate with the proper solution for the range you are measuring (in the manual) or find another TDS probe you can use.
Realize this is an old thread but if you read this maybe you can help? Is temp correction necessary? I calibrated probe as per manual but didn't do temp correction at first. I moved probe away from other probes and away from rtn pumps. Got 35ppt salinity reading. Used 53000 solution at 25c so all was good. Then I get the temp probe hook it into PM2 and decide to recalibrate. I get Carl on the phone from Neptune and we do it together. Set temp correction to 2.1 per Carl. Then find out my salinity in the tank is near 37ppt!!! I get my trusty DD ATC ocean water refractometer and it's a little under 35ppt! The amount of temp correction? What should I do. Recalibrate and forget temp correction? The tank temp really doesn't fluctuate more than 1 degree. In fact less according to the apex graphs?

[schwaggs]

When you calibrated with the temp probe enabled, did you ensure the calibration solution, salinity probe and temp probe were all at tank temp? The way I do this is is to float he calibtration solution in the tank for 30 minutes before performing the calibration.

[jmchzn123]

Calibration fluid was soaking in my sump. But there is a 1-3F difference. I have 1 packet of calibration left I'll use a digital thermometer for accuracy and try again. After 10 yrs I feel like noob salinity is the easy stuff!