View Full Version : pinpoint salinity meter for testing ro/di also?

07/14/2005, 01:40 PM
I just bought a pinpoint salinity meter. I'm starting to look into ro/di units too and was reading a little about tds meters including Randy's article about them.

I was just thinking that since the salinity meter is basically a conductivity meter and that is also what tds meters are, can I check my ro ouput with the salinity meter? I'd have to figure out how the salinity reading should best be converted to a tds reading, but I assume zero is zero. Conversion may be an issue for checking my tap water... Is this off base or what?

07/14/2005, 02:53 PM
Sorry but that meter does not test low enough for RO water. The meter values you see on it are 0-65 mS, your tank needs to read 53 mS, that = 53,000us and RO water is only a few uS. The lowest number you can get on the meter is .1 mS = 100uS = about 50 ppm TDS. An RO's need to get to 0-5 ppm TDS

07/14/2005, 02:58 PM
Ahh, makes sense to me - thanks!

Randy Holmes-Farley
07/15/2005, 06:06 AM
Pinpoint sells a different meter with that low range. They call it a conductivity meter,even though both of them are, just with different ranges.

11/03/2006, 05:15 AM
I made a post over in the filtration forums yesterday about my salinity meter fluctuating. I calibrated it with the 53.0 fluid. I am seeing the numbers jump up and down in both the fluid and the tank water.
I know the PH probes start doing this when they are out of calibration (usually need replaced) but I dont remember the salinity meter fluctuating.

Bad meter? bad probe? stray current in the tank?

Randy Holmes-Farley
11/03/2006, 11:31 AM
How much do they move? All meters take a minute or so to equilibrate because there is a temperature sensor built into it that takes a bit to come to temperature, but after that the readings should certainly not vary over time by more than 0.1 or 0.2 mS/cm.

It may be electrical interference. Try putting the water in a cup and take it away from the tank.

11/03/2006, 12:07 PM
Hey thanks Randy. It was suggested to me that the MH lights might be causing interference and another person statedthey hd fluctuations using the power adaptor in place of the battery.
Seems American Marine would be aware of this and try to produce a product that was more stable.
I am going to connect it to a power source that is isolated from the rest of the 'stuff' n the tank as well as compare the power transformer supply and battery powered supply.
* the water in a cup is a good one too!, thnks again.

11/03/2006, 12:08 PM
oh and it fluctuates very rapidly... per second readings are different.

11/03/2006, 12:16 PM
How are you runing the meter on AC or batteries ?

Randy Holmes-Farley
11/03/2006, 12:27 PM
Seems American Marine would be aware of this and try to produce a product that was more stable.

American Marine is aware of it, and points out that it is ballast and light suppliers that are in violation of FCC regulations, not their product.