? about hand held TDS meters

[JCR's Reef]

I was wondering which ones where the most accurate and which place is the cheapest to buy from. I already have an inline DM1 which I need to buy solution to calibrate because I dont think its right,but I would like a seperate hand held one as well.
Also do they make a TDS meter for Saltwater to measure the Dissoved Solids in your tank? I know there is regular test kits for everything, but its hard to know when your kit its accurate. Never heard anything about this but thought I would ask.

 

[Randy Holmes-Farley]

FWIW, high accuracy is not important for RO/DI monitoring, and you can check any meter you want in commercial TDS calibration fluids. I discuss such issues in these articles:

What is TDS?
http://www.reefkeeping.com/issues/2004-04/rhf/feature/index.php

Reverse Osmosis/Deionization Systems to Purify Tap Water for Reef Aquaria
http://reefkeeping.com/issues/2005-05/rhf/index.htm


Many brands of conductivity meter are suitable for tank salinity measurement. That's how I measure salinity. Typically they need to read to at least 60 mS/cm or 60,000 ppm TDS.

American Marine/Pinpoint sells one. I discuss that method in these articles:

Using Conductivity to Measure Salinity
http://www.aquariumfish.com/aquariumfish/detail.aspx?aid=1804

Reef Aquarium Salinity: Homemade Calibration Standards
http://reefkeeping.com/issues/2004-06/rhf/index.htm


The “How To” Guide to Reef Aquarium Chemistry for Beginners, Part 1: The Salt Water Itself
http://reefkeeping.com/issues/2007-03/rhf/index.php

 

[JCR's Reef]

Thanks Randy. Finding that earlier wouldve saved me from asking that question.

 

[Randy Holmes-Farley]

:lol:

No problem.

Happy Reefing.

 

[jthomps123]

I purchased mine for something like $18 after shipping on ebay. It also had a temp meter. Seems to work fine.

 

[reef_doug]

I have the hand held Hanna TDS-1. Works fine and is under $20. I prefer the handheld vs. inline.

 

[AZDesertRat]

The HM Digital COM-100 is by far the best handheld TDS meter. I would have to disagree with Randy on accuracy personally, if I'm going to spend the time doing something I want to ensure I am doing it right. Why make 200 gallons of mediocre RO/DI water? I feel low end accuracy is critical for DI water. The other issue with accuracy is repeatability, better meters will be more consistent too. Another plus to better meters is built in tempertaure compensation and a temperature function so you are getting temp as well as TDS at the same time. I wouldn't do without mine!

 

[Randy Holmes-Farley]

I would have to disagree with Randy on accuracy personally, if I'm going to spend the time doing something I want to ensure I am doing it right. Why make 200 gallons of mediocre RO/DI water?

I don't see how that could happen if you follow my use recommendations. Suppose the meter is off by an almost incredible 50%. My recommendation is to swap out the DI as soon as you detect any rise in TDS to 1 ppm. I suppose that might now be 2 ppm if it is off in that direction. You consider that a substantial concern?

Since all that calibration does is change the slope of the response, it will still read 0 ppm TDS in 0 ppm TDS water, a fact which is easily checked in air.

Nevertheless, if that does concern you, then checking the calibration is pretty easy.