Is there a digital TDS meter you would recommend?

[bekateen]

Hi All,
I'm in the market for a digital TDS meter (either just TDS, or a combo meter, or meters that measure specific GH/KH (if they exist)) and possibly a digital pH meter. Is there a brand AND model you recommend? I know that Hanna and HM Digital make several different models. Which of their models are good? What about other brands? I searched the forum for past threads about meters and found a few threads, but I didn't see specific models.
Thanks all,
Eric

[PseudaSmart]

I know that many feel that Milwaukee makes 'inexpensive' test equipment but I have found them adequate. My conductivity meter (similar to a TDS meter but not the same) does not drift as long as I keep the probe clean. I recalibrate 2x a year and it is within 1%.

There are many posts on using TDS meters and such in aquariums but I at least wanted to remind everyone that the meters measure everything in the water not just hardness. Salt, fish waste, copper, etc. will have a huge impact on the reading. I always check the water when I buy fish before putting them into quarantine. It is easy to see who salts their tanks.

My experience with Ph meters is mixed. I have one tank that a monitor all the time with no issues. It is when I start sampling water that causes trouble for me. I find I have to recalibrate frequently and after about a month it takes a longer time for the meter to settle. Perhaps it is the soft water that depletes the electrolyte in the probe so I find titration faster.

I actively use the meter for making new water and as reference when checking aquariums.

Hopefully the extra info also helps with other questions.
Jim

[Shane]

I am using this one. Tests temp, pH, TDS, and conductivity. It has a few poor reviews on Amazon, but has worked great for me for the last 3 years.
-Shane

http://www.amazon.com/Hanna-Instruments ... vity+meter

[krazyGeoff]

I use the same one as Shane, and find that it out performs a couple of other brands that I tried.
Easy to calibrate etc.
another thing that it pays to remember is that once you have a few "periods" of readings, then as long as the meter is consistent, it is the relativity between readings that is important.
For example if the TDS has been between 90 and 99 (random numbers) and then suddenly it is 150 then there is an issue.

Cheers

[Viktor Jarikov]

Home TDS meters are notoriously ill fitted. They are ok for crude measurements and even at that old fashion ones with an analog display are said by water professionals to be superior to the newer-technology digital ones. The latter may be ok for showing a difference in 100's of ppm.

That's a recommended one, made by Myron http://www.cannonwater.net/MyronL_512T10_DS_Meter.aspx Note $200 not $30-$50 for cheapies like that http://www.cannonwater.net/AquaPro_AP-1_TDS_Meter.aspx - with these you get what you paid for.

The Myron one is the one my RO installers use in the field and recommend to me (we produce ~10,000 gal a day 365 days a year).

[TwoTankAmin]

For a quick hand held spot use one I have this: http://www.tdsmeter.com/products/tds3.html

For continuous monitoring I use this: https://www.bluelab.com/products/type/m ... nitor.aspx

[dw1305]

Hi all,

Home TDS meters are notoriously ill fitted. They are ok for crude measurements and even at that old fashion ones with an analog display are said by water professionals to be superior to the newer-technology digital ones. The latter may be ok for showing a difference in 100's of ppm......The Myron one is the one my RO installers use in the field and recommend to me (we produce ~10,000 gal a day 365 days a year).

I'm not questioning the quality of the Myron meter, I like analog meters, but unless you are dealing with ultra-pure water (less then 1 microS) the rest isn't right.

TDS is slightly misleading in this case, because none of the meters measure TDS, they all measure electrical conductivity (microS) and use a conversion factor between 0.5 (for NaCl) to 0.64 (mainly (metal &) carbonate ions) to estimate ppm TDS.

Relatively cheap low range conductivity meters will give you accurate and repeatable measurements. The reason for this is that there is a linear relationship between dissolved salts and electrical conductance, although this is temperature dependent to some degree. Conductivity isn't like measuring pH or specific ions with Ion Selective Electrodes, it is a much more straight forward measurement.

All conductivity meters basically have 4 electrodes (ideally platinum coated), 2 outer and 2 inner, and an AC current is applied to the outer pair of the electrodes and then the amount of current (potential) between the inner pair is measured. Pure H2O is an electrical insulator and sea water has a conductivity of about 54,000 microS.

Any meter that offers low range (0 - 999microS) and automatic temperature compensation will give you a reasonably accurate (within a ~1 microS) result.

You can also easily make up your own calibration solutions from KCl (0.01 M KCl = 1411 μS at 25°C). Although I very rarely need to re-calibrate the lab. conductivity meters.

cheers Darrel

[bekateen]

This is all very informative. Thank you all for the suggestions and info.

... I like analog meters... Relatively cheap low range conductivity meters will give you accurate and repeatable measurements... Any meter that offers low range (0 - 999microS) and automatic temperature compensation will give you a reasonably accurate (within a ~1 microS) result... Although I very rarely need to re-calibrate the lab. conductivity meters.

Darrel, which meter(s) do you use/like?

Also what about durability? I've read several horror stories of devices breaking after just a few months or a year. I would expect more from a good device.

Cheers, Eric

[dw1305]

Hi all,
I usually get Hanna ones, but we've got a variety of makes. The ones we give the students for field work etc are digital "Hanna HI 98360", I think these were about £500 when we bought them, and they have proved pretty durable.

Before that we had "Jenway 4200", and we've still got some of these that work that are probably 15 years old.

I'm not as keen on the combined pH/Conductivity meters, but we've recently bought a few "HI 991300" combined meters (~£400), but we haven't had them long enough to pass any comment on their reliability.

The reason I don't like combined meters is that pH meters are quite high maintenance and I would estimate that we get through 2 or 3 pH meters for every conductivity meter we buy.

Durability is one reason I like analogue meters, you don't have problems with the LCD displays etc. but they aren't very portable and need to be sited permanently in a lab.

We don't have separate stock of "lab. only" or "field-work" meters now, so all the ones we buy are much more rugged than they would need to be just for use in the lab.

I think even a £50 low range meter will be accurate to 1 - 2%.

cheers Darrel

[Viktor Jarikov]

Relatively cheap low range conductivity meters will give you accurate and repeatable measurements... Any meter that offers low range (0 - 999microS) and automatic temperature compensation will give you a reasonably accurate (within a ~1 microS) result... I think even a £50 low range meter will be accurate to 1 - 2%...

Any? Great! Good to know Darrel. I got a cheaper one for $50. Will test it eventually. I don't need a ~0.5 ppm accuracy. But I need a better range than you cite (or two meters) as my water ranges from ~1400 ppm (~3500 microS) for raw well water to ~20 ppm for the raw RO water.

[dw1305]

Hi all,

But I need a better range than you cite (or two meters) as my water ranges from ~1400 ppm (~3500 microS) for raw well water to ~20 ppm for the raw RO water.

Some low range meters will do to 3999 microS. There is a ~$150 Hanna one "HI98129 - pH/Conductivity".

cheers Darrel

[bekateen]

I am using this one. Tests temp, pH, TDS, and conductivity. It has a few poor reviews on Amazon, but has worked great for me for the last 3 years.http://www.amazon.com/Hanna-Instruments ... vity+meter

I'm not as keen on the combined pH/Conductivity meters, but we've recently bought a few "HI 991300" combined meters (~£400), but we haven't had them long enough to pass any comment on their reliability.

Hi All,
Okay, so I'm deciding between the Hanna HI 99301 (appears to be similar in design to Darrel's 991300, but much cheaper) and the Hanna Instruments HI 98129. Price is basically the same for both, where I'm buying. Any opinions between the two of these?
Thanks, Eric

[dw1305]

Hi all,
The first one (HI 99301) is a "high range" meter which measures up to 20 milliS. The HI98129 ranges up to to 3999microsS (4 milliS) so it would have better resolution at lower conductivities.

It should be fine.

cheers Darrel

[bekateen]

Okay, then. And that should be fine based on what I see in my city's annual water quality report: In my town, some folks get ground water and some folks get surface water; for ground water, the TDS range is 210-580 mg/L and for surface water it's 36-230 mg/L; the respective conductivity measures are 301-840 μS/cm and 45-443 μS/cm. I'm not sure which I get; for that matter, I'm not sure that the two sources are kept separate (but I suspect they are). No matter though, because all of these readings are well within the range of the HI98129. So that's what I'll get!

Thanks all. Cheers,
Eric

P.S. I bought the HI98129. For those of you interested in the details of the product, here is its product page at the manufacturer's website: http://shop.hannainst.com/hi98129-ph-ec-tds-tester.html