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TDS pen recommendations
- Thread starter Aqua360
- Start date
dino21
Member
We have a HM Digital TDS -3 which also has temperature compensation and temp display.
Its can be calibrated by a trim pot on the rear of the pen using the 342 fluild.
You will see them one the usual sites but seems there a lot of cheap HM clones that do not have adjusters so best to buy from a reputable seller.
eg TDS-3 Handheld Meter With Carrying Case
Its can be calibrated by a trim pot on the rear of the pen using the 342 fluild.
You will see them one the usual sites but seems there a lot of cheap HM clones that do not have adjusters so best to buy from a reputable seller.
eg TDS-3 Handheld Meter With Carrying Case
Bradders
Member
You could invoke a small war by asking that question. 😆
Hi all,
There is a section in <"Some handy facts about water"> under "Electrical Conductivity" and in some of the subsequent posts in that thread.
cheers Darrel
In terms of use they are pretty much <"Plug and Play"> & <"Tank Transformation! House Move! I’m scared but join me for the ride!">
There is a section in <"Some handy facts about water"> under "Electrical Conductivity" and in some of the subsequent posts in that thread.
cheers Darrel
aquanoobie
Member
TDS meter is the easiest and can be the cheapest gadget. To check its accuracy and calibration, dissolve 0.3 grams of kitchen salt in 1 L distilled water and read 300 ppm on NaCl scale, or 614 on µS scale.
The reading tells you the amount of dissolved compounds in water but doesn't tell you what kind.
hypnogogia
Member
That depends on the conversion factor. In North America it's 2, in Europe it's likely to be 1.6 - from what I've read, anyway.
aquanoobie
Member
Excellent article, thank you!
Is there one about biological oxygen demand BOD, a measure of the amount of oxygen required to remove waste organic matter from water in the process of decomposition by aerobic bacteria?
TDS is a basic electrical resistance measurement expressed as inversed conductivity value. See Ohm and Siemens.
Dissolved 0.3 grams of kitchen salt in 1 L of distilled water makes 300 ppm NaCl solution no matter what conversion factor. On TDS testers calibrated in µS this solution displays 614 because this is the real electrical conductivity expressed in inversed value of Ohm, the Siemens unit.
hypnogogia
Member
- In the US, we use a 500 PPM scale. That means that 1 µS/cm = 0.5 PPM. Note: µS stands for micro-Siemens. This weird µ is a Greek letter, denoting ‘micro’ or 1 millionth Siemens (10-6 for math-savvy guys).
- In Europe and internationally, we use a 640 PPM scale. That means that 1 µS/cm = 0.64 PPM.
- Australia uses a 700 PPM scale. That means that 1 µS/cm = 0.7 PPM.
Source - Microsiemens To PPM Calculator: Convert µS/cm To PPM (+ 3 Charts)
Hi all,
This should cover it: <"water change routine (again)!">.
cheers Darrel
There isn't an article as such, I was going to include it in the "Cycling" article, but I haven't written it yet. I'll link in some more threads at lunchtime when I have some time.
This should cover it: <"water change routine (again)!">.
cheers Darrel
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aquanoobie
Member
The scale is not divided by country habits but by what one wants to measure. Do you want to get NaCl ppm value or real electrical conductivity value, etc.
aquanoobie
Member
This website publishes ppm as PPM and calls µ a weird letter. I have to say, not very convincing place to learn from.
hypnogogia
Member
I have to say I was a little confused by it as well. It does seem to make more sense that conversion actor changes depending on the dissolved solid and that the scale of µS/cm doesn't change. Thanks for clearing that up.
Hi all,
As you say the <"SI unit is the Siemen (S)">, and it is the reciprocal (1/Ohm) of resistance (it used to be the "Mho" ("Ohm" backwards)). They <"are all derived units">, other than conductivity (in microS / cm in dilute solutions), which is why we recommended using conductivity without <"a conversion factor">.
cheers Darrel
That is it, but conductivity, not PPM TDS. You can only measure the Total Dissolved Solids, by evaporating a known volume of water to dryness. I've done this and <"I really can't recommend it">.
As you say the <"SI unit is the Siemen (S)">, and it is the reciprocal (1/Ohm) of resistance (it used to be the "Mho" ("Ohm" backwards)). They <"are all derived units">, other than conductivity (in microS / cm in dilute solutions), which is why we recommended using conductivity without <"a conversion factor">.
This is one reason I like conductivity meters, you can make up the <"calibration solutions really easily">.
cheers Darrel
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dino21
Member
A timely thread as we have just been adding a TDS sensor to our tank which we can use for either in tank readings or for RO / DI water quality.
Making your own salt calibration fluid can be a bit hit and miss, depending on how accurate you want things, even with some of those very small scales which say from 0.1g .
You can buy HMs cal 342 fluid but quiet expensive, but a trip to your local hydro/pot shop you can buy a 300ml bottle of EC 1.413 / 706 calibration fluid for under a fiver.
For Zero reference a cheap bottle of CarPlan Deionised water from the bigger supermarkets works well.
Making your own salt calibration fluid can be a bit hit and miss, depending on how accurate you want things, even with some of those very small scales which say from 0.1g .
You can buy HMs cal 342 fluid but quiet expensive, but a trip to your local hydro/pot shop you can buy a 300ml bottle of EC 1.413 / 706 calibration fluid for under a fiver.
For Zero reference a cheap bottle of CarPlan Deionised water from the bigger supermarkets works well.
Hi all,
cheers Darrel
Use <"serial dilution">, it takes away the need to very accurately measure small weights or volumes.
The calculation is here: <"A simple continuous and fail-safe water-change system">.
cheers Darrel
I’ve got a HM Digital HMDCOM100 pen that I have been happy with so far. Allows calibration, does EC, TDS and temp. I use it to checks TDS of my tap water , RODI water and mix water for my tank.
MichaelJ
Member
There are numerous posts on the benefits and how to use a TDS meter here on UKAPS. But in short; mainly, you use it to help ensure consistency and stability in your aquatic environment. For instance, you don't want to see your tanks TDS vary much in-between water changes. If you have build-up of fertilizers/minerals, a lot of decomposing organic waste, or leaching hardscape or a varying water source you're going to see a change - typically a spike. You want to avoid that. For more subtle changes, even if you know what your TDS is otherwise made up of, such as a spike in toxic free ammonia, Chlorine, Copper or other heavy trace metals you wont usually be able to detect those with a TDS meter as they are only found in small, but still very toxic amounts.
In addition, in a planted tank keeping soft water livestock you generally want to keep the TDS as low as possible as it directly influences osmoregulation thus the wellbeing of your livestock. This is sometimes a challenge without jeopardizing your plants nutrients needs and in particular if you have to work with whatever water comes out your tap. Fortunately, most of the soft water livestock we find in the hobby are fairly adaptable unless you plan to make them breed.
The only time you really need to know or worry about your calibration reference (conversion factor) - that is the factor that the TDS meter uses internally to convert from EC to TDS - is when you refer to or compare to other sources that quote TDS. If some source say you need to keep your TDS at say 100 ppm or what have you, it can mean an EC anywhere from 140 uS/cm to 200 uS/cm, depending on what the reference is and what TDS range is quoted (typically the factor will be x0.7, x0.64 or x0.5) - x0.5 seems to be more prevalent for lower range TDS meters - I own two different meters with the measurement range between 0-1000 ppm and both use x0.5. EC (uS/cm) is unambiguous and why it's a much better value to use rather than TDS (Total Dissolved Solids) - which no TDS meter really measures anyway as it can only truely be measured by a gravimetric analysis.
Cheers,
Michael
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How would one go about avoiding that in a tap water scenario?
