• You are viewing the forum as a Guest, please login (you can use your Facebook, Twitter, Google or Microsoft account to login) or register using this link: Log in or Sign Up
  • You can now follow UKAPS on Instagram.

affordable Tds pen.

plantnoobdude

Member
Joined
17 Mar 2021
Messages
757
Location
uk
Hi, i'd like a tds pen preferably under 20 pounds. should i get one in microsiemens? or ppm. I have no idea about the conversion rates and stuff, what does it mean? and if you have some links to read up about it, I' greatly appreciate it! currently the best one seems to be a HM-tds-3
 

arcturus

Member
Joined
6 May 2021
Messages
444
Location
DE
Hi, i'd like a tds pen preferably under 20 pounds. should i get one in microsiemens? or ppm.
Most measure TDS (in ppm) and conductivity (EC, in micro Siemens). EC would be preferable, but, unfortunately, most people use TDS...

I have no idea about the conversion rates and stuff, what does it mean?
TDS is not a standard unit but a quantity. The different scales are a representation of the electrical conductivity (EC) in specific solutions (e.g. TDS 700 is based on KCl, TDS 500 on NaCl).

You really do not need to understand what EC and the TDS scales mean. What you need to know is which scale is your probe using. If the probe measures EC and TDS, then you can determine which TDS scale is in use (it will likely be TDS 500). After that, you just need to be careful not to be using TDS values in different scales. Different countries can use different scales and, often, the scale is not stated, so you have no idea which TDS scale was used, which can generate a large error in the reading...
and if you have some links to read up about it, I' greatly appreciate it!
<TDS scales>.
currently the best one seems to be a HM-tds-3
I have two cheap probes and a more expensive one and they all report the same values...
 

plantnoobdude

Member
Thread starter
Joined
17 Mar 2021
Messages
757
Location
uk
Most measure TDS (in ppm) and conductivity (EC, in micro Siemens). EC would be preferable, but, unfortunately, most people use TDS...


TDS is not a standard unit but a quantity. The different scales are a representation of the electrical conductivity (EC) in specific solutions (e.g. TDS 700 is based on KCl, TDS 500 on NaCl).

You really do not need to understand what EC and the TDS scales mean. What you need to know is which scale is your probe using. If the probe measures EC and TDS, then you can determine which TDS scale is in use (it will likely be TDS 500). After that, you just need to be careful not to be using TDS values in different scales. Different countries can use different scales and, often, the scale is not stated, so you have no idea which TDS scale was used, which can generate a large error in the reading...

<TDS scales>.

No idea about the accuracy of these probes. But I have two cheap probes and a more expensive one and they all report the same values...
Ugh my head is spinning, maybe ill try understand when I'm not half asleep!
No idea about the accuracy of these probes. But I have two cheap probes and a more expensive one and they all report the same values...
reassuring! thanks for the help.
 

plantnoobdude

Member
Thread starter
Joined
17 Mar 2021
Messages
757
Location
uk
so it is tds 500 (NaCl) I think Ill order it tomorrow the reviews seem pretty positive and it's quite affordable.
 

Sam66

Member
Joined
6 Jan 2022
Messages
52
Location
Cambridgeshire, UK
Have you seen this thread?
 

MichaelJ

Member
Joined
9 Feb 2021
Messages
1,690
Location
Minnesota, USA
Hi @plantnoobdude A good TDS Pen is worth investing in... I use and recommend this one. Very accurate. But you can get a cheaper one. Just make sure whatever you get has Automatic Temperature Compensation and you know the EC conversion factor which for this product is 0.5 (based on KCl which is the International calibration standard) - some are 0.64, some are 0.7. The conversion factor is good to know, in case you want to compare notes with someone who also know their conversion factor or denote their conductivity in mS/cm and you want to convert that back to "your" TDS.

Cheers,
Michael
 

jaypeecee

Member
Joined
21 Jan 2015
Messages
2,695
Location
Bracknell
currently the best one seems to be a HM-tds-3
Hi @plantnoobdude

I would advise against the above. If you look at the reviews of this meter on Amazon UK, my review may still be there. In a nutshell, the plastic membrane on the front 'panel' peeled away from the body of the meter after a few days' use. It would have readily allowed water to get inside it. Sadly, at this price, I wasn't surprised.

There has been a lot of recent discussion here on UKAPS about 'TDS' meters. Take a look around.

JPC
 

plantnoobdude

Member
Thread starter
Joined
17 Mar 2021
Messages
757
Location
uk
Hi @plantnoobdude

I would advise against the above. If you look at the reviews of this meter on Amazon UK, my review may still be there. In a nutshell, the plastic membrane on the front 'panel' peeled away from the body of the meter after a few days' use. It would have readily allowed water to get inside it. Sadly, at this price, I wasn't surprised.

There has been a lot of recent discussion here on UKAPS about 'TDS' meters. Take a look around.

JPC
huh, odd most reviews seem pretty good. I really don't want to spend much on a tds meter and i'd rather spend it on plants lol. any other budget friendly options you know of? I wouldn;t like to spend ~50 pounds on a tds meter. maybeee 30. I'm also thinking of getting a cheap one on ebay and seeing if i luck out haha.
Just make sure whatever you get has Automatic Temperature Compensation
yes it does.
 

jaypeecee

Member
Joined
21 Jan 2015
Messages
2,695
Location
Bracknell
huh, odd most reviews seem pretty good.
Hi @plantnoobdude

Perhaps the manufacturers corrected the problem and recent reviews reflect this?
I wouldn;t like to spend ~50 pounds on a tds meter. maybeee 30. I'm also thinking of getting a cheap one on ebay and seeing if i luck out haha.
It's essential that you can put your full trust in test equipment. It's false economy to do otherwise. At the very least, you will need calibration solution to check the accuracy of the meter from time to time.

JPC
 

plantnoobdude

Member
Thread starter
Joined
17 Mar 2021
Messages
757
Location
uk
I have used this meter Charterhouse Aquatics: D-D TDS Meter and Digital Thermometer which is just a rebranded amazon one. Or the TDS-4 HM Digital TDS-4 Pocket-Size TDS Meter
now those are in my price range!
It's essential that you can put your full trust in test equipment. It's false economy to do otherwise. At the very least, you will need calibration solution to check the accuracy of the meter from time to time.
i can make my own right?
 

dw1305

Expert
UKAPS Team
Joined
7 Apr 2008
Messages
13,862
Location
nr Bath
Hi all,
At the very least, you will need calibration solution to check the accuracy of the meter from time to time.
That is one of the advantages of conductivity meters, you can make your own <"conductivity standards">.
It's essential that you can put your full trust in test equipment.
I would most wholeheartedly agree with that. Personally I would want something like this <"HI-98311 EC, TDS and Temperature Tester, Low Range"> and then I would have peace of mind.
I wouldn;t like to spend ~50 pounds on a tds meter.
<"Fifty pounds should buy you"> a budget <"low range meter">, something like the <"Primo 5">, they are low maintenance bits of kit and much more robust than pH meters. It could (should) last ten years, so that is £5 a year.

cheers Darrel
 

erwin123

Member
Joined
4 Mar 2021
Messages
856
Location
Singapore
I've tested my cheap china TDS pen by measuring RO water (pen reports RO water as 0ppm), and then adding Calcium Chloride / Epsom Salts and seeing whether the reading roughly matches theoretical expected values. And it appears to be correct, within a few percentage points.

For aquarium use, if my readings of my tank water are 120ppm -140ppm but in reality they are off by even up to 10%, I think its ok, for what I am using the TDS meter for, which primarily is (i) to check there are no strange fluctuations (which could indicate root tab leakage for example or some other problem) (ii) it is generally within TDS range 'recommended' by the internet for my shrimp.
 

arcturus

Member
Joined
6 May 2021
Messages
444
Location
DE
now those are in my price range!
You can also buy two cheap ones from two actual different brands (and not the same rebranded device) and check if they read the same value ;)

i can make my own right?
Yep, you can make your own KCl calibration solution or just buy a bottle of ready made calibration fluid. Check if there a calibration screw on the device; more expensive ones are usually calibrated electronically.
 

MichaelJ

Member
Joined
9 Feb 2021
Messages
1,690
Location
Minnesota, USA
I've tested my cheap china TDS pen by measuring RO water (pen reports RO water as 0ppm), and then adding Calcium Chloride / Epsom Salts and seeing whether the reading roughly matches theoretical expected values. And it appears to be correct, within a few percentage points.

For aquarium use, if my readings of my tank water are 120ppm -140ppm but in reality they are off by even up to 10%, I think its ok, for what I am using the TDS meter for, which primarily is (i) to check there are no strange fluctuations (which could indicate root tab leakage for example or some other problem) (ii) it is generally within TDS range 'recommended' by the internet for my shrimp.
I very much agree with this pragmatic assessment of the situation. If your device is accurate within 10% then it's actually pretty good. Even if your chasing specific water for say breeding very soft-water fish its likely not going to matter if your TDS is 30 ppm, 25 ppm or 35 ppm... and if your running a hard-water tank its definitely not going to matter if your TDS is 300, 270 or 330.

Of course, not everything will register as TDS (the compounds needs to carry a charge to do so), but the best general use of a TDS pen is being able to gauge the health status and maintenance level of the tank... If you're seeing TDS creep over time it's a good indication that you're not doing enough or large enough water changes or something is leaching into the water column, your dosing too much fertilizer (or not enough if you register an unanticipated drop over time) etc. When I prep my WC water (with NPK,Ca,Mg) I always take the TDS to verify I am seeing the levels I am expecting.

I consider a reliable TDS meter just as important as a reliable thermometer.

Cheers,
Michael
 

jaypeecee

Member
Joined
21 Jan 2015
Messages
2,695
Location
Bracknell
...but the best general use of a TDS pen is being able to gauge the health status and maintenance level of the tank... If you're seeing TDS creep over time it's a good indication that you're not doing enough or large enough water changes or something is leaching into the water column, your dosing too much fertilizer (or not enough if you register an unanticipated drop over time) etc.
Hi @MichaelJ

Monitoring Conductivity/TDS is definitely a wise thing to do and it's very cost-effective. But, it does rely on electrical conductivity changes of the aquarium water. However, an increase in organic waste would likely go undetected, wouldn't it? That's why I like to monitor ORP/Redox. Right now, the tank alongside me is showing +385mV. When all is well, it lies between +350mV and +400mV. In other words, no cause for concern at the moment. When organics build up, ORP/Redox goes down. I realize that very few freshwater aquarists use an ORP/Redox electrode but that's what makes me a geek!

JPC
 

MichaelJ

Member
Joined
9 Feb 2021
Messages
1,690
Location
Minnesota, USA
Hi @jaypeecee,
Hi @MichaelJ

Monitoring Conductivity/TDS is definitely a wise thing to do and it's very cost-effective. But, it does rely on electrical conductivity changes of the aquarium water. However, an increase in organic waste would likely go undetected, wouldn't it?
It presumably depends on the waste, but TDS is definitely not the whole story - but its a good one nevertheless!

That's why I like to monitor ORP/Redox. Right now, the tank alongside me is showing +385mV. When all is well, it lies between +350mV and +400mV. In other words, no cause for concern at the moment. When organics build up, ORP/Redox goes down. I realize that very few freshwater aquarists use an ORP/Redox electrode but that's what makes me a geek!
Yes, Oxidation-reduction potential is a good measure of the tanks ability to break down waste. It might be an interesting thing for me to get an ORP meter - It will give me something new to worry about and we can geek out comparing millivolt readings :lol: Any recommendations that wont break the bank?

Cheers,
Michael
 

fredi

Member
Joined
25 Feb 2013
Messages
65
Hanna HI-98301 is available on Amazon for just over £50 delivered to uk inc taxes
Bargain imho

 
Top