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affordable Tds pen.

jaypeecee

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21 Jan 2015
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Bracknell
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:
Hi @MichaelJ

Ah, that's brilliant! Finally managed to stop myself laughing!

I have a Milwaukee MW500, which is priced at just over £100.

JPC
 

jaypeecee

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21 Jan 2015
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2,680
Location
Bracknell
I am thinking this one from Hanna HI-98120 ORP Tester ?
Hi @MichaelJ

It looks a nice piece of kit. May I suggest that you ask Hanna how well it copes with stray electric fields, which exist in the aquarium water column. This is particularly important with an ORP meter as the reading can take 15 minutes or so to stabilize. One alternative is to remove a water sample from the tank and test that.

JPC
 

MichaelJ

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9 Feb 2021
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Location
Minnesota, USA
Hi @MichaelJ

It looks a nice piece of kit. May I suggest that you ask Hanna how well it copes with stray electric fields, which exist in the aquarium water column. This is particularly important with an ORP meter as the reading can take 15 minutes or so to stabilize. One alternative is to remove a water sample from the tank and test that.

JPC
Hi @jaypeecee Well, thanks for that heads up... If none of that is a problem with the Milwaukee MW500 ? I might just get that - its 110 USD :)

Cheers,
Michael
 

plantnoobdude

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17 Mar 2021
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uk
now, let me see if i understood this correctly. my pen is callibrated from factory with NaCl (tds 500)
so if i make a solution of 500ppm Nacl then it should be 500ppm Tds? I went ahead and bought the cheap one anyway... hoping I'd luck out. I will ofcourse be testing it against a known standard
I'm guessing i should test/callibrate it against multiple solutions as well? i was thinking 100, 200, and 500. and if it's not reasonably accurate you guys can all have an, "I told you so" moment, and i'll be looking at ways to return the product!
 

MichaelJ

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9 Feb 2021
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1,690
Location
Minnesota, USA
now, let me see if i understood this correctly. my pen is callibrated from factory with NaCl (tds 500)
so if i make a solution of 500ppm Nacl then it should be 500ppm Tds? I went ahead and bought the cheap one anyway... hoping I'd luck out. I will ofcourse be testing it against a known standard
I'm guessing i should test/callibrate it against multiple solutions as well? i was thinking 100, 200, and 500. and if it's not reasonably accurate you guys can all have an, "I told you so" moment, and i'll be looking at ways to return the product!

Mine is fairly bang on in a pure NaCl solution. Take 1000 ml of Distilled water add 100 mg of NaCl (and dissolve) in increments of 100 mg up to say 500 mg. (of course you need a good precision scale to do that)... depending on the conversion factor you should ideally measure 100, 200, 300, 400, 500 ppm... My HI-98301 is within 2-3% of these numbers.

Cheers,
Michael

 
Last edited:

plantnoobdude

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17 Mar 2021
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Mine is fairly bang on in a pure NaCl solution. Take 1000 ml of Distilled water add 100 mg of NaCl (and dissolve) in increments of 100 mg up to say 500 mg. (of course you need a good precision scale to do that)... depending on the conversion factor you should ideally measure 100, 200, 300, 400, 500 ppm... My HI-98301 is within 2-3% of these numbers.

Cheers,
Michael
alright perfect! my scale is pretty good but not perfect. ill measre probably around ~5 g of salt and dillute it from there
 

plantnoobdude

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17 Mar 2021
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hm tds-3 has arrived and it is quite accurate. it is within range of around 5ppm when using 100ppm solution, and around 10ppm when using 200ppm. it is always within 5% of callibration fluid. I think that amount can be my error and the tds pen is reasonably accurate. lets hope it lasts longer than it did for jaypeecee! apparently it has a three year warranty though.
 
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