# My new TDS pen



## siddaa1 (10 Nov 2013)

Trans Instruments Senz µSiemen Meter for Hydroponics, Hydroculture, Aquaculture  | Eco City Hydroponics Singapore Online Store


Got it off ebay never used and for an absolute steal.

Slight problem..........the readings are in mili Siemen and I haven't got a clue what my TDS is hahaha, not only that but I think I'll need to purchase some 12.88ms calibration solution.

My reading out of the box is 0.1 which can't be right as it states that I would have ultra pure water which clearly straight outta the tap and in my new tank for 2 hours wouldn't be the case.

Any TDS or mili siemans boffins able to enlighten me on this please :/


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## OllieNZ (10 Nov 2013)

1 milli seimen = 1000 micro seimens.
1.56 micro seimens = 1ppm tds


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## Andy D (10 Nov 2013)

It seems that to convert micro-Siemens to ppm you multiply by 700. So your reading of 0.1 would be 70ppm indicating quite soft water.

(But not ultra-perfect  )


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## Nathaniel Whiteside (10 Nov 2013)

Woulda preferred a normal TDS pen myself..


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## siddaa1 (10 Nov 2013)

Makes sense Andy. Aren't I lucky having nice soft water 

Nathaniel, yeah I thought that when it arrived but I presume it's very accurate and will last a long time.

Sorry Ollie just noticed your post there, using that formula my water today is now 192 TDS, I would imagine that a rise from 64 yesterday to 192 today would be about right? The waters fresh in as of yesterday and the first time the tank has been filled, there's debris floating etc.


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## Yo-han (10 Nov 2013)

Converting conductivity to TDS is basically impossible. It really depends on the type of dissolved solids to no how much electricity they conduct. Sodium chloride has another conversion (470-500) than potassium chloride (500-570) and a totally different conductivity than a large organic molecule. In practice the conversion of Andy D is probably closest, but you really can't put a real number in ppm. The problem with 'real' TDS meters is that they do the same as an EC meter. They measure conductivity and use a standard number to convert to TDS. Depending on the device this number is usually the one for sodium chloride and for our aquaria thus way off! Best to use an EC meter IMO


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## DTL (10 Nov 2013)

Some interesting info on the subject here :
 Conductivity convertor, Siemens into TDS PPM and MHO
 TDS and Electrical Conductivity -  Lenntech


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## siddaa1 (10 Nov 2013)

Top drawer DTL


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## Andy D (10 Nov 2013)

Yo-han said:


> Converting conductivity to TDS is basically impossible. It really depends on the type of dissolved solids to no how much electricity they conduct. Sodium chloride has another conversion (470-500) than potassium chloride (500-570) and a totally different conductivity than a large organic molecule. In practice the conversion of Andy D is probably closest, but you really can't put a real number in ppm. The problem with 'real' TDS meters is that they do the same as an EC meter. They measure conductivity and use a standard number to convert to TDS. Depending on the device this number is usually the one for sodium chloride and for our aquaria thus way off! Best to use an EC meter IMO



Makes sense as I did read there was a conversion range. Typically you could multiply the figure by any number between 640 and 700 to be in the right area. 700 seems easiest to remember if nothing else.


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## Yo-han (10 Nov 2013)

DTL said:


> Some interesting info on the subject here :
> Conductivity convertor, Siemens into TDS PPM and MHO
> TDS and Electrical Conductivity -  Lenntech



This calculator uses 640 as a conversion factor. Acceptable I guess, but than again, we don't even know all the dissolved organics that are in our tanks so hard to tell. If 640-700 is a good conversion factor. This means a standard TDS meter is up to 40% off!


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## siddaa1 (10 Nov 2013)

I'm gonna use it to regulate the increase, as long as the inhabitants are happy and my numbers stay within a relative parameter I'll be happy


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