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cr4hmb
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Converting Micromhos/cm to PPM

01/06/2009 4:20 AM

I would like to know how to convert micromhos/cm into PPM? And how would the increase/decrease of the temperature affect?

The reason behind this question is that an old switch is installed to alarm for high water conductivity on a tempered water system. At the same time, we are getting water sample to measure the conductivity in PPM.
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PWSlack
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#1

Re: Converting Micromhos/cm to PPM

01/06/2009 9:02 AM

<I would like to know how to convert micromhos/cm into PPM>

Roughly, 1.5μS/cm ≈ 1PPM for small concentrations of ions at room temperature and sea-level pressure, as a rule-of thumb.

<And how would the increase/decrease of the temperature affect?>

Increase in temperature causes increase in conductivity, though it is not linear - strange things happen around 0degC and 100degC at sea-level pressure, for example, as one might imagine.

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flynnstar
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#3
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Re: Converting Micromhos/cm to PPM

01/07/2009 10:04 AM

PWSlack- My thumb is a little fatter than yours, around 2-2.5 μS/cm. The conductivity of a solution of NaCl at one mg/l as equivalent basis CaCO3 is 2.53 at 25 deg C. This would be 0.85 mg/l as such. The rule applies to neutral pH solution. One mg/l, or ppm of NaOH has a conductivity of about 5 μS/cm. A ppm of HCl, about 7 μS/cm. Conversion of conductivity to ppm is always an approximation since conductivity will vary with the water composition, pH, CO2 content, and temperature of the stream.
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PWSlack
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#4
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Re: Converting Micromhos/cm to PPM

01/26/2009 6:29 AM

Quite.

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cr4hmb
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#2

Re: Converting Micromhos/cm to PPM

01/06/2009 11:17 PM

Thanks PWSlack

As i know, conductivity is the result of ionizable solids in solution; high conductivity can increase the corrosive characteristics of a water. What is the acceptable range of TDS for tempered water?

In my application, the system is equiped with Conductivity Switches that will alarm when reach as high as 800 micromhos/cm.
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PWSlack
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#5
In reply to #2

Re: Converting Micromhos/cm to PPM

01/26/2009 6:30 AM

From the description it sounds as though 800μS/cm is the upper limit of acceptability for the application.

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