EC / ppm meters.

[gonewild]

Anyone have experience or opinion for Bluelab meters?
I'm looking for a more accurate option to cheap pens.

 

[Ray]

TDS meters are EC meters to which a "conversion factor" is applied. No matter how accurate the EC meter is, applying the correct factor is critical to getting a decent TDS estimate, and each solution requires its own conversion.

Most conversion factors are based upon NaCl solutions, which don't resemble fertilizer solutions at all.

I purchased an HM Digital EC meter for about $50. It is quite accurate on the EC and has two, built-in conversions for TDS. One is reasonably close in K-Lite solutions, the other not.

The best thing to do is get a reliable EC meter and build your own standardization chart using your water and fertilizer.

For example, the true TDS of a 100 ppm N MSU WW solution is 530 ppm (0.53g/L), which is a 2g/gal solution, contributing a conductivity of 680 µS/cm. Measure the EC of the water we'll use zero in this example) and add 2g of the fertilizer to a gallon. If your meter is not reading 680 µS/cm, just determine the "true" to "read" ratio and you can apply that to any MSU WW solution - if it was 340, then you have a 50 ppm N solution.

 

[gonewild]

TDS meters are EC meters to which a "conversion factor" is applied. No matter how accurate the EC meter is, applying the correct factor is critical to getting a decent TDS estimate, and each solution requires its own conversion.

Most conversion factors are based upon NaCl solutions, which don't resemble fertilizer solutions at all.

I purchased an HM Digital EC meter for about $50. It is quite accurate on the EC and has two, built-in conversions for TDS. One is reasonably close in K-Lite solutions, the other not.

The best thing to do is get a reliable EC meter and build your own standardization chart using your water and fertilizer.

For example, the true TDS of a 100 ppm N MSU WW solution is 530 ppm (0.53g/L), which is a 2g/gal solution, contributing a conductivity of 680 µS/cm. Measure the EC of the water we'll use zero in this example) and add 2g of the fertilizer to a gallon. If your meter is not reading 680 µS/cm, just determine the "true" to "read" ratio and you can apply that to any MSU WW solution - if it was 340, then you have a 50 ppm N solution.

Thanks for the detailed information.

 

[gonewild]

I decided to buy an Apera meter. EC/pH combo.
It seems to be a well made and accurate instrument.