How accurate does a TDS meter need to be?

[sen5241b]

 

Take "GroTheory "brand TDS meter out of box. I bought it off Amazon. It was highly rated.  Put it in the solution HM Digital 1000ppm TDS Calibration Solution  It reads 1300. Retested after rinsing and drying probes but same result.

 

 

Reset it? Replace batteries? Heard you need to stir probe in solution.

The seller contacted the factory in  China I'm my behalf:

 

"Hi Scott, Thank you for your reply. The factory replied that if the TRS Meter displays about 1000, it is relatively standard, but if the TRS Meter is bought and placed for more than 1-2 days, there will be an error in the value. If you meet any thing, you can contact us at any time. Best regard! "

 

I think something got lost in translation. 

 

 

 

[howaboutme]

Unless your water is filthy at up to near 1000ppm, you should calibrate closer to what your source is. Typical that's using 342ppm solution. That said, did you put your meter in 1000ppm and it read 1300ppm? If so, just hit the calibration button and you should be set.

Edited October 11, 2021 by howaboutme

[DaJMasta]

What are you using it for?  For me, basically only checking go/no-go on RODI, it really doesn't need to be accurate at all (and as said your calibration point for that usage should be MUCH lower).  I'm sure there are applications that demand fairly good accuracy, perhaps remineralizing RODI or something, but I don't do any of that for saltwater stuff, and actual seawater has so much conductivity/TDS that 1000ppm wouldn't even be close to the full scale range you'd need (1.026 SG is about 35ppt, which would be 35,000ppm).

If you want a rated accuracy, that should be in the manual or datasheet for your unit, as they can differ between designs.  Usually these values are only valid when within whatever calibration cycle is specified, and since cheap TDS meters are so prominent, the specification could just be "nominal" values for the average unit and not actually tested by the manufacturer.

Edited October 12, 2021 by DaJMasta