[steven ainger]

ive got two hand held tds meters,one old and one brand new, and they both read different readings on my tap water by about 100 tds. so i was abit concerned that they may be giving false readings on my pure water even though they both say 000.
anyway what calibration solution do you guys use, as i have seen 342 and 20 tds solution, i presume i need the 20 because its nearer to pure or do you use both to to set the tds meter up accuratly. thanks

[jeff1]

No its the  342  that you use.

[steven ainger]

cheers jeff

[peekeclean]

why the 342 jeff? Iv done mine with the 20 and it made my handheld 5ppm would it be more with 342? i was suprised as my windows was drying crap at 001(befor i found it was 5 out).

[jeff1]

Its what the manufacturers recommend.

[steven ainger]

h ttp://www.ro-man.com/shop/product_info.php/products_id/250

this answers the question, calibration solution should be closest to what you are testing

[Jeff Brimble]

You get a good zero reading from triple distilled Vodka 
 

[john tomkins]

h ttp://www.ro-man.com/shop/product_info.php/products_id/250

this answers the question, calibration solution should be closest to what you are testing

Taken from RO-Man data on the TDS Meter they sell .....
" our meters are calibrated with a 342 ppm NaCl solution. Meters can be recalibrated with a mini-screwdriver"
also from HM site....
"HM Digital meters come factory calibrated (at 342 PPM)"

[steven ainger]

just because they come factory calibrated at 342 doesnt mean thats the best for us using 000tds water, probably better if your measuring tap water, thats why i posted  the link  earlier from the ro-man site.

[john tomkins]

just because they come factory calibrated at 342 doesnt mean thats the best for us using 000tds water, probably better if your measuring tap water, thats why i posted  the link  earlier from the ro-man site.

So the meters come calibrated at 342 from the factory, RO-man calibrates them at 342, but after asking, and being given advise  to use 342 , you are gonna go with 20ppm,
Your error according to your post was
"they both read different readings on my tap water by about 100 tds"
I'm presuming your tap water is closer to 342 than 20