2 tds meter questions....

[aquaman2]

......for 2 diff meters. i'm using the Hanna 800ppm calibration fluid and also confirmed calibration fluid temp to the proper cal. fluid tds value.

1. for the H&M inline (the one with the blue face). there is only one calibration screw. when i set the "in" probe to right reading (807ppm) the "out" was at 930ish. when i did the "out" probe and got it to 807ppm the "in" was at 930ish. am i missing something to calibrate this meter?

2. for the Hanna TDS1 handheld. used to work great, been awhile since i last used it. in the new calibration fluid it only reads 7 or 8 ppm, and turning the calibration screw dosent move it. batteries maybe????? or is it just broken?

[aquaman2]

???

[aquaman2]

has anyone had to calibrate the inline tds meter??? i know its a pretty common one. seems like someone would have run into this situation b4?????

[AZDesertRat]

I don't know how you would calibrate the inlines accurately at home. Unfortunately they depend on flow past the probe for accurate TDS measurements. You cannot just dip the probes in a glass, it won't work. The only way I see to do it would be to build a closed loop with 1/4" tubing and fill it with the calibration solution and a pump to circulate it past the probe.
I have two HM Digital inlines myself but I never depend on them for any level of accuracy. They are not temperature compensated so unless your water temperature and air temperature are exactly the same they will never be correct. The temp probe is inside the fat part of the probe right behind the little rectangular hole so is reading air temperature not water temperature. Ialways use my HM Digital COM-100 handheld since it is accurate and has a real temperature probe.