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New EC Meter Issues

Scuba_Steve

Scuba_Steve

So I finally am getting my hydro up and going. I mix up some ferts from DIY salts. I am weighing on a 0.01g scale, so I should be pretty accurate.

I make my ferts in a 2 part, 1:32 ratio spread across 2 gallon jugs. So 1/2c of A, and 1/2c of B to mix 1 gallon of ferts. I ensure they dissolve very well.

According to Hydro buddy, I should be at an EC of 1.7.

My tap EC is 0.24 according to my new meter. My final EC... 3900 uS/cm or 3.9 mS/cm. TDS on the other hand is 1900ppm. I break out an old TDS meter, and it registers as 1240ppm, which converts to 1.77 mS/cm. That is pretty much exactly where I was expecting.

Tap sample is very similar. 140ppm on the new meter, 124 on the old one.

Bad meter? It is a cheap amazon one. Can I make a calibration solution to verify?

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there are 2 widely used conversion constants for "ppm". have you accounted for that?

idk what they are. ive been using ms/cm for so long, its the industry standard far as i know.
err us/cm.
 
3 ppm standards actually, but yes I did.  The conversion factors from uS/cm to ppm are 0.5, 0.64, and 0.70.  So if my meter was reading 3900 EC that would correspond to 1950, 2496, or 2730.  The old meter ran much lower than any of those.
 
Scuba_Steve said:
Can I make a calibration solution to verify?
Click to expand...
Add 0.491g of NaCl to a clean, accurate measuring container, top up to 1000ml with distilled water. TDS: 500mg/L (ppm), EC: 1.0
Alternatively, add 1.005g of NaCl for TDS: 1000mg/L , EC: 2.0
Note the EC`s are related to 0.5 scale, which is probably the most common.
 
just buy a calibration solution bottle for which ever one you value the most... calibrate it, then trust that one.

ive had the same calibration solution bottle for like 5 years so get the smallest bottle possible. a few foil packets even... if they are reasonably priced(often are not).
 
A 1.005g NaCl solution made from table salt and distilled water using a 20g x 0.001g scale gives a TDS of 1007 which is comparable with +/- 1% store bought solutions. With a 0.01g scale, Steve`s margin for error will be higher but it`ll be good enough for his verification purposes.
 
dude a bottle of calibration solution is 10 bucks.
 
i have an ohaus dial-o-gram thats accurate to .01... but even so i would not bother trying to make a calibration solution.  just get the manufacturer approved calibration bottle or sachet.
 
Thanks,
 
I needed immediate results to determine how much ferts to add within the next day or so.  While amazon ships fast, I prefer to have them faster.  Plus I just needed to get a ballpark.  After all, the EC reading is almost double between the two meters. 
 
Well, using the 1.005g EC 2 solution, my new meter read 2005.  Now I am wondering why my mixture is so far off of what Hydrobuddy suggests it should be!  At least I can adjust fire now though, and know that I can trust my meter.  The older meter is going in the trash!
 
I didn't. Measured to the centigram. Again, I just needed a ballpark. Neither of mine are calibratible, so having an exact reference isn't needed. I just needed to know which of the two was obviously off.

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