Hey All,
I finally bought a DOS pump with the intention of setting up an AWC system. I went through and calibrated with a lab grade glass 50 mL graduated cylinder. I'm set up to remove 1250 mL from my tank from 7:00 to 7:30 and then add 1250 mL from 7:31 to 8:00. I have a Tunze ATO that is disabled during this timeframe.
I watched the pump the first day and there is a fairly significant deviation in the water column level in the before and after tank quantity (note: I manually disabled the ATO for the entire timeframe so it isn't skewing the outcome). So I decided to try calibration on a larger scale, thinking that any error is amplified as total dosed volume increases.
I reset the calibration to 40.0 and moved up to a 250 mL graduated cylinder. I programmed the Apex to dose 240 mL of new salt water over a 10 minute period. I get 243.5 mL. I ran this three times for consistency and each time was within about 0.50 mL by line of site.
So next, I looked at a ratio of what my calibration numbers should be. Here's my math:
X mL / 40 mL = 243.5 mL / 240 mL, with X being the number that should be entered in the calibration screen. This gives me X = 40.6 mL. Next, I ran through the calibration program again, discarded whatever 40 mL it tried to dose and entered 40.6 as the actual dosed amount. So I run my 240 mL test again and get a wide variety of numbers, within about 5% of target.
I reset the calibration back to 40.0 and ran to the original 240 mL test a second time (test that consistently yielded 243.5 before). Now I'm consistently getting 230 mL from a 240 mL dose. This is a 5% error from what I was getting previously.
I've always heard I could expect accuracy within 1%. 5% seems incredibly high. On a 1250 mL daily water change that will put me +/- 4 oz, which could affect my salinity on relatively short order.
Is there a way for me to see the calibration multipliers that the Apex is using? Every time I go through the calibrate menu it sets back to 40 mL for the test, making it difficult to make micro adjustments.
Thanks for any thoughts all,
CS
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