Hydrometer temperature correction
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Shirak
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Nice little handy calculator for SG temperature correction.
https://www.morebeer.com/content/hydrometer_correction_calculator
https://www.morebeer.com/content/hydrometer_correction_calculator
Shirak
Valuable Member
What is the standard SG at 18 C?
OP
OP
I made randys diy hydrometer standard so:
To produce a 3.714 weight percent sodium chloride solution, dissolve 1 teaspoon (6.20 grams) of Morton's Iodized Salt in 161 mL (161 g) of freshwater (making a total volume of about 163 mL after dissolution of the salt). This solution can be scaled up as desired.
I did this scaled up 5x. So 31 grams of salt in 805 g of ro water.
Shirak
Valuable Member
I was reading Randy's article on hydrometer and standards.
I think if you can warm it to 77-78 and then measure you should be reading 1.0264 SG using his 3.714 percent formula. That would give you the correction factor for your specific hydrometer.
"For standard floating hydrometers (Figure 2), which are not self-correcting for temperature variations, it is important to use the standard at the same temperature at which the aquarium water will be tested (within say, ± 0.5 ºC or ± 1 ºF). Preferably, that will also be the temperature at which the hydrometer is intended to be used (often marked on it), but that is not an absolute requirement. The aquarist can then mark on the hydrometer the level to which it rises (that is, the water line), and use that as an indication of the specific gravity of S=35 seawater, which has all of the properties listed in Table 1(specific gravity = 1.0264, etc). If the hydrometer reads higher or lower than 1.0264, then the aquarist can just imagine the scale on the hydrometer to be shifted up or down, and shift all other readings taken with it (at the same temperature) by the same amount."
I think if you can warm it to 77-78 and then measure you should be reading 1.0264 SG using his 3.714 percent formula. That would give you the correction factor for your specific hydrometer.
"For standard floating hydrometers (Figure 2), which are not self-correcting for temperature variations, it is important to use the standard at the same temperature at which the aquarium water will be tested (within say, ± 0.5 ºC or ± 1 ºF). Preferably, that will also be the temperature at which the hydrometer is intended to be used (often marked on it), but that is not an absolute requirement. The aquarist can then mark on the hydrometer the level to which it rises (that is, the water line), and use that as an indication of the specific gravity of S=35 seawater, which has all of the properties listed in Table 1(specific gravity = 1.0264, etc). If the hydrometer reads higher or lower than 1.0264, then the aquarist can just imagine the scale on the hydrometer to be shifted up or down, and shift all other readings taken with it (at the same temperature) by the same amount."
Shirak
Valuable Member
I am guessing your hydrometer is pretty close as the online calculators still say a hydrometer calibrated to 77 F and reading a solution at 18 C at 1.0284 would give a reading of 1.027 which is pretty darn close to 1.0264 So if anything it's reading around 0.0006 high
edit. ok so it's about 0.0004 high then?
edit. ok so it's about 0.0004 high then?
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Randy Holmes-Farley
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The calculators should be fairly close for correction. Seawater may be a little different than fresh water.
OP
OP
I used your chart for the tropic marin hydrometer in your article but it doesnt go below 23c so i had to figure it out. Is there a way to figure it out from the chart?
Randy Holmes-Farley
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It's better to use a calculator than extrapolate from a table.
I use this one, I can’t say how accurate it is, seems to be.
Salinity Correction Calculator
Aquarium calculator; Correct a relative specific gravity (sg) measurement taken with a non-temperature-correcting unit.
www.hamzasreef.com
