jrpark22000
Premium member
A follow to my first thread on achieving testing accuracy in our tanks.
http://www.chicagoreefs.com/forums/...ous-about-water-testing-accuracy-Hach-DR-2000
This thread is only a supplement to the many other articles and info already on the web. It’s how I have taken the data from all of them and how apply it, sharing it in an all-inclusive thread. One such article is quite comprehensive, http://www.advancedaquarist.com/2002/1/chemistry.
Again I was striving to improve the testing accuracy as in my previous thread. With temp and salinity it’s much cheaper. First temperature; not all thermometers are created equally. There is no need to spend several hundred on a certified thermometer but a precision thermometer with a granular scale is a great investment. I picked mine up from vwrlabshop, but they no longer carry the model. A similar one on cole-paremer is $56 today, link below. If you look around you can find them cheaper. Either full immersion or partial immersion are available, I don’t have a preference. A good range is 30-124F as it gives an easy to read granular scale and being in F there is no immediate conversion for us in the USA.
http://www.coleparmer.com/buy/produ...r-30-124f-460mm-length-partial-immersion.html
Essentially, you should never need to worry about calibration of such a thermometer. It can now be your baseline to set the rest of your equipment to.
Now that temp is accurate we can move onto salinity. All salinity readings no matter the method are temperature sensitive. Some refractometers account for this, but they rely on an external fluid for calibration and they do not have a precision scale. When you factor in possible contamination of the calibration fluid, a refractometer is not accurate enough IMO. So, onto the precision floating hydrometer by tropic-marin.
http://www.tropic-marin.com/web/english/produkte/araeo.htm
If handled carefully it also is essentially lifetime calibrated. Simply by accounting for temperature you have all the tools required.
Taken from the above AdvancedAqauarist article;
How to Use a Standard Hydrometer
1. Make sure that the hydrometer is completely clean (no salt deposits) and that the part of the hydrometer above the water line is dry. Tossing it in so it sinks deeply and then bobs to the surface will leave water on the exposed part that will weigh down the hydrometer and give a falsely low specific gravity reading. Salt deposits above the water line will have the same effect. If any deposits won't easily dissolve, try washing in dilute acid (such as vinegar or dilute muriatic acid)
2. Make sure that there are no air bubbles attached to the hydrometer. These will help buoy the hydrometer and yield a falsely high specific gravity reading.
3. Make sure that the hydrometer is at the same temperature as the water (and preferably the air).
4. Read the hydrometer at the plane of the water surface, not along the meniscus (Figure 4; the meniscus is the lip of water that either rises up along the shaft of the hydrometer, or curves down into the water, depending on the hydrophobicity of the hydrometer).
5. Rinse with freshwater after use to reduce deposits.
6. Do not leave the hydrometer floating around the tank between uses. If you do, difficult to remove deposits may form over time.
View attachment 2131
You’ll also need to use the precision thermometer to know the water temperature. The tropic-marin hydrometer is calibrated at 77F and likely your tank is not at this exact temperature. A little math comes into play to adjust the hydrometer reading. The following conversion info was taken from CRC Handbook of Physics and Chemistry and on Bonython's research for ICI (1948.) I simply use google to convert the fahrenheit thermometer reading to Celsius for the calculation.
“For brines between SG 1.000 and SG 1.100 The difference each degree of temperature makes to the SG is not constant, however very approximate corrections are:
For every 5 degrees the sample is above the hydrometer's calibrated temperature, add 0.001 For every 5 degrees the
sample is below the hydrometer's calibrated temperature, take off 0.001 This is sufficiently accurate for temperatures
between 0oC and 40oC, but should not be used outside this temperature range.
A more accurate formula is:
Correction (to add on to raw hydrometer reading) = Raw SG + (0.00000359 x temp2 + 0.00006971 x temp - 0.00151687) temperatures are in Celsius”
My working formula:
1.0257 water at 79.2F(26.2C) with calibration at 77F(25C)
(1.0257 + ( (.00000359 x 26.2) + (.00006971 x 25) - .00151687))
..................(.......000094058...).+.(.....00174275...)
..................(........................001836868..................)
..................(.........................................000319938.......................)
(................................................1.02601........................................)
After a while a baseline of results for your tank’s temperature and salinity can be referenced and no longer need to do the calculation for each test.
My common results;
1.0246sg @ 80.4F(27C) = .00032281 Actual 1.02782
1.0255sg @ 77.2F(25.1C) = .000316348 Actual 1.02581 = 52.7ms
1.0255sg @ 76.8F(24.9C) = .000315271 Actual 1.02581 = 52.7ms
1.0256sg @ 76.9F(24.9C) = .000315271 Actual 1.02591 = 52.8ms
1.0257sg @ 78.8F(26C) = .00031922 Actual 1.02602 = 53ms
1.0257sg @ 79.2F(26.2C) = .000319938 Actual 1.02601 = 53ms
1.0258sg @ 77.4F(25.2C) = .000316348 Actual 1.02612 = 53.2ms
1.0258sg @ 78.3F(25.7C) = .000318143 Actual 1.02612
1.026sg @ 78.0F(25.5C) = .000317425 Actual 1.02632 = 53.5ms
1.026075sg @ 77.6F(25.3C) = .000316707 Actual 1.02639 = 53.7ms
I then take it one step further, yes even further…. Conductivity is more granular than typical SG readings and is far easier to test as compared to the above floating hydrometer. Details and review of the conductivity meter I use.
http://www.chicagoreefs.com/forums/showthread.php?18111-Equipment-review-Oakton-Conductivity-meter
To calibrate the conductivity meter to the floating hydrometer I reference;
http://www.americanmarineusa.com/salinityconversion.html
With a little more math, to convert SG into mS each .0001 sg equals ~.1625mS.
As a conclusion, All the variables in calibration of temp and salinity are in my control. I test right in my tank after turning off the flow. I don’t need to buy replacement fluid or worry about it’s accuracy. The tools, given proper care should last a lifetime. The thermometer comes in handy when calibrating my household thermostat and several other things whenever a questions about their accuracy arises. I know precisely what my tank temp is or any variation I may see in the results, it helps greatly in isolating defective equipment.
Questions, thoughts, corrections? What do you think?
http://www.chicagoreefs.com/forums/...ous-about-water-testing-accuracy-Hach-DR-2000
This thread is only a supplement to the many other articles and info already on the web. It’s how I have taken the data from all of them and how apply it, sharing it in an all-inclusive thread. One such article is quite comprehensive, http://www.advancedaquarist.com/2002/1/chemistry.
Again I was striving to improve the testing accuracy as in my previous thread. With temp and salinity it’s much cheaper. First temperature; not all thermometers are created equally. There is no need to spend several hundred on a certified thermometer but a precision thermometer with a granular scale is a great investment. I picked mine up from vwrlabshop, but they no longer carry the model. A similar one on cole-paremer is $56 today, link below. If you look around you can find them cheaper. Either full immersion or partial immersion are available, I don’t have a preference. A good range is 30-124F as it gives an easy to read granular scale and being in F there is no immediate conversion for us in the USA.
http://www.coleparmer.com/buy/produ...r-30-124f-460mm-length-partial-immersion.html
Essentially, you should never need to worry about calibration of such a thermometer. It can now be your baseline to set the rest of your equipment to.
Now that temp is accurate we can move onto salinity. All salinity readings no matter the method are temperature sensitive. Some refractometers account for this, but they rely on an external fluid for calibration and they do not have a precision scale. When you factor in possible contamination of the calibration fluid, a refractometer is not accurate enough IMO. So, onto the precision floating hydrometer by tropic-marin.
http://www.tropic-marin.com/web/english/produkte/araeo.htm
If handled carefully it also is essentially lifetime calibrated. Simply by accounting for temperature you have all the tools required.
Taken from the above AdvancedAqauarist article;
How to Use a Standard Hydrometer
1. Make sure that the hydrometer is completely clean (no salt deposits) and that the part of the hydrometer above the water line is dry. Tossing it in so it sinks deeply and then bobs to the surface will leave water on the exposed part that will weigh down the hydrometer and give a falsely low specific gravity reading. Salt deposits above the water line will have the same effect. If any deposits won't easily dissolve, try washing in dilute acid (such as vinegar or dilute muriatic acid)
2. Make sure that there are no air bubbles attached to the hydrometer. These will help buoy the hydrometer and yield a falsely high specific gravity reading.
3. Make sure that the hydrometer is at the same temperature as the water (and preferably the air).
4. Read the hydrometer at the plane of the water surface, not along the meniscus (Figure 4; the meniscus is the lip of water that either rises up along the shaft of the hydrometer, or curves down into the water, depending on the hydrophobicity of the hydrometer).
5. Rinse with freshwater after use to reduce deposits.
6. Do not leave the hydrometer floating around the tank between uses. If you do, difficult to remove deposits may form over time.
View attachment 2131
You’ll also need to use the precision thermometer to know the water temperature. The tropic-marin hydrometer is calibrated at 77F and likely your tank is not at this exact temperature. A little math comes into play to adjust the hydrometer reading. The following conversion info was taken from CRC Handbook of Physics and Chemistry and on Bonython's research for ICI (1948.) I simply use google to convert the fahrenheit thermometer reading to Celsius for the calculation.
“For brines between SG 1.000 and SG 1.100 The difference each degree of temperature makes to the SG is not constant, however very approximate corrections are:
For every 5 degrees the sample is above the hydrometer's calibrated temperature, add 0.001 For every 5 degrees the
sample is below the hydrometer's calibrated temperature, take off 0.001 This is sufficiently accurate for temperatures
between 0oC and 40oC, but should not be used outside this temperature range.
A more accurate formula is:
Correction (to add on to raw hydrometer reading) = Raw SG + (0.00000359 x temp2 + 0.00006971 x temp - 0.00151687) temperatures are in Celsius”
My working formula:
1.0257 water at 79.2F(26.2C) with calibration at 77F(25C)
(1.0257 + ( (.00000359 x 26.2) + (.00006971 x 25) - .00151687))
..................(.......000094058...).+.(.....00174275...)
..................(........................001836868..................)
..................(.........................................000319938.......................)
(................................................1.02601........................................)
After a while a baseline of results for your tank’s temperature and salinity can be referenced and no longer need to do the calculation for each test.
My common results;
1.0246sg @ 80.4F(27C) = .00032281 Actual 1.02782
1.0255sg @ 77.2F(25.1C) = .000316348 Actual 1.02581 = 52.7ms
1.0255sg @ 76.8F(24.9C) = .000315271 Actual 1.02581 = 52.7ms
1.0256sg @ 76.9F(24.9C) = .000315271 Actual 1.02591 = 52.8ms
1.0257sg @ 78.8F(26C) = .00031922 Actual 1.02602 = 53ms
1.0257sg @ 79.2F(26.2C) = .000319938 Actual 1.02601 = 53ms
1.0258sg @ 77.4F(25.2C) = .000316348 Actual 1.02612 = 53.2ms
1.0258sg @ 78.3F(25.7C) = .000318143 Actual 1.02612
1.026sg @ 78.0F(25.5C) = .000317425 Actual 1.02632 = 53.5ms
1.026075sg @ 77.6F(25.3C) = .000316707 Actual 1.02639 = 53.7ms
I then take it one step further, yes even further…. Conductivity is more granular than typical SG readings and is far easier to test as compared to the above floating hydrometer. Details and review of the conductivity meter I use.
http://www.chicagoreefs.com/forums/showthread.php?18111-Equipment-review-Oakton-Conductivity-meter
To calibrate the conductivity meter to the floating hydrometer I reference;
http://www.americanmarineusa.com/salinityconversion.html
With a little more math, to convert SG into mS each .0001 sg equals ~.1625mS.
As a conclusion, All the variables in calibration of temp and salinity are in my control. I test right in my tank after turning off the flow. I don’t need to buy replacement fluid or worry about it’s accuracy. The tools, given proper care should last a lifetime. The thermometer comes in handy when calibrating my household thermostat and several other things whenever a questions about their accuracy arises. I know precisely what my tank temp is or any variation I may see in the results, it helps greatly in isolating defective equipment.
Questions, thoughts, corrections? What do you think?
