Tuesday, July 19, 2011

Prevent mold! Hygrometer Calibration

I work with often in my role as a hygrometer home inspector. Quality hygrometer consumer and / or measuring relative humidity readings are inexpensive and notoriously inaccurate. This is a shame, because they maintain the proper humidity in your home is a good start to discourage the growth of fungus or mold. Mold is perhaps difficult to identify and is usually excluded, home inspection reports. However, if an inspector sees the form he or she will mention in the rule. Most experts, Suggest that the relative humidity is kept in a house between 30% and 50%, with 60% rarely a cause for concern. You can go online and find hundreds of articles explaining the reasons for this and offers readings for optimum climate. You could also get that information from a university counseling service near you. Having this goal percentage, especially for this climate and region, the simple steps below, you can ensure that the measurementsContact your hygrometer is properly and correctly at all times.

Calibrate a hygrometer:

Humidity Control Chamber

If you want to have a digital hygrometer to measure humidity and or to calibrate accurately, without having to buy expensive calibration kit supplier of salt, here is the easy solution. The physics behind this project is simple and reliable: different salts, when mixed with water to create mud and sewage, produces a constant and predictableHumidity.

Simplified scientific explanation:

A saturated solution at a stable temperature and pressure has a fixed composition and pressure of steam drive. Thus, in a constant temperature, no matter how much salt and how much water is present, the (RH) relative humidity, which is produced determines how long are the water and the solid phase is present. So, unless the water dries, the salt is or becomes so wet that liquid may have a certain moisture products.

Theis convenient for us that a solution of common salt with water (preferably distilled water) produced a predictable mix of moisture in a wide temperature range. The moisture created by common salt (sodium chloride) and water is 75.29% at an ideal temperature of 77 degrees Fahrenheit. The room temperature is not crucial for our purposes. For example, the relative humidity is quite stable, even with large fluctuations: saline at 59 degrees Fahrenheit and produces 75.61% relative humidity at 86Degrees Celsius, relative humidity is 75.09%.

To calibrate the lower end, 33% humidity, magnesium chloride (a salt) and water is reused. The ideal temperature of 77 degrees Fahrenheit, this solution will produce a relative humidity of 32.78%. At 59 degrees Fahrenheit, it produces a relative humidity of 33.30% and to 86 degrees Fahrenheit will produce 32.44% RH. Once again, "room temperature" is not critical.

Detailed calibration procedures:

For the majority of professional tools, we recommendboth a nadir and a higher point of reference to be calibrated. For simplicity, most manufacturers have chosen 75% and 33% RH calibration standards as standard. Therefore, to calibrate our instruments, we must be able to own the equipment in our "wet room" instead.

To create a humidity chamber with 75% salt in a container and mix with a little 'of water - but not too much. You want a wet mud, not soup. I made pots of yogurt container. I cut the tips so thatare about two inches tall and trim recessed area so that the hygrometer can rest with the sensor on the solution, without direct contact with the wet solution.

Place the hygrometer on the yogurt and seal it in a cup or two Ziploc bags. After a little 'air in the bag and the end is inevitable. This method should work with any hygrometer, including the favorable mechanical hygrometer, which is usually only checked or calibrated to 75%. Even in this caseAccommodation to ensure that the device does not get wet - it has the sense of water and relative humidity not. Normally, the hygrometer with more convenient, you can not actually calibrate the device by default, but you can take a reading to a known relative humidity and calculate a correction factor. If you use a simple tool like this are precisely calibrated to 75%, obtained by the correction factor for future reference, and work from there. Should be close enough to their needs.

NOTE:If you are a professional electronic hygrometer, which have a built-in sensor, but accessible, it is possible to simplify the calibration. Only get a couple of plastic cups, or similar foods such as oysters come in and drill holes in the lid to provide a comfortable fit for the sensor on the instrument. Label the jars of 75% and 33% and adjust the salt mixture into the glasses. I still use the cup of yogurt for mixtures of salt and jam in a firm grip, about 1 / 3 of the way into the pot, so that amoist chamber is formed near the top of the jar. Screw the lids on the jars. If you have two hygrometer, put a lid on each jar. Otherwise, put your hygrometer in a glass lid and a piece of tape or a seal from one species to another, so that will stabilize the RH. Once the correct relative humidity was created as described in the same period of time in a row, you can quickly check or to calibrate a hygrometer sensor in one of two glasses. Always provide a tool for some time, If you stabilize the moisture from one room to another. This is the most accurate method to calibrate an instrument for you, if you can do it that way. The readings will remain stable as used in a plastic bag: a bag when it is compressed by mistake or moved the content, what will happen if you calibrate the device, rather than consider them, have the stability of the moist chamber is concerned, and that can lead to calibration errors. Consequently, itProcess must be done carefully and rechecked.

Chemical solution 75%:

Use the pure salt, sodium chloride - no additives. Morton Salt preserves from the grocery store is a salt, and is inexpensive. Put a few spoonfuls of yogurt cups, and distilled water to a paste. Put them in a plastic bag is placed over the container with the hygrometer, and let stand for about 12 hours. As long as it takes to stabilize the solution. (I leave to stand overnight.)Personally, I like to see the hygrometer so you can see through the bag reads, as they can be changed, so I know when the solution has stabilized.

With more digital hygrometer, must be calibrated with the power or the display off. He, therefore, if the solution for 12 hours and stabilized, of course, I turn off the unit. Then I start with the factory calibration process. These impressions usually with a paper clip orsimilar object, a button and other controls embedded in a fixed order. In essence, it is to "teach" to "recognize" the instrument has a number next to the moisture, is exposed. With the plastic bag, you can use the hygrometer and the controls are adjusted so that a simple thing, a small hole in the pocket with the clip and the instrument, without the humidity that created it.

Chemical solution 33%:

You need magnesium chlorideHexahydrate. This is not easy to obtain as a saline solution, but it is not difficult to find and it certainly can be done much cheaper than buying the kit calibration salt. Prices and availability change, but I can buy small amounts of magnesium chloride hexahydrate, professional quality flake on eBay. It will not be much at once, but hygrometer should be calibrated twice a year, he will have an offer worth of hand. It 's always difficult to buy even simple chemicals,but can be found at chemical supply houses online. It 'also used as a defrost. (Do not buy a supplement of magnesium chloride in an organic food store + -. wrong product) a mixture of magnesium chloride hexahydrate in distilled water, in the same manner as described above, and follow all procedures themselves. You can use both pockets, 33% and 75% were started at the same time, and place the instrument in one. This can stabilize both solutions at the same time and need to begin the production of relative humidity.After the first calibration, open and quickly put the hygrometer in the bag next. Allow some time to stabilize. This can last from 40 minutes to six hours. You can tell when it is ready for calibration, because reading is the same for a long time. Fill in the second calibration and you are done for six months!

Note: If you want to verify the accuracy of the instrument, other salts can produce many different RH. The procedure, with regard to the mixingsalts and water and creating a room humidity control are the same as described above.

6.37% lithium;
Lithium chloride, 11.30%;
Potassium acetate, 22.51%;
Potassium carbonate 43.16%;
Magnesium nitrate, 52.89%;
57.57% sodium;
Potassium iodide, 68.86%;
Sodium chloride, 75.30%;
Potassium chloride 84.34%;
Potassium sulphate 97.30%

And 'possible to use theseCalibration with a hygrometer, whether or not it can be calibrated to determine, this is how we can mathematically correct for inconsistencies. For example, if the machine reads 80% humidity to 75% in the saline solution, is to be read from 6.0 to 7.0% too high, and this should be considered when future readings are taken. Usually with a mechanical device, is to read only 75% being tested. Some people get a hygrometer, by testing it in a wet towel and afterfew hours, if the value of 98%. One problem is when the unit is set too high to read, and shows a reading at the top of the ladder - which seems reasonable if it is in a wet towel - the device may actually be at 110% or even 120% detection but this is not obvious, since the reading of the scale. Therefore, a second reading, shows that 50%, actually 20 points. E 'for this reason that the last two calibration points, which are both easily recognizable onDisplay of the instrument were established by the manufacturers.

Prevent mold! Hygrometer Calibration


  1. Great thoughts you got there, believe I may possibly try just some of it throughout my daily life.

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