Best Sling Psychrometer
If you're not a weather person, then it's very unlikely that you know what a psychrometer is. But if you could, we bet you'd like to know, because it's quite a handy little tool for atmosphere enthusiasts. We have introduced below five of the best sling psychrometers. But before we get to them, first let's discuss what a psychrometer is, how it works, and how to read a sling psychrometer.
What is Psychrometer?
A psychrometer is actually not as complicated as its name sounds. It is, in fact, a simple type of hygrometer (a device used to measure the amount of humidity in the air). A sling psychrometer is a psychrometer that is rotated in the air.
How Does a Psychrometer Work?
A psychrometer uses two thermometers to measure the humidity in the air.
1. Dry bulb thermometer - used to measure the temperature while the bulb is exposed to the air.
2. Wet-bulb thermometer - used to measure the temperature while the bulb is dipped in a liquid.
The difference in both the temperatures is used to determine the relative humidity of the surrounding area. But how?
When water evaporates, it cools down the surface of whatever object it was on. This is because when water turns to vapor, it uses heat to vaporize, and when it evaporates off the surface, it takes away the heat with it. But if the air is already humid, water won't turn to vapor because the air is saturated and already holds as much water vapor as it can; the water will remain on the surface of the object as water droplets.
The two bulbs of the psychrometer are used to determine how much water evaporates into the air, and thus, the relative humidity. The dry bulb thermometer (which is basically a regular thermometer) is exposed to the air and measures the temperature. The wet-bulb thermometer has a cloth wick wrapped around its bulb and is kept dipped in a liquid until you want to measure the humidity.
When the wet-bulb is taken out of the liquid and exposed to the air, the water starts evaporating. As it evaporates, it cools the bulb down. The drop in temperature tells you how much water has evaporated. As a result, you can determine how much vapor was in the air by calculating the difference in temperatures of the two bulbs.
Moist air allows very little evaporation while dry air encourages more evaporation, cooling the bulb down considerably as it absorbs more moisture.
This principle of evaporation allows the simple psychrometer to tell the relative humidity in the air. It also makes for a simple, efficient, and easy-to-use tool for humidity measurements.
How Do You Read a Sling Psychrometer?
Both thermometers are attached by a dowel and screw and swung through the air for one minute. Once done, the temperatures on both are recorded, and the difference in temperatures is calculated.
There is a chart that comes with psychrometers. Find the relative humidity by plotting the dry-bulb temperatures on the y-axis and the difference in temperatures on the x-axis. The point where they meet is the relative humidity (as a percentage). However, most psychrometers now come with easy calculation methods instead of charts.
The Best Sling Psychrometers
Below are some of the pros and cons of the top 5 psychrometers on the market.
1. Bacharach Red Spirit-Filled Sling Psychrometer 0012-7012
The Bacharach Red Spirit-Filled Psychrometer is one of the best in the market. It measures RH from 25 to 120°F and is accurate to 1°F. It weighs 1 pound, and its dimensions are 7.5x1x1 inches. The sling psychrometer is easily rotatable and measures the relative humidity with needing to consult complicated tables. It contains a slide rule calculator that allows you to read the wet and dry bulb readings accurately. The psychrometer does not come with a case, but it includes a protective covering for the thermometer. Simply slide it into the vertical part that acts as the handle - it is essentially a hard plastic case! The instrument includes a small reservoir for distilled water, so you don't have to wet the wick every time. All parts can be replaced by Bacharach with a warranty of 1 year.
Because the Bacharach model uses alcohol instead of mercury, it is not advisable to use under extreme temperatures as it can cause the liquid to separate. The psychrometer should be stored away when not in use and kept away from direct sunlight; otherwise, the liquid will bake. The Bacharach does not come with a calibration certificate, but the slide rule works well. You may also buy a psychrometer chart for more accuracy.
2. Sling Psychrometer (-5 to 50°C)
This basic but efficient sling psychrometer comes with a protective carrying casing and a plastic humidity reading chart. It uses a red-colored liquid that is safe and easy to read (eliminating the hazard of using mercury). The sling psychrometer provides accurate readings within the range of -5 to 50°C. It weighs 0.24 pounds, and the dimensions are 8.5x6x1 inches. The thermometer can be safely recessed into the protective plastic mounting for protection and comes with a water reservoir that allows the wick to remain wet for days without needing a refill.
This sling psychrometer comes with a 90-day warranty (shorter than the Bacharach), but it is more efficient, lightweight, and has a higher rating than the Bacharach. Costing $89, it is slightly expensive, but the user gets what they pay for - a fast and accurate instrument with the necessary accessories needed for calculating the relative humidity and keeping the psychrometer safe.
3. Taylor Precision Products Sling Psychrometer
This psychrometer, which retails for $82.95, is just the thing for professionals on the go. It is a compact and highly accurate tool and can measure temperatures between 20 and 120°F. The psychrometer has a slide rule printed on the outer casing, which accurately reads temperature-to-humidity conversions. The humidity percent scale is 10 to 100 percent, and the permacolor display provides quick and easy readings. The case is made of durable plastic and is lightweight, making it easy to travel with. The instrument comes with six measuring wicks.
However, the rod and the instrument are not locked together, only fitted together. So there is a chance that once you start spinning the apparatus, half of the item might go flying off and hit something. That's definitely not something you'd want in a sling psychrometer. It also makes noise when you spin it and is a bit tricky to assemble, and if you apply too much pressure while assembling, the plastic might crack. But the price is good for the benefits it gives, and it works as well as a psychrometer should in terms of relative humidity readings.
4. Yellow Jacket 69010 Sling Psychrometer 0.01%
One of the more expensive psychrometers, this Yellow Jacket sling psychrometer retails for $118.84. It does not contain mercury, which makes it much safer to use than those thermometers that do contain this toxic element. The best thing about this model is that it's small enough to fit inside your pocket - a handy, traveling psychrometer! Cool, right? Its dimensions are 6x3x1 inches, making it one of the smaller psychrometers out there.
It has a calibrated scale rule built into the body, which makes it super easy to read the relative humidity readings on the go. It's accurate to 1% of hygrometric tables and has a corded electric power source. The wick gets wet very fast, which means that you get immediate results and don't have to wait too long for reading. It weighs 0.34 pounds and is very easy and convenient to carry around. The only downside is that with a scale that small, you might have to squint a bit for the reading. But other than that, it is an excellent instrument that is worth the money.
5. Sling Psychrometer (20-120°F)
This sling psychrometer weighs 0.24 pounds and is 8.5x6x1 inches long. It can measure temperatures ranging from 20 to 120°F and is an efficient tool for measuring the relative humidity of the surrounding atmosphere. It costs $89, making it one of the mid-ranging psychrometers in terms of pricing. This model of the sling psychrometer uses a red liquid (alcohol) in its thermometers that make it easier to read and safer to use than mercury thermometers. It comes with a plastic humidity reading graph and a protective plastic casing to keep the instrument safe from breaking.
The thermometer can be stowed back inside the plastic handle, making the instrument more compact, and the thermometer more protected. It comes with a water reservoir which keeps the wick wet so that it can give immediate results at the time of use. This psychrometer is highly rated and is lightweight and efficient, too, making it ideal for frequent use. It comes with a three-month warranty, and for the price and specifications it offers, it's one of the best instruments available in the market.
Author: SectionCut Team