How to Read a Galileo Thermometer and How Does it Work?

How to Read a Galileo Thermometer“See, all the bubbles are going up very slowly…”

“Wow…the red one is almost halfway down the water level so what is that?”

“Well, that indicates the ambient temperature of our room”

You guessed it right; those are going to be the sort of your conversations when reading a Galileo Thermometer with your mates.  For starters, this fascinating tool works on the principle of buoyancy i.e. –

Buoyant Force = (Fluid Density) x (Acceleration Due To Gravity) x (Fluid Volume)

With the invention of digital temperature sensors, Galileon Thermometers have mostly become the pieces for decoration. However, some people still enjoy reading the temperature with it. Although the results aren’t very accurate, measuring ambient room temperature is quite amazing!

If you’re about to explore one, so wondering how to read a Galileo Thermometer, your search has to come to an end. Stay tuned…!

What is a Galileo Thermometer?

What is a Galileo Thermometer

“Density of a liquid changes in proportion to its temperature” - Galileo Galilei

Galileo Thermometer is made based on this principle and named after Galileo. He first invented a thermoscope in the early 1600s.

However, the thermometer is also known as a Galilean or barometric thermometer. It’s made of a sealed glass tube filled with water having glass bubbles/vessels/spheres floating in various levels of the liquid.

Initially, the bubbles aren’t essentially made to be exactly the same size and weight. But once filled with varying food-colored water/alcohol, they’re calibrated to weigh the same. The coloring helps to easily identify them and adds beauty to appearance.

Next, each glass bubbles carry a temperature tag made out of metal. They are calibrated counterweights so have slightly varying densities. And specific temperature digits are engraved on it. So finally, the vessels will have the varying density to float.

Density = Mass/Volume

How Does a Galileo Thermometer Work?

Basically, it indicates temperature by the floating position of the vessels. As the temperature of the environment rises or drops, it affects the liquid’s density inside the glass tube.

The density will increase or decrease resulting in some bubbles floating while others sink due to proportional density. It mainly happens due to the gravitational downward force also referred to as the principle of buoyancy.

However, if you still wind up with any questions, feel free to leave them below in the comment box. We’ll reach out to you with the best possible solution

So spheres that are denser than the water will sink. And those less dense than water will float. Hence, the bubble tags that you read will indicate temperature. And the value might fluctuate a little bit so you get an approximate result of the current situation.

Note that the vessels are made in a way that the colored liquid inside is very less affected by the change of temperature of the thermometer.

How to Read Galileo Thermometer: Easy Guideline

How to Read Galileo Thermometer

Now that we know how a Galileo Thermometer works, it’s time to read temperature with it! Note, when the temperature rises, density of the water will decrease.

Contrarily, when the temperature falls, water density will increase. So the spheres will float more when it’s cold outside subsequently, sink more in hot summer.

With that being said, these are the exact practical steps you need to follow –

Get the Right Thermometer

These analog tools are made to measure a varying range of temperatures. So they aren't the same and are limited within the specified range.

Most of them can read between 64-80 degrees F. However, you may find others to read between 60°F to 100°F range. So make sure you fit in the right product to have an accurate measurement.

Placing in a Suitable Location

If you’re about to measure air temperature indoor/outdoor, hang it on a hook in the air. Remember, holding in your hand might not bring accurate results because your hands will transfer temperature to it. Or, if it is to check water temperature, put the thermometer in it.

Reading a Galileo Thermometer

Lets say, you have a Thermometer with five bubbles/vessels. Each of them carries a specific temperature tag as follows –

  • Yellow vessel = 65°F
  • Purple vessel = 70°F
  • Green vessel = 75°F
  • Blue vessel = 80°F
  • Red vessel = 85°F

Again, all of these vessels/bubbles calibrate the galileo thermometer in a way that the Red is the lightest while the Yellow is the heaviest one. Assume that you're measuring room temperature which is around 75°F.

Now, allow the thermometer about 4-5 minutes to work. Added to that, the spheres will get to their floating or sinking position. So at this stage, the Yellow and Purple bubbles will sink because of higher density at your room’s temperature.

On the other side of the pond, Blue and Red vessels have a lower density than the liquid. So they'll be floating at the top of the water.

And lastly, the Green sphere has a very similar density to the water. So it'll indicate your room's temperature with the tag 75°F and will be floating almost halfway down.

All in all, reading with a Galileo thermometer isn't very accurate compared to a digital thermometer. The reading might be ±4 °F depending on its precision. But it's obviously an amazing ancient technology with a wonderful appearance.

1. Value Averaging

Most of the time, some of the spheres will be floating and some will sink leaving some to hang halfway down. Hence, the reading is what we see in the middle of the tube.

But when there’s nothing in the middle, you’ll have to calculate the average. Note down the lowest floating vessel plus the highest sinking vessel’s temperature. Now, divide their summation and that’s the result.

Temperature = (Lowest Floating Temp + Highest Sinking Temp)/2

2. Reading Cold and Hot

If all the spheres are floating at the top of the water it means your room temperature is even colder than the highest tag. Hence, water particles are in contract with less distance among them.

On contrary, all spheres sinking indicate a hotter temperature than the lowest tag. Although it might not be able to tell you the exact value, it’s a good sign of the threshold.

Tips for Getting Perfect Measurement

It can be a little bit confusing when using a Galileo Thermometer for the first time. That’s why we've laid this section with some exclusive tips to get reliable temperature readings. Let's get to that –

  • Purchase one that has a wide measurement scale
  • Don’t hold the thermometer in hand when it’s in action
  • Allow it enough time (around 5-10 minutes) to read temp properly and let the spheres change their position accordingly
  • Use the averaging formula to calculate the value manually when possible
  • Lastly, remember that quality tools come with high precision

Galileo Thermometer Not Working: [4] Common Problems and Their Solutions

Galileo Thermometer Not Working

Being an analog temperature measurement tool, it’s very common for a Galileo Thermometer to get stuck or not produce the results expected. If you're into any of these below-mentioned troubles, you'll love the solutions –

Problem 1: Bubbles are wedged

Since there are around 5 – 8 glass bubbles, it's common to have them wedged because of leaving them one-sided/tilted for a long time. Or, they might also get surrounded during your product packaging and shipping.

Hence, the solution is to wiggle the tube very carefully and try to separate them. Be highly careful and delicate otherwise, you might break it. Gently tap on the glass and it should untangle them.

Problem 2: Bubbles aren’t floating

This can be the reason that the temperature lets them sink at the bottom. Hence, the water density is less than all of the spheres meaning a comparatively hotter temperature. However, if you’re sure that the reading isn’t correct and there’s something wrong, here’s how you check;

Keep the thermometer in the fridge for about 10-15 minutes so water density rises. When you get it out and still the bubbles aren't floating, it's a faulty tool!

Problem 3: Bubbles aren’t sinking

It’s the same case like we’ve described in Problem number 2 above. If you’re sure about its fault so wondering why the spheres aren't sinking, put it into a beaker filled with hot water. This will raise the temperature of the liquid causing to decrease in density. Now you should start to see them falling down.

Problem 4: Sphere calibration affected

It might happen if the thermometer is kept in an unfavorable environment. Such as, under direct sunlight the liquid of the spheres might experience some chemical changes. At this stage, they’ll lose the calibration eventually resulting in the loss of measurement accuracy. So the best possible prevention of this problem is to maintain the tool in a favorable environment.

People Also Ask:

1. What is the clear liquid in the glass tube?

The liquid inside the thermometer is water mixed with ethanol. So the density is a little less than that of only water.

2. How do you read a Galileo glass thermometer?

The ambient temperature is determined by the vessel floating in the middle of the tube. If there’s nothing in the middle, spheres might be in three other positions.

First, they’re divided into groups having one floating and the other group sink. Hence, calculate the average by using the lowest floating and height sinking values.

Secondly, if all spheres are floating, the temperature is colder than the highest tag. The third position is that all spheres are sinking meaning an even hotter temperature than the lowest sinking value.

3. How accurate is a Galileo thermometer?

As we already have mentioned earlier, the temperature reading isn’t very accurate with this tool. However, it’s a great point of approximation. And for ambient temperature, it gives a close to accurate result with ±4 °F fluctuation.

4. Can a barometric thermometer freeze?

No, it does not freeze! But it's advised not to place the thermometer under direct sunlight. This might affect the nature of the liquid inside the spheres. Eventually, it affects their calibration and harms measuring accuracy.

Final Words

In the end, we believe that we've sufficed your query on how to use a galileo thermometer! All of the above-mentioned practices are very practical that'll make your way easier than you could think.

Remember that reading a Galileo thermometer isn’t like rocket science. It shouldn’t really bother you that much. But you’ll have to get used to it over time. Soon you’ll start to see things are coming much easier and enjoyable!

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