1. Manometer
Man questions – depending on your answer, the meter will go up or down
1. How many times a week do you shave your face?
2. Have you ever shot a gun?
Then actually hit your target?
3. How many times have you wrestled a bear?
An older relative?
And won!
4. Do you emit gasses from your body in public on a daily basis?
5. Have you been caught down town wearing a dress?

2. Manometer
Pressure
What is pressure?
What creates atmospheric pressure?
How do we measure atmos. Pressure?

3. Mercurial Barometer - operates from
the response of Mercury (Hg) to air
pressure

4. Aneroid Barometer; means without liquid;
operates with a vacuum chamber and air pressure

5. Pressure Units of measure 1 atmos = 760mmHg 1 atmos = 101.3 kPa
1 atmos = 1, mb
Say What?
(1 atmos = about 14 lbs / in2)
Pressure = Force / area
1.0 Pascal = 1.0 N/ 1.0 m2
A Newton is a force; (= ¼ pound)
1.0 N = 1.0 kg x 1.0 m/s2
Area – meters squared, 1m * 1m = m2

6. Converting bars to millibars or millibars to bars; converting Pascal’s to bars, or bars to Pascal’s
Essentially . . .
1. What’s a bar of pressure?
1.0 atmosphere of pressure = 1.0 Bar
Given: 1.0 atmos = 1,013.0 mb
1.0 millibar = atmos pressure
You’ll have to assume its the same as 1.0 atmos = bar
To convert back to millibar; move the decimal three to the right; so bar = 1, mb
Or recall 1 milli of something is 1/1000th (0.001) of a bar but will be presented as 1.0mb
2. Bars to Pascal’s; 1Pa = 1.0N / m2
Given: 1 atmos = kPa
If we just have Pascal’s; How many Pascal’s are in one atmosphere?
Essentially . . .
1.0 atmos = 101,300 Pa – this is the base unit, a value of 1.0
Meterologist will use the kilo Pascal; so that’s a 1000 Pascals. To convert from
a Pascal to kilopascal, you’ll need to move the decimal three to the left.
101,300Pa = kPa
So: 1.0 bar = 101,300 Pa

7. But . . . What do the meteorologist use? millibars and kilopascals.
Given: 1 mbar = hPa; meaning one millibar equals 100 Pascal’s OR 1/10th of a kPa.
Here’s the breakdown:
1.0 bar = 101,300 Pa
Often written as: mb = 0.1 kPa
How do we get that?
Convert the bar to millibar; do the same to the other side
Move the decimal three to the left for the bar and the Pascal
From: Bar to millibar
0.001 bar
What’s done to one side of an equation must be done to the other side!
101,300 Pascals will become Pa
Now it’s 1.0mb
1 mb = Pascals Which can be expressed as 1mb = 1 hPa
But – the scientist decided to go ahead and make 1mb = 0.1kPa ( 0.1 kPa = 1.0 hPa)
Check your understanding!
1. How many millibars will be in one kPa?
= _____mb 10
atmos. = kPa = __________ mb
1,000

8. In Summary or to simplify just remember
1 atmos =
1.0 Full bar
= 101,300 Pa
These are all the base units!
STP is one atmosphere of pressure at 0° C. Since this would be a freezing temperature at sea level, most of the time dry air is less dense than the cited value. However, air typically contains a lot of water vapor, which would make it more dense than the cited value.
Atmospheric Pressure
Units of measure
1 atmos = 760mmHg
1 atmos = kPa
1 atmos = 1, mb OR 1.0 bar
To complicate everything check out all the atmospheric conversions