Met Instruments Flashcards
How would you read a precission aneroid barometer?
Press and hold the black switch button.
Turn know till light is continuous/borken.
Release the button.
Read pressure.
Apply corrections for height, index errror etc (not temp).
How would you maintain a precission aneroid barometer?
Change battery every 6 months or when light becomes difficult to see.
Calibration as per ordinary aneroid barometer.
What is the purpose of a barograph?
Produces a continuous permanent record of teh atmospheric pressure.
Enables observier to see barometric tendency at a glance.
No corrections required.
How would you maintain a barograph?
Installed horizontally on foam mountings.
Protected from excessive vibratin, direct sunlights, local heat sources and gusts.
No tapping for required for tendency.
Drum wound weekly.
Paper changed and set correctly (day and GMT) weekly.
No corrections.
What do we use to measure humidity at sea?
A hygrometer.
A wet and dry bulb hygrometer is called a psygrometer.
On board this is kept in a Stevenson screen.
This type is know as a Mason’s hygrometer.
How would you maintain a hygrometer?
Dry bulb kept dry and clean - if dried then leave for 15mins.
Wet bulb topped up with distilled water.
Muslin and water changed weekly.
How would you take a reading from a Mason’s Hygromter?
Take from windward.
Mariners handbook has table.
Plot the dry bulb against the difference to predict fog.
No corrections.
Ho would you use a whirling psychrometer?
In the shade.
180 RPM until consecutive readngs are within 0.1°.
Read wet bulb then dry bulb.
How would you measure the sea surface temp?
My last ship had a sensor which fed a bridge read-out.
OR
The bucket method takes water to the deck and temp is taken manually.
What methods are there of obtaining met info?
Radio. Telephone/fax. VHF. Navtex. Saftynet. Internet.
How does a barometer work?
Sealed aneroid cell responds to changes in atmospheric pressure by expanding/compressing.
These movements move a pointer.
Pointer indicates the atmospheric pressure to the observer.
How do we use an aneroid barometer?
Protected from excessive vibratin, direct sunlights, local heat sources and gusts. Gentle tap before reading. Avoid parallax error. No temperature correction required. Reading adjusted to sea level.
