Casella CEL Fortin barometer - Manual (Page 4)

HB3121
4
INITIAL SET UP
CHOOSING A SUITABLE LOCATION
The room in which the barometer is due to hang should: -
•
Not be unduly warm.
•
Not be subject to variations of temperature.
•
Not be exposed to sunlight.
•
Not contain corrosive chemicals.
•
Not be used as a passage way to other rooms.
•
Have solid walls free from vibration.
•
Be well lit using artificial light if necessary.
UNPACKING
Unscrew the barometer board from the back of the packing case, lift the complete
instrument on its board out of the case and lay it on the bench, with a block 8 –
10cm high, under the cistern end.
Then remove the barometer from its board by unscrewing the top and bottom
holding screws, and place it by itself on the bench with its cistern resting on the
block.
CHECKING FOR AIR IN THE COLUMN
Before hanging the barometer on its backboard, it should be tested to ensure that
no air has entered the vacuum space at the top of the mercury column.
To do this the barometer should be slowly raised to a vertical position with the
scale uppermost. This is to be the position in which it will finally be used.
It should now be possible to see that there is a space between the top of the
mercury column and the top of the glass tube. If there is no space visible, unscrew
the milled-headed screw at the base of the cistern several turns. This will lower the
mercury column and create the required space.
Next slowly incline the instrument away from the vertical until the mercury
touches the end of the tube. When this happens a sharp metallic click should be
heard, if only a dull thud or no sound at all is heard it is indicative that air has
entered the column. If this is so, please refer to NOTES section.