Instructions for Setting up the Micro-Barometer

INSTRUCTIONS FOR SETTING UP THE MICRO-BAROMETER

The instrument should be hung by means of the hanging plates attached on strong nails or screws, firmly inserted into a wall as

free from vibration as possible, and where the direct rays of the

sun, or sudden changes of the temperature are not likely to affect

it. The case should be carefully levelled and should hang plumb

in order that the pendulum may swing freely.

After fixing, cut away all thread or string used to hold the

parts in position during transit. Release the pendulum, and the

weight from their fixings, set the pendulum swinging, and wind the

weight up a short distance, being careful to see that the cord has

not got off the pulleys or winding drum. Always hold the edge of

the paper cylinder steady with the finger when winding up the weight.

the paper is attached to the lower cylinder by simply pressing it in

to two small pointed hooks, be careful to keep fingers from being

torn by these hooks, when cylinder is rotating without the paper

being attached.

The brass spool on which the roll of paper is carried, is in

the upper part of the case, and its pivots are running in V bearings,

from which it can be removed by moving upwards and backwards, and

then bringing it out downwards. This spool need not be removed until

all the paper has been run off, when the method of taking it out,

and replacing it, will be better observed. The paper is driven by

means of a small brass pinion extending on a rocking frame from the

clock-work. The spindle of this pinion is weighted by a brass disc

in order that the pinion may grip the surface of the paper. The speed

is thus irrespective of the varying diameter of the paper spool, and

is a little over one inch per hour. Care should be taken not to

allow this frame with its weighted pinion to fall. The paper may

be run off rapindly at any time by raising the pinion from the surface

of the paper, and gently drawing the paper downwards, or allowing

the lower cylinder to rewind it.

The brass bar under which the paper passes before it reaches

the front roller, is removeable, by unscrewing the wing nut which

forms its bearing on the right hand, and should be taken out when

inserting a new roll.

Examine the marking thread to see that it is properly on the

various pulleys provided for it, the pulley at the top of case with

a ratchet wheel on the same spindle is the driving pulley, the

motion being given by means of a wire click attached to the striking bar.

A few drops of Violet rubber type ink carefully placed on the

velvet covered pulley on the left side of the case, will keep the thread

inked for several months at a time. A drop or two of ink should

also be placed on the inking roller of the type wheel whenever the

marking of the hours becomes faint. Any excess of ink should be

absorbed with blotting paper.

The type wheel is lifted by a cam, and dropped every hour. It

can be turned to the correct time by the finger, but to set to exact

time the clock train must be spun round, holding the striking bar

outwards, until the correct spot on the paper is under the thread.

When set properly it will be found that the wheel drops about ten

minutes before each hour, stamping the next hour in advance. An

adjustable buffer spring is provided in order to keep the wheel from

resting on the paper, and smearing it with ink. The wheel lever

should never be forced down by the finger except just about the time

it has been dropped, otherwise the extension of the lifting cam may

be strained, and the adjustment put out of order.

The striking lever falls every minute, and provided an easy

method of timing the instrument, by checking its falls for a few

hours against the seconds hand of a good clock or watch. The

pendulum is regulated in the usual way, one turn of the screw

equalling about half minute per day.

The aneroid lever will be found tied up to keep it in place.

Remove the corks used to protect the needle points on the frame

carrying the boom rocks and place the points carefully in the cupped

jewels provided for that purpose.Attach the hooked link to the pin

on the right hand side of the frame, thus connecting the multiplying

lever to the boom. The boom ought to fall over to the left when

unconnected to the link, it being unbalanced slightly in this

direction, so as to be always pulling on the link.

A cord with a brass counterweight is now used to connect the

multiplying lever and the aneroid with the boom.

To prevent the cord slipping, one turn is given around the pin

provided for the purpose in the groove in the pulley. This

must be adjusted until the upper multiplying lever is

level, when the boom is vertical.

should the balance of the boom be at any time need to

be corrected, when freed from the cord, by adjusting

if necessary the end balance weights. When correctly adjusted

it should have scarcely any tendency to move away from any position

it may be put in. The balance weights should not interfere in

any way with the cord in the groove on the pulley.

A small lever has be

the lower paper drum for the

click from the wheel on the

not to move this lever exc

held; otherwise the weight

possibly do damage.

When about to

the handle should be

clip e

For the purpose

of adjusting the position of the boom on the paper, a sliding weight

is provided. This is actuated by a thumbscrew outside the case,

which by means of a cord draws the weight along the upper multiplying

lever. A movement of the sliding weight about half way along will

cause the boom to move the full width of the paper. Care must be

taken to slightly turn the nut in the reverse direction when

adjustment is complete in order to free the cones from contact with

the sliding weight.

The two dry cells operating the pendulum are behind the paper

at the back of the case.

The weight for the rewinding spool requires rewinding once

every four or five days.

As adjusted the range of the instrument is about half an inch

for the full width of the paper, three inches being equal to one

tenth, a magnification of 30 times.

Should the movements of the instrument appear sluggish at any

time, carefully examine the link joining the two multiplying levers on

the left It should be quite free from contact with the sides of the

levers only resting on the knife edges in the slots provided.

The shoulders of the knife edge bearing of the upper lever

should be quite clear of the supporting pillars, also the link from

the cell to the lower lever should not touch at the sides.

The front of the case may be completely removed at any time

by unscrewing the brass screws at the sides which are holding the

centre bar on which the doors are hinged.

The amplitude of the pendulum arc is determined by the position

of the contact springs relative to the toggle ( the little steel

finger hanging from the impulse plane) and this arc must always

sufficient to safely carry the click wheel well round for the wire

backstop click to fall into each tooth properly. A short arc will

result in a more or less rapid loss in time, according to the

frequency with which the back stop fails to catch up, and hold the wheel.

The arc can be increased in two ways, by moving the ebonite

block, which is slotted to allow of adjustment, towards the front;

or by slightly bending the springs upwards, taking care that the

under spring does not remain in contact with the higher one.