Casella CEL Barographs small and display pattern User Manual

Side 4

Ordering Information

When ordering from the list below, please quote catalogue reference numbers.
Small Pattern barograph complete with clock and 2 pens M110004

Small Pattern barograph complete with clock, 2 pens and

UKAS calibration certificate M110012
Display Pattern barograph complete with clock and 2 pens M110002
Display Pattern barograph complete with clock, 2 pens and

UKAS calibration certificate M110010

Accessories & Spares

Pack of 2 black ink pens M118004
Pack of 200 charts, range 28 - 31 inHg M107701
Pack of 200 charts, range 950 - 1050 mb M107702
Pack of 200 charts, range 710 - 790 mmHg M107703
Chart Clip CMA39
Clock CM414
Key CMA42
Mainspring CMA24
Escapement CMA16

BAROGRAPHS

User Instructions

7. SERVICING

CASELLA CELs in house service department offers a comprehensive range of repair and
calibration services, designed to effect a fast and efficient back-up for all our products. The Service
Department is operated under the scope of our BSI registration for products manufactured by us.
We will however, undertake the repair of other manufacturers equipment.

For further information please contact the Service Department at our Bedford premises. We will
be happy to provide quotations for individual repairs or provide annual maintenance under contract.

IMPORTANT:
For our U.K. customers, service under guarantee is offered only by the CASELLA CEL Ltd service
department at Regent House Kempston Bedford. There are no U.K. agents or repair service author-
ised by us to carryout this work. In order to ensure that only approved replacement parts are used
for routine maintenance, after the guarantee period, we recommend that this is carried out by our
fully skilled service engineers. In the case of service required outside the U.K. we recommend that
it be carried out by our appointed agents.

CASELLA CEL LIMITED
Regent House
Wolseley Road
Kempston
Bedford
MK42 7JY
Telephone: [phone]
Facsimile: [phone]
E-Mail: [e-mail]
Webpage: http://www.casella.co.uk

The contents of this handbook are subject to change without notice.

ALTERATION WITHOUT NOTICE

BAROGRAPHS
User Instructions

August 2000

BAROGRAPHS

SMALL PATTERN W2450/2

DISPLAY PATTERN T10558/2

User Instructions

HB3123-04

The copyright in this document which contains proprietary information is vested in CASELLA CEL LIMITED.

The contents of this document must not be used for purposes other than for which it has been supplied or

reproduced or disclosed wholly or in part without the prior written permission of

1. INTRODUCTION

The measurement of pressure and the rate of
change of pressure are important meteoro-
logical observations with regard to forecasting
weather conditions.

The recording of atmospheric pressure
changes enables meteorologists to make short
term local forecasts. The most convenient
method of studying the rate of change in

COPYRIGHT

CASELLA CEL LIMITED.

pressure is with the aid of a Barograph, which
records the pressure variations graphically
onto a revolving chart drum.

Two versions of the barograph are available:
the Small pattern and the Display pattern. Both
versions can be supplied complete with a
UKAS (formerly NAMAS) calibration certificate.

Side 2

BAROGRAPHS

User Instructions

BAROGRAPHS
User Instructions

Side 3

2. PRINCIPLE OF OPERATION

The barograph relies upon the aneroid principle
to measure atmospheric pressure. This
consists essentially of an evacuated metal
chamber with flexible metal walls.

As atmospheric pressure changes, the
changing pressure difference between the
inside and outside causes the chamber to
expand and contract. These movements are
magnified mechanically to move a pen across

3. SITE SELECTION

All barographs should be placed on a rigid
support to eliminate vibration. The installation
height should be convenient for observation
and chart changing.

When being used for weather forecasting,
synoptic work or any form of routine pressure

4. OPERATION

1. Remove any traces of packing material

before removing or hinging back the cover
of the barograph.

2. Remove the chart drum lid, and slide out

the chart clip.

3. Wrap a new chart around the drum, making

sure that the ends overlap and the bottom
of the chart just touches the flange of the
drum.

Make sure that the overlap lines are
carefully aligned.

4. Replace the chart clip.

5. The chart drum is removed by lifting off the

drum lid and unscrewing the knurled nut in-
side the drum.

6. The drum can then be lifted off the spindle.

7. Fit the chart as described above.

8. When replacing the chart drum onto the

spindle make sure that the gears mesh be-
fore replacing the knurled nut.

5. CALIBRATION

It should be noted that although the barograph
is factory calibrated, during transit it is possible
that the calibration settings may have altered.

a recording chart. The chart is wrapped around
a drum which rotates at one revolution per
week. The pressure trends are displayed with
a sensitivity of 1 mb = 0.75 mm.

To provide easy, trouble free writing, a fibre
tipped pen is supplied. This has enough black
ink in its body to write for many months. It
should be replaced when the trace becomes
faint.

measurement in industry or research, care
must be taken to select suitable surroundings.

Barograph instruments should not be
subjected to wide variations in ambient
temperature. Select a location remote from
radiators, sources of hot or cold air or direct
sources of sunlight during any part of the day.

9. Take one pen out of the sachet, leaving the
other pen sealed for future use.

10.Remove and discard the fibre pens protec-
tive cap.

Do not press

see how it writes, this will damage the
pens fine tip, and prevent ink flow.

11.Slide the pen onto pen arm. N.B. The raised
edges on back of pen block have an inner ta-
per to secure the pen to the arm.

12.Push the pen onto the pen arm until it
touches the raised spot.

13.The clock can now be fully wound by the
key under the lid and the latter replaced.

14.Rotate the clock drum such that the pen is
positioned to the correct time and day.

15.Rotate the pen lifter knob to release pen on
to chart.

All barographs record variations in pressure at
station elevation, however, for most purposes
the reported pressure readings represent the

the pen onto the chart, to

pressure corrected to mean sea level. All
barograph charts are printed with a scale for
sea level pressure ranges.

To display sea level pressure, the absolute
pressure must be known for the stations
elevation and the appropriate altitude-pressure
correction applied. The best method is to have
a mercury barometer at the station so that
comparison of the two instruments can be
made. Assuming a standard atmosphere, the
pressure at sea level will be approximately

0.12 mBar higher for every meter increase in
height.

The pen offset should be adjusted to indicate
the corrected sea level pressure. It is advisable
to spread this adjustment over a few days
gradually approaching the correct reading.

If a mercury barometer is unavailable a good
quality aneroid barometer which has been
recently checked can be used.

For less accurate readings ,e.g. home, club or
school, the following method may be
adequate. Telephone the nearest
meteorological station stating the exact
position of the barograph site. From this the
meteorological service can provide a pressure
reading usually to ± 0.5 mb. If there is a
meteorological observing station near the

barograph site then a closer reading maybe
available. In the United Kingdom, consult the
telephone directory for the nearest
meteorological station .

For setting the barometer offset, use the
adjustment knob located between the
chamber and the clock assembly. Turn
clockwise to raise the pen and anti-clockwise
to lower the pen.

The day to day readings are now automatically
reduced to sea level and corrected for altitude.

It is advisable to repeat the above mentioned
checks periodically in case the readings alter.
When finally all adjustments are made,
recording can begin, set the clock to the
correct time.

It is recommended that time marks should be
made on chart records to keep a check on the
time keeping accuracy of the clock. The first
mark should be not more than 2 hours after
starting and then subsequently one mark per
day. In all cases the time of the mark must be
noted in a register.

To make a time mark lift off the case and
depress the pen arm a small amount.

If the barograph is only used for general
interest then time marks are not necessary.

6. MAINTENANCE

In a dusty atmosphere brush off any dust from
the pivots.

The clock spring should not require any
attention for approximately 2-4 years and does
not need cleaning if it keeps good consistent
time, never stops unaccountably and has a
normal sounding regular tick. If the timing
should need altering, the regulator is under a
small plate near the winding key. A competent

clock repairer can clean and regulate the clock
when necessary.

When the clock is sent away for cleaning or
repairing, the spindle and clock base should be
sent with the clock.
spindle from the base.

Note:

cleaning or general servicing of the instrument.

The warranty does not extend to

Do not

remove the

8. TECHNICAL INFORMATION

Specification

Ranges covered: 950 to 1050 mb, 710 to 790 mmHg, 28 to 31 inHg
Pen travel: 75 mm
Sensitivity: 1 mb = 0.75 mm, 1 mmHg = 1.0 mm, 1 inHg = 25.4 mm
Accuracy: ±1 mb
Time scale: 1.66 mm/h, 172 hours total
Clock: Weekly, spring drive
Dimensions: Small Pattern: 310 x 160 x 190 mm, 3.85 kg

Display Pattern 370 x 230 x 210 mm, 5.6 kg