Frequently Asked Questions
Q1. What does a barometer do?
Q2. How do I set my aneroid Barometer?
Q3. How do I compensate my barometer for my altitude?
Q4. Should I tap my Barometer?
Q5. How do I convert inches to millibars.
Q6. Should a barometer hang on an outside wall?
Q7. What is the brass coloured hand for?
Q8. My barometer points to fair but it is raining what is wrong?
Q9. Does my barometer need servicing?
Q10 Can I screw the adjuster at the base of my stick barometer to make it read correctly?
Q11 I have heard that I can use a magnet to make the mercury in my barometer join together, is this true?
Q12 My barograph nib now makes a broad line and/or smudges the paper, what can I do to get it working properly?
Q13 How can I make a barometer?
Q14 When do I change the battery in my barometer?
Q15 How do I clean the dial of my barometer?
Q16 How can I send a barometer to you for repair?
Q17 Is a mercury barometer more accurate than an aneroid?
Q18. What is an Otheometer?
Q19. How do I find my altitude?
Q20 I have heard mercury will be banned soon?
Q21 What is air pressure all about?
A. A barometer measures the weight of air above it at any time. As this weight (or pressure) varies then we can often foretell the future days weather, the barometer does not forecast, it is the person that uses the barometer that makes the forecast.
A. Once decided where to position your barometer, the screw at the back of the barometer (sometimes visible through a small hole) should be turned left or right to adjust the black indicating hand to read the correct sea level reading. So, the idea being, everybody with an aneroid barometer reads this at sea level reading regardless of the altitude at which they are living. (For barographs adjustment of the knurled screw often near the top of the mechanism will move the pen arm up and down to reach the required reading.) Weather forecasters often give the air pressure during forecasts particularly during settled weather which is the best time to set a barometer. Alternatively, you can get the correct reading from a Met office or Weather station or a known good barometer. In the UK you can enter your postcode at the following link and get the reading nearest to you, beware not to rely on this during times of changing pressure as the data may not be updated more than once or twice a day. www.bbc.co.uk/weather Some barometers read in inches of mercury, others in millibars or Hectar Pascals, some in millimeters. Once set, your barometer should not need resetting unless you move although you may wish to check it every year or two.
A. With aneroid barometers once set there should be no need to correct for altitude as you should then always be reading your barometer as if it was at sea level. With Stick barometers it may be necessary to add an amount for altitude. The figures are available in tables but for general domestic use the old calculation of adding 1/10 of an inch for every 100 feet above sea level is usually quite accurate enough. We do print a small booklet on how to read the barometer from 1830's which we have added the more accurate compensation tables if required (currently available at £1.50 inc P & P in U.K.)
A. Any dial barometer aneroid or mercury will always have some amount of 'sticktion' therefore a GENTLE tap is normal.
(Tapping actually helps the user as it indicates which way the barometer is moving at the time it is being looked at.)
A. To convert inches to millibars multiply by 33.86
To convert millibars to inches multiply by 0.02953
Q6. Should a barometer hang on an outside wall?
A. It makes no difference to the pressure reading which wall you hang a barometer on. There may be a slight difference in temperature but not pressure. The pressure is the same inside as well as outside.
Q7. What is the brass coloured hand for?
A. You normally adjust the brass hand so that it lines up with the blue(black hand), you do this once a day usually in the morning and than you can tell which way the pressure is moving and by how much in 24 hours.It is more important to know the amount and direction of change than the actual pressure to predict the weather.
Q8. My barometer points to fair but it is raining what is wrong?
A. A barometer measures air pressure and as such the words should be ignored. It is more important to see which way the pressure is moving, this will indicate the approaching weather more than the words. Admiral Fitzroy coined a useful phrase which is as good today as it was then.
"Long foretold - Long Last
Short notice - Soon Past"
Q9.Does my barometer need servicing?
Most aneroid (non-mercury type) barometers do not require a regular service. A good aneroid will maintain reasonable accuracy for many years. Antique aneroid barometers have generally suffered from old age and often benefit from checking in the pressure chamber and will often need correction for differences in the diaphragm movement. There is, over many years, a tendency for the aneroid to loose some movement and become less sensitive, for this reason a check and clean of the movement may be advisable perhaps between 25 and 50 years. Mercury barometers similarly will often last many years most times getting damaged when moved. If all is working well then they can be best left alone until they stop functioning or become 'sticky' in their movement. Should you decide for us to overhaul any barometer we request you DO NOT send until we have seen pictures and discussed method of transport with you FIRST.
Q10 Can I screw the adjuster at the base of my stick barometer to make it read correctly?
If you have a fortin barometer, which is a metal tube with a glass reservoir at the base and scale at the top it will be designed to adjust the level of the mercury in the lower reservoir to the fuducial point which is a small ivory point. This means that the reading will then be more accurate as it is actually reading the true height of the mercury column. The divisions on the scale will be precisely engraved as will the vernier. Many people understandably confuse the adjusting screw,(more correctly called the transporting screw) at the base of wood cased domestic barometers for the screw they may have heard of or seen many years previous at school - college - university - work etc. It is not for altering the level of mercury (except in a few special types with level indictors on) but for restricting the movement of the mercury in the reservoir and tube by reducing the volume. It lifts up the leather base in the reservoir to do this, whilst it will appear to raise the level of mercury and thereby 'correct' the barometer to read as if it was at sea level it will restrict the mercury from being able to fall when the pressure falls and only work when the pressure increases. Generally this transport screw should be unscrewed so as not to interfere with mercury level. On a few occasions it may be possible to support the leather and make very minor adjustments to the level but this is coincidental and not the normal procedure.
This is a common misunderstanding, perhaps confusing the magnet used on a minimum and maximum thermometer to re-set the small steel level indictors. Mercury is non magnetic and will not join together what is probably an air gap. To rectify this problem it will need to be taken to a suitably skilled barometer specialist. It should not be sent or posted!
Barographs of the traditional type use a wet ink style nib. You should put a drop or two into the bucket of the nib and it should write reasonably thick even line. If it does not then you should check the following. Is the paper the correct type? it must be a special grade of paper that will not soak up the ink but will absorb a small amount of it. (Photo copies will not do) You should also have the correct ink for the paper and there are different types of recording inks. The pen should be in good condition, it may need cleaning carefully but if very old and corroded may need replacing. Our paper and ink work well together. We can not guarantee our ink on other paper or paper with our ink. It is normal to add a drop or two of ink every 2 or 3 weeks, if you are putting more than 2 drops a week in then something is probably not right! Nibs can be adjusted by altering the gap between the points carefully , they should be of even length and the wider apart they are the fatter the line is drawn.
Q13 How can I make a barometer?
Occasionally we are asked how to make a barometer. We make many types and believe me it is not that easy. Most people have a set type in mind, often a mercurial stick. Our services do not extend to assisting for the many hours necessary to teach someone to make their own barometer but if you have an idea about which type of barometer you may wish to make then send a picture or sketch and we can estimate the parts that may be needed to make such a piece. The barometers we make need special parts making which we often do to suit the individual barometer we are making,(that is why most of ours cost so much! they can take more than 100 hours of skilled labour to complete and many hundreds of pounds of parts.)
The simplist form of stick barometer will be one with a glass tube and this can be positioned along side a scale to read the pressure, the decorative case can be as simple or elaborate as is liked. Our own designs are normally based on antique models.
Q14 When do I change the battery in my barometer?
So far as we know only electronic types have batteries, these will need changing when they no longer work. The usual aneroid or mercury barometer does not have a battery so will not need changing.
Q15 How do I clean the dial of my barometer?
Most dials on antique barometers will be silvered brass and can not normally be cleaned at home. This really is a job for the specialist restorer. Other dials such as glass, card and ceramic need special care later barometers from about 1920's have aluminium dials which can not be cleaned.
Q16 How can I send a barometer to you for repair?
There are many different types of barometers, We request that you DO NOT send us any item before first contacting us preferably with a picture of the barometer. We can then advise if a repair may be possible, likely cost and how best to send or arrange for sending the item to us. Remember to include your address and other details.
Q17 Is a mercury barometer more accurate than an aneroid?
Well it will depend on just what they are both like. You could ask a similar question about cars, is a petrol car better than a diesel car? The answer in both cases is that it will greatly depend on how well made they both are and what condition they are in. Aneroid barometers generally are similar in accuracy to mercury barometers, both do have some small errors even if made well. There are accurate aneroid barometers and accurate mercury stick barometers which will normally be Fortin or Kew pattern ones - built for scientific accuracy not looks!
Well Robert Hooke made an Otheometer but no drawings survive. It worked opposite to a barometer and the root of the word is derived from othe = to push so it is some type of push meter. probably a type of weather glass. With our fascination in barometers we have re-designed this instrument based on Mr Collins experience and knowledge of old barometers and weather glasses. We are pleased to offer our own 'Hooke's Otheometer' for sale with accurately engraved style of paper charts and special patented tube which as Robert Hooke's Otheometer, moves down for low pressure and up for higher pressures. please contact us for details if you wish to have a truely unusal barometer!
Q19. How do I find my altitude?
Try looking on an ordnance survey map - the contour lines are at set altitudes and with a good pair of eyes you should be able to work out your altitude within a few meters. Knowing your altitude is not necessary for setting a barometer. Provided you are not over 1000 feet then most will adjust easily, if higher than 1000 feet some adjustment may be needed in a workshop and so the altitude where the barometer will be is needed.
Q20 I have heard mercury will be banned soon?
The E U have agreed a ban on the sale of New Mercury Measuring instruments including New Barometers. This will come into force in October 2009. The sale of second hand and antique barometers as well as their repair has not and is not in any way threatened at the moment. Dispite the fact that we make a few barometers and our glass blower makes tubes for repairs as well as new ones in future we will only be able to offer tubes fro restoration. Of course if we sell a tube we do not know what it will be used for and as it does not have a scale on it it will not be a barometer - an interesting question. We may well b eable to sell a barometer case without a mercury tube in it as well.
The ban is in order to stop tons of mercury that pollutes the world especially Europe, the likley fact is that the UK manufacture of new domestic stick barometers accounts for less than 20 kilos of mercury per year - little which is likely to get into the food chain or be wasted - beggars the question as to how the tons of mercury currently entering into the food chain is getting there! certainly not by barometers!
The UK burns coal in its power industry (we import 491 Million Tons per year!) and it is reported that the small amount of trace mercury sometimes found in coal is polluting the atmosphere with mercury vapours which turn to methyl mercury and settles and pollutes Europe. For many decades the UK and other countries have been using mercury amalgam fillings, and excellent they are as well. But what happens to the fillings when they get cremated? - into the atmosphere with the smoke! how many cremations a year do we have in the UK alone?
Florecent lights have a small amount of mercury in them, any chance of banning them - NO! (I asked the EU and they think there is no alternative so no ban in sight) what if the light manufacturers were taxed 1 euro for every bulb made? that would produce funds to help tackle the mercury waste problem. Where do old flourecent light bulbs end up? well the regulations state that they should not be sent to land fill (mercury might leak out of them) so where do you send them? well if you are really dedicated to saving the enviroment you search around until you find a special bank to collect them (at a cost) or like us you arrange collection and they end up with Mercury Recycling in Manchester (tel 0161 877 0977) who correctly re-cycle them and extract the mercury. Where does your company or council get rid of its flourecent light bulbs? chances are normal waste! where do you dispose of yours?
But never mind EU are banning the faithfull domestic barometers so all will be well with the plant earth and mercury pollution will be a thing of the past! Dream on European masters.
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