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Barometer World Ltd, Quicksilver Barn, Merton, Okehampton, Devon EX20 3DS   Click here to contact us.
01805 603443
01805 603443

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 How can I get my barograph drawing a line 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?
Q22 What size barograph paper do I require?
Q23 What books has Philip Collins written about Barometers?
Q24 How do I change the chart on my Barograph?
Q25 How do I check the wild oat Hygrometer?
Q26 How do I set a Barograph?
Q27 How do you set a Mercury Wheel Barometer?
Q28 Why are barometers seldom used outside?

Q1 What does a Barometer do? [top]
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.

Q2 How do I set my aneroid Barometer? [top]
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. 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.

Q3 How do I compensate my barometer for my altitude? [top]
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.)

Q4 Should I tap my Barometer? [top]
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.)

Q5 How do I convert inches to millibars. [top]
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? [top]
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? [top]
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? [top]
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? [top]
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? [top]
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.

Q11 I have heard that I can use a magnet to make the mercury in my barometer join together, is this true? [top]
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!

Q12 How can I get my barograph drawing a line properly? [top]
Barographs of the traditional type use a wet ink bucket style nib. You should put a drop or two into the bucket of the nib and it should write reasonably 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. It is common with new nibs or nibs that have not been used for some time to be dry on the ends and even with ink in them they will not draw a line. This is because the nib works by capillary action (like a fountain pen) It may often be necessary to start a new or very dry nib by using a small needle or pin etc to put ink on the paper, once started the nib will continue to draw a line until the ink is exhausted. Then a drop more will work easily. Blotching of ink is often a sign of incorect or not matching paper and ink. Our director Philip Collins wrote a useful book about barographs a few years ago which will assist many poeple in understanding the types of barographs, ages etc, and has a bit about general use and care, the book, as well as charts, ink and nibs can be bought online direct from us at BAROGRAPH PARTS

Q13 How can I make a barometer? [top]
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? [top]
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? [top]
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? [top]
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? [top]
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!

Q18. What is an Otheometer? [top]
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 unusual barometer!

Q19. How do I find my altitude? [top]
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 Is mercury banned? [top]
The E U have agreed a ban on the sale of New Mercury Measuring instruments including New Barometers. This came 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 for 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 be able 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 likeley fact is that the UK manufacture of new domestic stick barometers accounts for less than 20 kilos of mercury per year - little of which is likely to get into the food chain or be wasted - begs 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.

watch our NEWS section of this website for more recent updates as they occur.

Q21 What is air pressure? [top]

Q22 What size barograph paper do I require? [top]
We are often asked what charts suit someones barograph, and to be honest it is very difficult to know over the phone. Regrettably we do not know all the models ever made, there were many variations. However many accept standard type charts. Our most common types is ref 1005750 which is 300mm long and 90mm high in millibars, we also have ref 1005775 which is a MET office style chart which measures 306mm by 90mm high both measure vertically 950 to 1050 millibars. To get the best fit chart we always suggest to start from the beginning. Often charts that are being used are not the original ones anyway but came with the barograph or were only ones available at the time. So measure the circumference of the drum by wrapping a piece of paper around the drum and marking were the two ends overlap, add about 5mm to this measurement and this is approx the length of chart required, it can be a little longer but hardly any shorter. Then measure the height of the drum, a chart should not exceed the height of the drum and often can be 1 or 2mm shorter. Our standard charts are available to be seen and ordered at Many different types were made over last 125 years, on occasions we can arrange special reprinting of charts to suit a more unusual item but quantities often need to be 1000 to defray cost of set up of printing machine and artwork preparation. If best time keeping is required then this will need to be checked by starting the barograph and marking the beginning of a chart after an hour or so (to allow the clockwork gears to catch up any slack) after exactly 7 full days (168 hours) mark the chart again and measure the length - seldom does anyone ask for such accuracy but it gives a guide as to the length of printing required for 7 full days. Barograph makers years ago supplied many similar barographs but with slightly different time speeds. Also to check is the range of the barograph, this is harder and our own manufacturing and restoration involves testing in a pressure chamber and calibrating the barograph accordingly. However most old barographs of common size will generally measure 3 inches of mercury from 28 to 31 vertically (on a curved graph) millibars equivalent is 950 to 1050 usually. Another couple of factors to consider is the measurements required in terms of pressure readings, we sell millibar charts as well as inch measuring charts which is rather old fashioned these days, the weather reports use millibars on TV and Radio. The 2nd consideration is whether the charts you require are held on with a clip of some type of if no clip then need to be adhesive. We sell both adhesive and non adhesive, the adhesive ones are more expensive and unnecessary if your barograph has a clip system to secure the charts in position. Most of our charts are also printed in old fashioned colours as many old charts were, green, orange or red charts, we think they look better than boring old grey. We probably supply 75% of the standard type of charts and certainly without the actual item to undertake the above checks we would be unable to be certain which might suit best. If you have a different size drum than the charts we have then e-mail us a picture of the barograph with the lid (or cover) open so we can see the design etc. It may be possible to use something close or we may be able to supply blank paper for you to print your own small numbers of charts - the paper is a special type for the ink that is used. Hope that helps.

Q23 What books has Philip Collins written about Barometers?[top]

Q24 How do I change the chart on my Barograph?[top]

Q25 How do I check the wild oat Hygrometer[top]

Q26 How do you set a Barograph?[top]

Q27 How do you set a Mercury Wheel Barometer?[top]

Q28 Why are barometers seldom used outside? [top]
In actual fact a few barometers are used outside - such as those used for measuring altitude either above or below sea level for a variety of reasons such as water pressure supply, walking and climbing, reading maps, ordanance aiming and several other reasons. For weather prediction, the main use of a domestic barometer, then very few are used outside. There are some designed for public display such as rare ones on church towers or public buildings more for loccal interest than serious weather prediction. Famously Admiral FitzRoy placed some around the coast for publc use when barometers were more expensive and only the rich would own one. These days barometers are primarily used indoors because the pressure inside the house is the same as outside the house (unless you live in a totally sealed envirment - which is rare indeed). However if you want to know the pressure to attempt to predict the weather then a nice decorative barometer fares better in the more aimable climate of a house than outside.