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Phone: (828) 698-1952 Toll Free: (877) 210-2344
Ross Tendency Barometer
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OUT OF STOCK
The Ross Tendency Barometer is mounted in an exquisitely crafted wood and curved glass case. A tribute to the famous Artic and Antarctic explorer James Clark Ross (1800 -1862) discoverer of the magnetic North Pole. His ship, the Erebus, is pictured at the top of the instrument and a map of the Antarctic is pictured below.
The Tendency Barometer was patented on December 23, 1818 by Alexander Adie. It was used by Ross on his expeditions. He is quoted in his diary as saying " the advantage of the tendency barometer to a mercury barometer is as big as having a mercury barometer to having no barometer at all." It consists of two liquid filled tubes. One tube in a U-shaped which is open ended and filled with a red fluid; and one closed thermometer tube filled with a blue fluid, mounted parallel to each other.
When the fluid levels are the same, the weather is changing.
When the red fluid level is below the blue fluid level, the weather is fair (high pressure pushes the red fluid down in the tube).
When the red fluid level is above the blue , stormy weather is predicted (low pressure allows the red fluid to move up the tube).
The thermometer measures in both Celsius and Fahrenheit and the barometer measures in millibars/ hPa. The overall instrument measures 20 inches high by 6.7 inches wide and weighs 3 pounds. An absolutely beautiful presentation piece that will last for generations.
Contents of Box
In the box you will find:
Tendency Barometer consisting of:
Barometer U-shaped tube with red fluid
Thermometer tube filled with blue fluid
Tendency Dial – tracks pressure changes
Hygrometer – measures relative humidity
The User Manual below on this page.
Calibration Kit with syringe and plastic tubing.
Note: Be sure to remove the rubber tube and rubber plug from the top of the barometer tube. These are only present during shipping to prevent spillage of the red fluid.
User Manual
On December 23, 1818, Alexander Adie, an optician from Edinburgh, received his patent for an invention: the Sympiesometer . He named his invention using the Greek words “sumpiesometer” (pressing together) and “metron” (measure). His instrument proved to be a reliable weather predictor. We constructed, according to his patent, a completely new series of very special weather instruments: The Tendency Barometer
A Tendency Barometer consists mainly of two parts: A U-shaped tube (red fluid) and a thermometer (blue fluid). The red fluid rises or falls according to changes in air pressure. The U-shaped tube is also influenced by temperature, that is the reason why the combination with the thermometer is required. All temperature deviations during the reading of the pressure tendency will be corrected. All you need to do is to compare the level of the red fluid to the blue fluid. The difference between both fluid levels (use the Celsius scale to take difference readings) is set with the pointer on the Meteo-tendency scale. The changes in air pressure can be easily observed and an accurate forecast made.
Example : When the red fluid is 6 lines below the blue fluid. -6 (remember, use the Celsius scale to take the difference) the weather forecast is for Fair Weather. When the red fluid is 8 lines above the blue, +8, the forecast is Rainy or Stormy.
When the red and blue fluid levels are equal , the weather condition is Change .
Red fluid below the blue fluid, Good Weather (high pressure).
Red fluid above the blue fluid, Bad Weather (low pressure)
You can also take actual pressure readings in hPa, which is the equivalent to millibars. The pressure level in millibars is printed around the Meteo-tendency dial.
The Hygrometer is used to measure the degree of humidity in the air near this unit. The amount of humidity is measured by transferring the differences in length from a humidity sensitive material to a pointer on the scale. A hygrometer should be calibrated at least once per year. You can do this by soaking a towel with water. Put the hygrometer for at least 20 minutes on this towel. The hygrometer should now indicate 97-98%. If the hygrometer shows some other value, it can be set to 97% on the back of the hygrometer using a small screwdriver. Please do not use force when setting the hygrometer!
Barometer Calibration
As with all other barometers a tendency barometer has to be set for the local altitude if your location is more than about 150 feet above sea level. Check with your town or city hall for y
our altitude if you don’t know it.Calibration method:
To calibrate the apparatus, a calibration kit is included. You will need it now. Refer to the diagram as needed.
Put the needle stub onto the syringe if it is not already installed and remove the protective cover over the needle stub.
Carefully slide the thin plastic tube over the needle stub.
When the air pressure is 1013 millibars or 29.92 inches of mercury, remove as much fluid as needed to make both red and blue fluid level equal with each other. A difference of 1 dash on the Celsius scale between both fluid levels represents 0.16 inches of mercury pressure. (Note: You can find your local air pressure by watching TV such as The Weather Channel, or going onto the internet to www.weather.com or other such weather web sites.)
The tendency barometer is now calibrated
| Problem | Solution |
| Air bubble in the left hand red fluid | Use the thin plastic tube to prick through the air bubble |
| Air bubble in the right hand red fluid | Put the instrument upright in the refrigerator for approx. 1 hour. The air bubble will disappear. Or, attach the rubber tube and rubber plug to the end of the open barometer tube. Squeeze the rubber tube until the gaps are gone, then remove the rubber tube and plug. |
| Barometer not working properly | You are at a higher altitude than the one the instrument is calibrated for. Calibrate the instrument using the above calibration method. |
| Hygrometer not working properly | Calibrate the hygrometer. (see hygrometer section) |
| In case of glass breakage. | Try to collect the colored fluid and all pieces of glass in a container. The red fluid consists of red pigment in oil, the blue fluid is alcohol. If the red fluid is spilled, remove it with paper towels. Rinse the stained places Immediately with soap and water. |
| Air bubble in blue thermometer fluid | Heat the thermometer tube carefully using a hair dryer on low setting |