If you always wanted a mercury barometer in your house, but don't want to deal with the hazardous material aspects of mercury, this may be an alternative.  The Eco-celli E038 is a sympiesometer, more commonly called a tendency barometer today.  It was manufactured by Dingens in Belgium.  A tendency barometer uses Boyle's Law, which was discovered in 1662.  It states that, for a fixed mass of an ideal gas at constant temperature, the volume is inversely proportional to the pressure.  In this barometer, the fixed mass of gas is above the red fluid in the glass tube on the upper left of the device.  The glass tube is U-shaped, and the other leg of the tube is open to atmospheric pressure.  As the atmospheric pressure varies, the volume of the fixed mass changes resulting in a varying fluid level in the open leg.  The clever thing about this barometer is that it has a sliding pressure scale that is adjusted based on the temperature. The blue fluid in the large thermometer on the right of the instrument measures the temperature, and the sliding pressure scale is moved until a pointer is at the temperature fluid level.  This results in an atmospheric pressure value without doing any manual temperature adjustment calculations.

Some of the key features of of the Eco-celli barometer include:​

• The built-in calibration only works for measurement of sea level pressure.  It can't be used to measure local pressure at altitude.  On the other hand, no adjustment calculations to a sea level value are required.  If you want the local pressure value, you need to do the inverse calculation to the sea level pressure adjustment calculation as performed for a mercury barometer.
• Unlike a mercury barometer, it has a 'Contra' pressure scale, that is the atmospheric pressure value increases as the fluid level in the barometer goes down.
• It comes from the manufacturer calibrated for use at sea level elevation.  In order to use it at your local elevation above sea level, you need to withdraw some of the red fluid from the barometer tube until the fluid level reads your correct sea level pressure.  A plastic syringe and flexible plastic tubing is supplied to accomplish this.
• The pressure scale is in inches Hg and mm Hg.  The mm Hg scale has better resolution.  It's a school barometer, not an observatory barometer.
• Overall it's about 38.5 inches tall and 5 inches wide.  The frame is clear plastic, the tubes are glass.  Minor assembly is required, no tools needed.
• It's attractive and colorful with its red and blue fluids.  A sure science conversation piece for your home.

In the USA, the Eco-celli can be purchased from Allivan Barometers.  In other parts of the world it's available directly from Dingens.

​The instructions for the Eco-celli barometer can be downloaded below (4 pages):

Instructions for adding red fluid to the Ecco-celli barometer barometer may be downloaded below (1 page):

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