What is "sympiesometer"

Sympiesometer \Sym`pi*e*som"e*ter\, n. [Gr. ? compression (fr. ? to press together; sy`n with + ? to press, squeeze) + -meter.] A sensitive kind of barometer, in which the pressure of the atmosphere, acting upon a liquid, as oil, in the lower portion of the instrument, compresses an elastic gas in the upper part.

Note: The column of oil of a lower part BC of a glass tube compresses hydrogen gas in the upper part AB, and is thus measured on the scale pq by the position of a surface of the oil in the tube. The scale pq is adjustable, and its index must be set to the division on the scale rs corresponding to the temperature indicated by the termometer t, in order to correct for the effects of temperature on the gas. It is sensitive, and convenient for use at sea, but inferior in accuracy to the mercurial barometer.

n. A sensitive kind of barometer, in which the pressure of the atmosphere, acting upon a liquid in the lower part of the instrument, compresses a gas in the upper part.

A sympiesometer is a compact and lightweight type of barometer that was widely used on ships in the 19th century.

The sympiesometer consists of two parts. One is a traditional mercury thermometer that is needed to calculate the expansion or contraction of the fluid in the barometer proper. The other is the barometer, consisting of a J-shaped tube open at the lower end and closed at the top, with small reservoirs at both ends of the tube. The lower end of the J and its associated reservoir were filled with colored almond oil, while the upper portion and its reservoir were filled with hydrogen gas. Increasing air pressure would cause the oil to be pushed out of the lower reservoir and into the tube, compressing the hydrogen gas into the upper reservoir. The pressure was indicated by the position of the top of the oil. To correct for temperature, a sliding scale was used; the operator would first use the thermometer to set the scale and then measure the pressure from it.

The basic idea is similar to the common weather glass that had been in use for some time, but the use of highly compressible hydrogen in a long, thin tube allowed much more accurate measurements, as changes in pressure resulted in much more movement of the liquid. The basic concept was initially demonstrated by Robert Hooke, which he referred to as the Otheometer. However it remained unused until it was re-introduced by Alexander Adie.

Category:Pressure gauges Category:Meteorological instrumentation and equipment