A barometer is a scientific instrument used in meteorology to measure atmospheric pressure. Pressure tendency can forecast short-term changes in the weather. Many measurements of air pressure are used within surface weather analysis to help find surface troughs, high-pressure systems and frontal boundaries.FEATURES:Bimetal element provides temperature compensation for aneroid capsuleNeeds no batteries or external powerChoose from mbar/mm Hg or mbar/inches Hg modelsIncludes an attractive brass case and include a bezel for easy bulk-head mountingUse these economical instruments for long-term temperature, relative humidity and barometric pressure monitoringAneroid BarometerSPECIFICATION:Triple Scale Aneroid Barometer is made of solid brass & stainless steel construction, which keeps it durable for years of classroom use. Measuring 6 in diameter it is wall mountable, calibrate able and is also RoHS compliant. The range of the meter is 27.75 ? 31.25 in Hg, 70.5 ? 79.4 cm Hg, 940 ? 1080 m bar and the accuracy of the meter is ?0.1 in Hg, ?0.3 cm Hg, ?3.5 m bar.