Maker

Thommen, Switzerland

Model

Type 2A2

Serial Number

25294

Dimensions

110 x 115 x 125 mm

Image

Description

Precision aneroid barometer with dial readout (two hands). Range 500 to 1100 mbar (hPa). Outer scale (long hand) 0-100 hPa, inner scale (short hand) 500 - 1100 hpa. Least count 1 hPa, estimate to 0.1 hPa.

Below the long hand is a chromed (mirror) ring that allows to avoid parallax when reading the pressure. (Move the eye until the reflectio of the hand is covered by the hand (which is then directly above the reflection).

Two bimetallic arrangements serve to compensate the effects of temperature on the measuring elements between -25 degrees and +35 degrees Celsius. The device includes high grade evacuated aneroid capsules and features a zero point adjustment.

Weight without case 0.61 kg, with case 1.65 kg.

'Indicating' accuracy: ±0.1%

Scale length: 1200 mm (6 revolutions)

Spot bubble in bottom left corner of top of case.

Instrumnet is designed for measuring absolute pressure and vacuum up to 5000 m altitude.

Reproducebility: 0.03%

Response sensititity: 0.01%

Hysteresis: < 0.1%

Users are advised to set up the barometer on a horizontal surface and to gently tap the barometer before reading to release any friction in the mechanism (reduces hysteresis).

History & comments

Ca 1970s. Used for barometric heighting and for pressure measurements during (precision) electronic distance measurements.

Conservation

in steel case which shows some rust

Condition

actual barometer in excellent condition, carrying handle of case missing

Remarks

Marked "P.C. 42470" and "S/N 25294"

Dates

Catalogued by JMR in 2012. Photo by JMR.