A barometer displays the present pressure and the change of pressure since it was last set using a marker hand on the dial.
A barograph records the history of the pressure on a paper chart, wrapped around a clock-driven drum.
Underway on a fully crewed vessel, the logbook serves as a detailed record of pressure changes.
On overnight anchorages, a printed barograph trace is a convenient way to learn how the pressure changed during the night when there was no watch to record it.
It uses a set of 7 aneroid capsules with a diameter of 62 mm made from copper-beryllium alloy. This material essentially eliminates age-hardening, hysteresis, and elastic after effects that could otherwise degrade the accuracy.
The influence of temperature on the set of aneroid capsules and the transmission system is compensated by use of bi metal components over the full measuring range and for temperatures between -30 to +40 °C (-22 to 104 °F).
All contacts in the movements are jeweled to reduce friction.
Measuring range used for altitude 955 to 1055 hPa 930 to 1030 hPa 905 to 1005 hPa 880 to 980 hPa 855 to 955 hPa 0 to 150 m above sea level 150 to 350 m above sea level 350 to 600 m above sea level 600 to 850 m above sea level 850 to 1,100 m above sea level
Electronic quartz clockwork
Can be shifted to take daily weekly or monthly measurements
Revolution times changeable: daily revolution 25.6 h, weekly revolution 176 h, monthly revolution 783 h
Autonomous operation 12 month with battery type LR6 autonomous operation 1 week
Note that the mechanical clocks do not have a monthly mode.
Weekly rotations are the most common used with barographs
The recording instruments are delivered complete with fibre pens and a year's supply of recording charts.
Weekly charts are the standard that are provided unless requested otherwise.
Fischer instruments are unique in offering an option on each model with enhanced dampening for barograph use at sea.
After you chose your model and timing option, the extra dampening can be selected.
There is no need for this option for land based operations.
The paper charts are the same size for all models: 92mm tall by 302 mm long.
Charts marked in inches of mercury are also available on request.
All of our products come with a manufacturers warranty. We carefully selected these brands as they are high quality and seldom have issues. But if they ever do - you know you are covered by a warranty.