1) Remove the plastic cover on the back of the Barometer by peeling it up and away.

2) Remove the back cover on the back of the Barometer by gradually and carefully pulling it away from the perimeter. The back is held on by four adhesive pads. If it doesn’t feel like it wants to release, use a hair dryer to slightly warm up the edges of the back, and it should be removed easily.

3) After removing the back cover, you will see the barometer movement. DO NOT DISTURB THE BLACK RUBBER MEMBRANE. There will be a brass flat head screw in the middle of the movement.

a) Set the brass reference needle on the front to your current barometric pressure in your area by turning the finger screw on the front of the clock.

b) Using a small, flathead screwdriver, turn the brass screw on the movement in the back until the two needles align. (one above the other). Do not press hard on the screw while turning it.

c) After about 30 minutes, check the current barometric pressure in your area and if it has not changed, adjust the screw again if it has drifted from the reference needle.

Your barometer should now be adjusted.

Notes: Usually, the pressure inside will not vary as much as the outdoors because of fan blowers and HVAC systems. When you open your outside door, you will feel air escaping to the outside as the pressure is usually higher inside than outside.

How it works:

A barometer with a needle connected by mechanical linkages and springs to a thin, hollow metal disk in which a partial vacuum is maintained: a change in atmospheric pressure changes the shape of the disk, thus moving the needle.The normal, average sea-level pressure is about 29.91 inches or 1013 mB, which means the barometer’s needle will rest near 30 or between 1012mB and 1014mB. Pressures seldom increase or decrease 1 inch above or below the 30-inch mark unless weather conditions are extreme.

Generally, low or decreasing barometric pressure means cloudy, unsettled or wet weather, and high pressure or increasing pressure means calm and clear weather.Changes in pressure are more important than exact readings – a downward trend is a general predictor of stormy weather, and an upward trend suggests fair weather.

Millibars to Inches Conversion Table for Hermle Barometers

Millibars	Inches	Millibars	Inches	Millibars	Inches	Millibars	Inches
1050	31.01	1011	29.85	972	28.70	933	27.55
1049	30.98	1010	29.83	971	28.67	932	27.52
1048	30.95	1009	29.80	970	28.64	931	27.49
1047	30.92	1008	29.77	969	28.61	930	27.46
1046	30.89	1007	29.74	968	28.59	929	27.43
1045	30.86	1006	29.71	967	28.56	928	27.40
1044	30.83	1005	29.68	966	28.53	927	27.37
1043	30.80	1004	29.65	965	28.50	926	27.34
1042	30.77	1003	29.62	964	28.47	925	27.32
1041	30.74	1002	29.59	963	28.44	924	27.29
1040	30.71	1001	29.56	962	28.41	923	27.26
1039	30.68	1000	29.53	961	28.38	922	27.23
1038	30.65	999	29.50	960	28.35	921	27.20
1037	30.62	998	29.47	959	28.32	920	27.17
1036	30.59	997	29.44	958	28.29	919	27.14
1035	30.56	996	29.41	957	28.26	918	27.11
1034	30.53	995	29.38	956	28.23	917	27.08
1033	30.50	994	29.35	955	28.20	916	27.05
1032	30.47	993	29.32	954	28.17	915	27.02
1031	30.45	992	29.29	953	28.14	914	26.99
1030	30.42	991	29.26	952	28.11	913	26.96
1029	30.39	990	29.23	951	28.08	912	26.93
1028	30.36	989	29.21	950	28.05	911	26.90
1027	30.33	988	29.18	949	28.02	910	26.87
1026	30.30	987	29.15	948	27.99	909	26.84
1025	30.27	986	29.12	947	27.96	908	26.81
1024	30.24	985	29.09	946	27.94	907	26.78
1023	30.21	984	29.06	945	27.91	906	26.75
1022	30.18	983	29.03	944	27.88	905	26.72
1021	30.15	982	29.00	943	27.85	904	26.70
1020	30.12	981	28.97	942	27.82	903	26.67
1019	30.09	980	28.94	941	27.79	902	26.64
1018	30.06	979	28.91	940	27.76	901	26.61
1017	30.03	978	28.88	939	27.73	900	26.58
1016	30.00	977	28.85	938	27.70
1015	29.97	976	28.82	937	27.67
1014	29.94	975	28.79	936	27.64
1013	29.91	974	28.76	935	27.61
1012	29.88	973	28.73	934	27.58