Electrical control mercury monometer

A mercury manometer indicating a differential pressure and for providing a closed electrical circuit at preselected pressure readings comprising:

• (a) a body formed from a block of electrically nonconductive material, said body having formed in its front surface
• (i) a mercury well having a first channel communicating with a pressure input connection,
• (ii) an essentially rectangular mercury column channel having an upper pressure outlet connection, said channel formed by a broad, flat rear face and a pair of narrow side walls,
• (iii) a second channel communicating between said well and said mercury column channel,
• (iv) a continuous O-ring groove bounding said mercury well, said first channel, said mercury column channel, and said second channel, and
• (v) a plurality of conductive contacts embedded in a vertical array in said rear face of said mercury column channel forming said electrical control contacts, said contacts extending through said block to form rear external electrical connections;
• (b) an O-ring gasket formed from resilient material and disposed in said O-ring groove;
• (c) a transparent face plate attached to said front surface of said body block and adapted to compress said O-ring gasket to form a pressure tight seal between said face plate and said mercury well, said first channel, said mercury column channel, and said second channel thereby forming a mercury well for holding mercury and said vertical mercury column;
• and
• (d) mercury disposed in said well and said column, whereby pressure applied to said pressure input connection causes said mercury column to rise and sequentially form electrical connections between said common contact and others of said plurality of electrical control contacts.