Inclined Limb Manometer
This is another variation where the construction is based on a glass reservoir connected via its base to the glass tube which is set at an angle rising to the maximum level which can be in the cistern. Again it is basically a differential pressure measurement instrument.
Whilst use is diminishing today, it is still used in low pressure applications, usually about 20 inches wg maximum (4.981Kpa)
Typical example of Inclined Limb Manometer
Manometers come in many different forms and variations.