This eliminated the need for mercury manometers. Dixon was an expert on the theory and use of manometers. Tsien's experiments included plotting of pitot pressures using mercury-filled manometers. Soon after, water-filled manometers were designed. Gauges that rely on a change in capacitance are often referred to as capacitance manometers. The measurement devices can be manometers, pressure transducers, or analog chart recorders.