Zero-start Fully Automatic Digital Piston Pressure Gauge

Piston pressure gauge is designed on the principles of hydrostatic equilibrium and Pascal's law, balancing the force exerted by pressure on the piston against the gravity of weights; because standard weights provide the balancing force, it is also called a dead-weight piston pressure gauge. Weights are placed on the hanging carrier at the top of the measuring piston; the piston rod is inserted into the cylinder and its lower end bears the pressure Po produced by the working medium.

When the pressure acting on the lower end balances the mass of the piston rod and its accessories, hanging carrier and weights, the piston rod is lifted and stabilises at a certain position, and the pressure reading is P = (m1 + m2 + m3)·g / A, where P is the measured pressure (Pa); m1, m2, m3 are the masses of the piston rod and its accessories, the hanging carrier and the weights (kg); A is the effective area of the piston (m²); and g is the local gravitational acceleration (m/s²). Since m2 and m3 are fixed and very stable over time, the piston rod (usually made of tungsten steel) does not wear during rotation so m1 and the area A stay stable, and g does not change if the location is unchanged—so wherever high accuracy and stability are required the piston pressure gauge is used as the standard, and it also serves as the national primary standard.

Although highly stable and widely applied, conventional piston pressure gauges have two drawbacks:

(1) the mass of the piston rod, accessories and hanging carrier cannot be eliminated, so a lower measuring limit exists and multiple gauges are needed to cover the full range; and (2) weight mass cannot be infinitely small, so the pressure interval caused by the minimum weight makes continuous pressure output impossible—hence automatic standard pressure generators that output a continuous, zero-start pressure signal are now more widely used. This product integrates modern digital pressure measurement, mass metrology and computer technology with the high-accuracy, stable and reliable piston pressure gauge, combining the advantages of both digital and piston gauges into an all-new modular, high-precision, high-stability, digital and information-based digital piston pressure gauge—another major innovation in China's pressure-metrology history.

Working principle of the company's digital piston pressure gauge:

A high-precision balance is installed beneath the hanging carrier, magnetically coupled to it; moving the balance changes the magnetic force, and when the magnetic force balances the weight of the hanging carrier, piston rod and accessories the lower limit can be made infinitely low. When a decimal pressure is entered on the screen, the balance reading is obtained by calculation, and by moving the balance the output pressure is controlled at the set value.

By organically combining pressure-sensor technology, mass metrology and the piston pressure gauge, it displays the piston's output pressure digitally with multiple pressure-unit display functions, while retaining the high accuracy, long-term stability and reliability of a piston pressure gauge; it keeps the accuracy class of a piston gauge yet extends the usable range, and displays pressure, rotation speed, working position and temperature. Range: digital piston operation can be realised for any range within 60 MPa.