Differences between diaphragm boxes, diaphragms, and Bourdon tube pressure gauges

What do the codes in the instrument, such as YTNP-100HF2, and any other codes, mean? Is there any documentation available to help me understand this? I’d like to figure it out.

This post was last edited by Shutong on 2020-8-9 at 22:07. The measurement methods and classifications of pressure sensing instruments are not limited to the three types listed by the original poster; in modern industrial production, pressure is measured over a wide range of values, under various conditions, with different accuracy requirements. As a result, there are many types of pressure sensing instruments. Based on differences in their sensitive elements and conversion principles, they are generally divided into the following four categories: (1) Liquid-column type pressure sensing instruments. It is a instrument that converts the pressure to be measured into a liquid column height based on the principles of hydrostatics; it uses a glass U-tube or single tube filled with liquids such as water or mercury for measurement. Instruments that operate on this principle include single-tube pressure gauges, U-tube pressure gauges, and inclined-tube pressure gauges. (2) Elastic pressure measuring instruments. It is a instrument that converts the pressure to be measured into displacement, based on the principle of deformation of elastic elements under stress. Commonly used elastic elements include Bourdon tubes, diaphragms, and bellows. Instruments that operate on this principle include Bourdon tube pressure gauges, diaphragm [or diaphragm-box] pressure gauges, and bellows-type pressure gauges. Such instruments are mainly used for indicating pressure on-site. (3) Electrical pressure measurement instruments. These are instruments that use sensitive elements to directly convert the pressure being measured into various electrical quantities such as resistance, voltage, capacitance, and charge amount, in order to carry out measurements. Instruments that operate on this principle include strain-gauge pressure gauges, Hall-effect pressure gauges, capacitive pressure gauges, etc. Such instruments are often used to transmit pressure signals over long distances to the control room for centralized pressure indication. (4) Piston-type pressure measuring instruments. These instruments operate on the principle of hydraulic pressure transmission; they convert the pressure to be measured into the mass of a counterweight applied to the piston area in order to carry out the measurement. Piston pressure gauges have high measurement accuracy, with allowable errors that can be very small. 0.05% – 0.02%; it is usually used as a standard instrument for testing and calibrating pressure measuring devices.

A Bourdon tube, also known as a spring tube, is a tube that is bent into various shapes such as arcuate, spiral, or S-shaped; it has a flat or oval shape, with the short axis of its cross-section aligned with the radial direction of the tube’s bend. When the pressure inside the spring tube is higher than the pressure outside, the inner surface area in the direction of the short axis is larger than that in the direction of the long axis; as a result, a greater force acts on this area, causing the tube’s cross-section to tend to become circular – that is, the short axis lengthens while the long axis shortens, leading to elastic deformation. At this point, the free end must move in the direction that straightens the tube.   Deformation stops when the elastic force caused by deformation is balanced by the force generated by pressure. The displacement generated at the free end drives the amplification mechanism via a lever, causing the pointer to deflect by a certain angle; the scale then indicates the magnitude of the pressure being measured.

Principle of diaphragm pressure gauge: Under pressure, the medium being measured acts directly on the elastic diaphragm, causing it to deform elastically upward (for measuring positive pressure) or downward (for measuring negative pressure). This deformation triggers a linkage mechanism fixed at the center of the diaphragm, which in turn rotates the gear shaft of the movement, allowing the pointer to indicate the measured pressure value on the dial.

Working principle of diaphragm pressure gauge: When using a diaphragm pressure gauge (also known as a diaphragm-type gauge) to measure pressure, the medium under measurement acts directly on the diaphragm, causing it to deform upward. The pressure of this medium is transmitted to the Bourdon tube through the fluid filled inside it, resulting in elastic deformation at the end of the Bourdon tube. This deformation, in turn, drives the gear shaft of the movement via a linkage mechanism, allowing the pointer to indicate the measured pressure value on the dial

This post was last edited by Shutong on 2020-8-9 at 22:26. The main differences between diaphragm pressure gauges and case-type pressure gauges are as follows: 1) Different elastic elements: The elastic element in a diaphragm pressure gauge is a Bourdon tube, while the diaphragm serves only as a separating element. The elastic element of a diaphragm pressure gauge is a corrugated diaphragm. The measured pressure acts on the diaphragm, causing it to deform elastically upward (or downward); the pressure value is indicated through a linkage mechanism welded to the diaphragm. 2) Different accuracy grades: Diaphragm pressure gauges generally have an accuracy grade of 1.6, while diaphragm-type pressure gauges have an accuracy grade of 2.5. 3) Different measurement ranges: