How to read a pressure difference gauge as shown in the figure? ? ?

This differential pressure gauge with static pressure measurement is something I’ve seen for the first time. The position indicated by the small pointer on this gauge (the small dial with positive and negative marks on it likely indicates the differential pressure value) represents the differential pressure value, while the position indicated by the large pointer represents the static pressure value (probably the static pressure on the high-pressure side)

I’ve seen this type of dial for the first time – double tube with two needles?

This post was last edited by qugd on 2018-1-11 at 12:16. The original poster may wish to take a look at this attachment; it shows Brady’s dual needle, dual tube differential pressure gauge. Your diagram shows the following: the red needle represents the static pressure on the low-pressure side, while the black needle indicates the static pressure on the high-pressure side; the difference between the two needles on the small dial is the differential pressure.

According to Brady’s description, the red pin is connected to P+, and the black pin is connected to P_

Isn’t black minus red equal to the current pressure difference?

If that’s the case, then what’s the need for a small dial? One dial is enough. In my opinion, the red needle indicates the differential pressure on the small dial, while the black needle indicates the static pressure on the large dial. This is more reasonable.

The small dial indicates the differential pressure, with positive and negative values.

The red needle is connected to high voltage, while the black needle is connected to low voltage; the difference between high and low voltage is -0.2 MP. The red gauge indicates the correct value!

This differential pressure gauge is read as follows: the red needle indicates the static pressure on the high-pressure side, while the black needle indicates the static pressure on the low-pressure side. The difference between the two needles on the small dial represents the differential pressure. Regarding this type of dual-needle differential pressure gauge, some relevant information is shared in this post: Changhui Instruments, yunrun.com.cn. Dual-needle, dual-tube differential pressure gauges are suitable for measuring two pressures, whether they are the same or different, and can display both of these pressures as well as the difference between them. The products shown in the image are manufactured by Beijing Brady Instrument Co., Ltd. Working principle of the double-needle double-tube differential pressure gauge: The double-needle double-tube differential pressure gauge consists of two separate measurement systems and indicating devices. The measured pressure is determined through the elastic deformation of the pressure-sensing elements; the displacements that occur at the ends of these elements (bourdon tubes) are amplified via a linkage mechanism. The red pointer and black pointer, fixed to the gear shaft, indicate the measured values on the dial respectively, while the small dial in between shows the difference between the two pressures. Original address: yunrun.com.cn/tech/1719.html Instructions for using dual-needle differential pressure gauges: 1. The maximum scale on the dial of a dual-needle, dual-tube differential pressure gauge represents the maximum pressure it can withstand. 2. It is recommended that for dual needle and dual tube differential pressure gauges, the ΔP (differential pressure value = P + —P–) be between one-half and one-third of the dial scale value for optimal performance. If it’s too small, it’s difficult to read. 3. The red needle of the dual-pin differential pressure gauge indicates positive pressure (the input pressure is P+) ； The dial needle indicates negative pressure (output pressure P-). The scale on the dial needle, together with the red needle, forms an angle α; the value can be read directly by looking at the scales on the dial. Alternatively, the differential pressure value ΔP = P1 – P2 can be calculated by using the values indicated by the dial needle and the red needle on the dial respectively. http://yunrun.com.cn/upload/201801/13/201801130036353317.png 4. When the medium is a gas or liquid, it is recommended to use a dual-pin differential pressure gauge indoors, with an operating temperature range of -20~60°C. 5. The minimum range of double-needle differential pressure gauges is generally 0.16 MPa; if a range of 0.1 MPa is required, an accuracy level of 2.5 can be achieved. 6. When installing a dual-pin differential pressure gauge, use the connector with a “+” sign for the input pressure P+, and the connector with a “-” sign for the output pressure P-.