Common causes of error in the calibration of precision pressure gauges

Precision pressure gauges often encounter problems during calibration. Here are some common causes of failures summarized by the editor based on years of experience. Hope they can give you a reference:

1. Needle of precision pressure gauge does not return to zero.

It is mainly if the elastic inertia of the spring tube pressure gauge cripples the tube after a period of use, causing the initial displacement of the spring tube to change, i.e. that the long-term elastic sequelae makes the elastic inertia larger, which can be studied as zero drift. The common way to eliminate this defect is to fix the needle, which involves opening and closing the needle of the pressure gauge when the pressure calibrator is not under pressure, and fixing it again at the zero position, so that the current home position is used. as zero point to complete zero point adjustment. . In the mwave, pressure gauge accuracy after needle calibration is mainly in accordance with the original requirements, such as return error, linearity, precision and displacement of tapping. Most of them are qualified. If it is not ideal, other measures can be taken according to the theoretical situation.

2. Firmware of precision pressure gauge is loose.

If the pointer does not return to zero and the calibration is not satisfactory after the needle is attached, the reason is that the attachment is loose. The main reason is that the adjusting screw connecting the pull rod and the sector gear is loosened and its original position is changed, resulting in the failure of the tube The expansion multiple of the displacement changes, causing the indication of the pressure gauge needle become larger or smaller. After adjusting the position of the set screw under the standard pressure and fixing it, theexpansion multiple of the original pressure gauge can be restored to make the needle indication accurate. In addition, check whether the fixing screw behind the pressure gauge core is loose, and whether the connecting fixing pin between the spring tube and the pull rod is broken.

3. The central gear of the precision pressure gauge is badly worn locally.

This fault often occurs when the pump outlet pressure is unstable. The pressure range is unstable. For example, the pressure gauge at the outlet of the piston pump is repeatedly unstable in a pressure range for a long time, resulting in repeated mesh changes between the sector gear and the central gear, and the friction increased leads to the damage of certain gears. Therefore, the gauge board group may simply not return to zero and the indication is inaccurate. To eliminate these defects, only the geare central and sector gear can be replaced. During operation, they can be replaced together by replacing the lower fixed bottom plate.

4. The hairspring becomes weaker or damaged.

It also mainly occurs when the pressure is unstable again and again, and the long-term stretching and shrinking of the hairspring weakens its elasticity. If the north side pressure treatment line is pressurized or the gauge guide tube is frozen or condensed causing the gauge needle to swing and damage the hairspring, this can also be repaired by replacing the bottom plate .

5. The spring tube of the precision pressure gauge is deformed.

The deformation mentioned here mainly refers to the elastic deformation, which often appears on the current pressure gauge. The spring tube core of the first pressure gauge is thick regardless of the tube wall et of the tube diameter, so that the impact capacity and elastic inertia of the spring tube are small, that is, Hooke\'s law has a large limit and a long service life, from so that the spring tube pressure is used for a long time——The displacement does not change the relationship (the change is small). The wall and diameter of the spring tube used by the current pressure gauge manufacturers is very thin, the pressure resistance and elasticity of long-term use becomes worse, and the service life is shortened. The linear area keeps getting larger, which makes the limit of the linear pressure-displacement relationship smaller, so there is no linearity or even the phenomenon of direct deformation and distortion of the pressure gauge spring tube , and even poses the risk of leakage. Spring tubes with non-linear changes can only be scrapped.

To summarize, the 5 points above sdiscovered, repaired and adjusted during the process of calibrating precision pressure gauges. Calibrating pressure gauges is also part of the maintenance process. Calibration is not allowed for unqualified personnel and the calibration process occurs. The data should be used as the original records for the calibration record form and gauge inspection certificate, which in turn will be used to determine if the gauge accuracy is qualified. In addition, during the ibration and maintenance calprocess, the mandatory ticket should be filled in, and the discarded pressure gauge should be filled out with the discarded form and the circulation form, so that the accounts are consistent.

Prev: Typical Faults and Troubleshooting Methods in the Spectrophotometer