Don't Stop at the Dynasties of the Gauge

As we all know, to understand the hydraulic performance of hydraulic components and the pressure and flow conditions of hydraulic systems, measuring instruments must be used. Pressure gauges have been used to measure pressure for hundreds of years. The advantages are low cost, direct reading, and no intermediate links. 

Limitations of using pressure gauges:

1) Poor dynamic performance (below 10Hz);

2) It passed by in a flash, the process was not recorded, and it was impossible to analyze it in depth;

3) The transmission of information can only rely on imprecise language descriptions, and there is no basis for verbal statements.

The limitations of pressure gauges can be avoided by using a recording pressure gauge, such as a "hydraulic multimeter":

1) The dynamic performance of modern pressure measurement sensors is higher than 5000Hz, which is enough to capture the pressure of general hydraulic component systems.

Force transients are then analyzed calmly.

2) Information can be transmitted, communicated, analyzed, and discussed objectively and without loss, even between regions that use different languages.

There are many benefits to learning to use recording measuring instruments

Example 1, electro-hydraulic proportional valve controls the motor

Manufacturer B wants to replace the valves made by A with the valves they make. In an application, after the B valve is replaced, the inspector of the user unit feels that the performance of the B valve is different from that of the A valve, and also provides different pressure gauge readings. Factory B sent people there three times, but the problem was not solved because no recording measuring instrument was used.

The author was invited to investigate. Pressure sensors were installed at the original pressure gauges on both sides of the motor. Using a recording measuring instrument, the pressure conditions of the two valves were recorded under the same operating conditions. According to the comparison of the test results, it can be clearly seen that under the same driving current, the inlet pressure pA, the B valve is lower than the A valve; the outlet pressure pB, the B valve is higher than the A valve. When the test results were sent to Factory B by e-mail, the leaders and relevant technicians immediately understood where the problem was, so they could make corresponding improvements, so that the performance was basically the same as that of A valve.

Example 2, Pump B replaces Pump A

Two constant pressure pumps are connected in parallel to supply oil to the hydraulic cylinder through the reversing valve. The pump manufactured by Factory B has been installed and used for several months, but the user is still worried that the pump of B may affect the use due to slow response. The author installs a pressure sensor at the original pressure gauge, asks the user to start each pump separately, and records the change of pressure during the process of switching to the working position and hydraulic cylinder movement, and puts these two processes together on a map with data processing software, which can clearly It can be clearly seen that when switching to the working position, the response of the variable mechanism of the B pump is faster than that of the A pump, so the pressure drops less and can maintain a higher pressure than the A pump. It proves that on this occasion, the user's worries are unnecessary. In this application, the pressure is constantly changing. Although the change is not rapid during the period from 16s to 21s, and you may be able to barely get some feeling by observing it with a pressure gauge, but during the period from 11s to 12.5s, it is impossible to grasp the change in pressure with a pressure gauge.

The author has been using recording measuring instruments since working in a German factory in 1990, which has helped solve many technical problems. And many hydraulic component system manufacturers in Europe that have been inspected used recording testers in the factory test and after-sales service in that era. Therefore, the author believes that whether the recording tester will be used can be used as a gauge to measure the technical level of hydraulic enterprises.

- No matter how many expensive processing machine tools are imported, if there is no quick recording tester, it still works by pressure gauge. It is still not possible to test the performance curve of the product by itself, and the product manual can only be copied from foreign countries. As a hydraulic company, it can only be considered a low level.

- If an enterprise has a recording tester, there are several people who can use it, and some people can roughly understand the test curve, which can be regarded as an intermediate level.

- If the factory test and after-sales service personnel generally use recording testers to collect data, and there are a group of technical "masters" who can analyze and discuss the test records, this kind of enterprise can be regarded as a truly high-level enterprise.

- If the test results can be reproduced by digital simulation, it is a high level of research.

Now, due to the development of electronic technology, the euro has fallen, even if the simplest configuration of the recording tester (hydraulic multimeter) produced in Germany is sold in China for less than 20,000 yuan. Therefore, the purchase cost should not be an obstacle for most domestic enterprises. Buying an instrument is easy, however, this is only the first step. No tester is low tech. With a tester, it will not work, and it is still a low-tech level. Difficult to use. Because this requires combining theory with practice, there is considerable practice in hydraulic technology. It is more important to learn to use the tester to improve the technical level, to be able to analyze the test results, and to let the curve speak for itself. A German engineer told the author that the complete set of hydraulic systems they provide to customers must be tested after assembly, and then analyzed, improved, and archived based on the test results.

The test results are very comprehensive, but also very complicated, requiring a lot of experience to understand and analyze. And the actual workplace is often very harsh, and the time available for testing is often very limited. So you should start with a simple hydraulic circuit on your own test bench. Seeing the micro-knowledge, a drop of water can also reflect the sun's rays.