First, the use of the product status of customers
Customer Information:
Shaanxi Hydraulic System Co., Ltd. (supported to provide hydraulic equipment for large machine tools)
Product number:
MPM5581 intelligent pressure switch (MPM5581-G8-1KA-C1-R5-MS901)
Use overview:
The customer produces a small hydraulic system for use on the machine tool. Two MPM5581 intelligent pressure switches are installed to monitor the system pressure. An analog quantity of 4-20mA is required, the switch operating point is set at 15Mpa, and the output is 24VDC after the operation. The computer system controlling the machine tool takes action. Pressure switches and other components (solenoid valves, etc.) are supplied via an external 24VDC supply. As shown below:
Second, on-site problems and real-time processing
Overview of the problem:
1. After the customer installs the 5581 pressure switch on his equipment, he converts 220VAC into 24VDC through a DC voltage regulator. After the product is connected, it is not powered on. (There is a case where the DC source fuse is burned out)
2. After the salesman communicates with the customer, the resistance between VCC and GND is measured when the product is not powered. They are: 12 ohms, 6 ohms, and the matched cable not connected to 5 meters is measured through the air plug. The situation is the same.
3. The site was replaced with a switching power supply (24V 2.1A) to supply power to the product. A product was found to have a sizzle and no display. The other product showed no response and no display. The resistance between VCC and GND was measured. They were: 7 Europe, 2 Europe.
Third, the problem analysis
Preliminary judgment:
The TVS tube on the circuit board is damaged. After the device was replaced, the test product returned to normal and was displayed after power-up, and the measurement was also normal after pressurization. Because in the previous hydraulic industry users did not have such problems, and the product was tested during the design process over-voltage protection experiments. Considered comprehensively: customer site power supply problems.
Processing content:
(1) Bring two repaired MPM5581 pressure switches to the site to determine the cause of the product problem, communicate with the customer, and assist the customer in the follow-up product use protection measures.
(2) To introduce the company's hydraulic industry-related products and information to customers, and make preparations for product consultation and later-stage business.
Field analysis:
The cross-validation was adopted in conjunction with the on-site power supply, and the product was tested after installation with different collocations and power supply methods.
Mode 1: 220VAC is converted into 24VDC by the on-site DC voltage regulator source. After the DC voltage source is shown to be stable at 24V, the pressure switch is connected to the 24VDC working voltage and the product works normally.
Mode 2: According to the customer's field device connection, the MPM5581 pressure switch is installed and connected to the line, and the DC voltage source switch is turned on to provide power. The products are not displayed. Analyze the circuit board on the spot, find the TVS tube of the power module area is damaged, replace the component, repair the circuit board.
Mode 3: The site is replaced with a switching power supply (24VDC 2.1A). After the line power is connected, the pressure switch is displayed normally.
Method 4: According to the customer's field device connection method, connect the MPM5581 pressure switch, solenoid valve and other electrical equipment (working voltage is 24VDC), use the DC voltage source, the pressure switch does not display after power on. Analyze the circuit board on the spot, find the TVS tube of the power module area of ​​a pressure switch is damaged, the TVS of many pressure switch many area is destroyed and MCU is damaged too.
Mode 5: Replace the switching power supply, and connect the other way according to the mode 4. After the power is turned on, the pressure switch works normally and the voltage display is normal. The switch point and analog output meet the technical requirements of the customer.
Analysis result:
(1) The DC power supply used by the customer is a linear DC voltage regulator. In the process of switching, the instantaneous voltage is up to about 90V, and in general, it reaches about 50V to 60V. This is only through digital observation. The value obtained does not include the higher instantaneous voltage that the delay may cause, and the voltage value of the pressure switch is designed to be 40 VDC, which has completely exceeded the over-voltage range that the product can withstand. In the past, similar customer sites use switched DC voltage regulators to provide a stable DC operating voltage.
(2) The power supply to the MPM5581 pressure switch is possible after the linear DC voltage source is stabilized, but with the solenoid valve, the pressure switch performance is not displayed, and the current of the voltage regulator is displayed by 0.1A/0.2. A becomes about 1.24A.
(3) Switching DC voltage regulators are used to supply power to the pressure switch alone or to the solenoid valve at the same time. The pressure switches are all working properly.
in conclusion
1. The customer approves the results of on-site analysis and agrees to follow-up when supplying the next-level customer equipment and debugging the MPM5581 switch. The power supply adopts a switch-mode DC power supply.
2. At present, the product liquid system has been used on the machine tool and it is working properly.
3. The company provides each user with the best quality on-site technical support and services, and shares their valuable experience in the use of sensor products.
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