(5) Instrument zero point unstable
Example 7-26 When there is no flow in the process pipeline of the water flowmeter , the display value is still changing.
①Fault check : The table before stopping production is normal. During maintenance, remove the sensor for inspection and processing. The sensor and electrode should be fine.
②Fault treatment : Please fill the pipe with water first, then close the valves at both ends of the sensor to make the fluid in the pipe fill static. Enter the converter menu and correct the flow zero point to ±0.0000. After zero reset, the zero display value of the flowmeter is stable and no longer changes.
③Repair summary : When the sensors on production have been overhauled, many problems are eliminated, and the instrument has been used for a long time, the zero point may be changed, and the instrument is directly adjusted. Through the inverter menu, you can check whether the contents of each menu meet the initial set value, thereby eliminating the possibility that the flowmeter set value is adjusted by other users.
Example 7-27 The newly installed FIR601 flowmeter fluctuates greatly.
①Fault check : During the process, you must ensure that the pipeline is full and there are basically no bubbles. ; Please close the downstream valve of the sensor to make the pipeline full of non-flowing water. The number is displayed as 0.00%, the output current is 4mA, and the instrument zero point is stable. To reduce display fluctuations, the damping time of the instrument can be appropriately increased.
②Fault handling : adjusts the damping time to 10 seconds, and the display is relatively stable.
③Summary of maintenance : This example shows that fluctuations are not a problem with the instrument. They are fluctuations caused by unstable water flow, and the meter shows the real water flow. The damping time is increased to make the flow displayed by the instrument appear stable, but it will affect the response speed being measured. Long damping time can improve the stability of instrument display and output signals, and is often used in flow control systems; ; shorter damping time can speed up the response to the test, and is often used in the entire accumulation of pulsating flow system.
