PMV position feedbacker
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Does anyone know the specific principle behind this position feedback? On-site debugging is quite simple; when one component broke, I took it back, disassembled it to take a look, but there are still some things I don’t quite understand. In my understanding, the red button on the positive and negative sides must be a switch that is connected to the cam; it determines whether the valve operates in an open or closed state. But what is the purpose of this? What’s the use of those 2 sets of switch contacts in the upper right corner? And that CW CCW thingy must be a variable resistor, right? What does xo mean again? When should the two sets of slots next to it, cw and ccw, be used? Is there a detailed circuit diagram?
For the large board with a double-sided circuit, if you spend enough time looking at it, you can draw it out by yourself; as for the small board, it’s not possible to tell whether it has two sides or three layers. According to its instruction manual, the contact feedback is separate from the 4–20mA circuit; the attached document is the instruction manual (in English) downloaded from its official website
We have these too; let’s exchange debugging experiences
This post was last edited by liuyun001 on 2019-5-11 at 13:12. It can be fairly assumed that the red ones are microswitches, which provide UPPER (upper limit) and LOWER (lower limit) dry contact signals (one set each for NO/NC); the corresponding terminal blocks are NC (1, 2, and 4, 5) and NO (1, 3, and 4, 6).
The component with black, yellow, and red wires in the lower left corner appears to be a potentiometer; it likely provides an analog output corresponding to position, and it is presumed to correspond to terminals 7, 8, and 9. The above views are not supported by any evidence and are for reference only
When you are testing 4-20ma, if the fine adjustment there doesn’t work, do you just remove the panel to adjust the gear directly?
Is the red microswitch used to set the upper and lower limits for fine adjustment?
When the cam moves to the UPPER position, it presses the reed of the microswitch, causing the dry contacts inside the switch to close or open； When the cam moves to the LOWER position, it releases the reed of the microswitch, causing the dry contacts inside the switch to open or close.