VP MODBUS communication deviation
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The screw-mounted mass flow meters are used on-site; they use Yokogawa VP Modbus communication indoors. A total of 28 mass flow meters are in use, with 12 of them connected in parallel and 16 more connected in parallel. These are connected to two ports of an ALR121 device, and shielding is also applied. Why is the value read on the DCS different from the value on-site? For example, the on-site value is 32030 while the indoor value is 32100. Moreover, the deviation isn’t constant. Currently, a laptop is being used as a slave unit outdoors to send data directly to the indoor system, but there’s still a deviation, and this deviation doesn’t follow any pattern
It seems there’s a higher possibility of interference. If you input the data directly in the control room, will there be errors?
Production wasn’t allowed because there was too much data; it couldn’t be done indoors
It’s not far at all – just 50 meters. The indoor shielding has also been connected
The output of the Rosemount mass flow meter can be adjusted, but it is best not to do so unless it needs to be calibrated; moreover, the deviation is not very large.
As you said, OP, since you’re using a laptop as a remote station outdoors and transmitting data directly indoors, there is still a deviation, but this deviation doesn’t follow any pattern. It’s likely due to interference; also, have terminal resistors been added? ?