In a recent project, 15 PT100 temperature transmitters and 4 pressures were installed in the electric cabinet, all of which were made of three-core shielded cables, with reliable grounding (Signal PE independent grounding)
, 1 inverter, CPU226, 5 analog modules.
In the actual debugging, it is found that as long as the inverter is running, there are two temperature simulations that fluctuate greatly. After the inverter is turned off, the temperature curve is very natural. I think that the source of the interference can only be the inverter, there is no way, and many experts agree that only the dear inverter can be removed from the electric cabinet (
Originally considered to be able to visually see the inverter output frequency in practice)
After being installed on the shelf on the fan site, the effect is very obvious, and the temperature curve is naturally taking its exclusive path.
Summary: 1. There are also many posts about signal interference in the forum. Whether everyone is making the same mistake is to install the inverter in an electric cabinet containing analog access. (
The most convenient way is to install it directly to the load site without repeating the mistake. )
2. When using the inverter, it is necessary to fully follow the principle of using the inverter, and add a filter to the input and output of the inverter to prevent the high-frequency electromagnetic wave generated by it from being superimposed on the analog channel.
3. All measuring lines should be shielded cables, and the two ends of the shielding should be grounded. Do not mix with the grounding wire of the inverter. Remember! ! !