When receiving unstable values with significant fluctuations in the analog input module?
Possible reasons are as follows:
- It is possible that the analog input module and the field sensor use self powered or isolated power supplies, but the two power supplies are not connected to each other, that is, the power supply of the analog input module and the signal ground of the field sensor are not connected; This will generate a high common mode voltage with up and down vibrations, affecting the analog input value.
Another reason may be that the wiring of the analog input module is too long or the insulation is poor, which can be affected by electromagnetic interference.
The following methods can be used to solve the problem:
- Connect the negative terminal of the on-site sensor to the common M terminal on the module to compensate for this fluctuation. (However, it should be noted that this is the only connection between the two power systems.)
The background is:
The analog input module is non isolated internally;
The common mode voltage must be less than 12V and greater than -12V;
The common mode rejection ratio for 60Hz interference signals is 40dB.
- Use analog input filtering.
Click on “Device View” and select the module that needs to set up analog input filtering; As shown in Figure 1:
Select the channel that needs to be filtered;
Select the filtering strength.
