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  1. AC
  2. PLCnext Technology & PLCnext Controls
  3. Wednesday, 21 July 2021
Hey guys, just wanted to check and see if there was something I can do to tame the random values that I am getting from the SE AI 4-20 readings. Using a meter with a steady output, the reading is still jumping several hundredths (ie.. from 60.52 to 60.54 to 60.51, etc...) With a sensor attached its ridiculous. Im even using a filter to average 21 values over a period of time which helps but I still get a fluctuation of a hundredth every couple of seconds..... Ive never really had this problem with Allen Bradley or even BRX, GE, other input cards. I have resolved the following.


  • Everything is properly grounded.
  • No change when isolated or floating.
  • Again, even with a measured ma signal to the thousandth, randomness on the incoming reading is still occuring.
  • Happens on ALL of our PLCnext PLCs (Currently 4)
  • Changing input types (Dword, UINT, DINT, REAL, Etc..) has no effect.
  • We use Phoenix Contact Trio DC-UPS with a steady incoming voltage.
AC Salyers
Electrical Technician
Eduard PLCnext Team Accepted Answer Pending Moderation
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Votes
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Hello AC Salyers,

can I contact you via email and check this behavior together via MS-Teams session?
I would like to verify the raw values as showed in attachment (Set-Point: hex:03E8 dec:1000 mA:+5.0).

Please connect an input channel_1 to the output channel_1 using a cable.

Thanks & Best Regards
Eduard
Attachments (2)
Phoenix Contact Electronics Headquarter - PLCnext Runtime Product Management and Support
AC Accepted Answer Pending Moderation
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Undo
Ive used a precision generator and also ran the output from the SE AO to the SE AI and Im getting the same randomness in ALL of the PLCs
I used UINT for ease of translation but no matter the conversion I use, Im getting the same randomness.

hex dec mА
3E80 16000 +20.0 Reading of (15980 - 16020 UINT)
1770 6000 +10.0 (7979 - 8004)
03E8 1000 +5.0 (3973 - 4011)
0001 1 +4.001 (0 - 6)
0000 0 +4.0 ... +3.2 (0-6)
AC Salyers
Electrical Technician
Eduard PLCnext Team Accepted Answer Pending Moderation
0
Votes
Undo
Hello AC,

I assume you are using the I/O-Modul - AXL SE AI4 I 4-20 - 1088062. The precision of data acquisition is depends on A/D Converter and additional tolerances influenced by electromagnetic interference:
Electromagnetic fields EN 61000-4-3/IEC 61000-4-3 < ±0.5%
Fast transients (burst) EN 61000-4-4/IEC 61000-4-4 < ±0.5%
Conducted interference EN 61000-4-6/IEC 61000-4-6 < ±0.5%

I assume the values 60.52, 60.54, 60.5 are raw values, could you send me details about the used measurement setup:
- Used Precision current generator with tolerances
- Set current in mA

Please send me the measured Raw-values (with floating tolerances) based on following table (see also attached screenshot)

Input data 4 mA ... 20 mA:

hex dec mА
3E80 16000 +20.0
1770 6000 +10.0
03E8 1000 +5.0
0001 1 +4.001
0000 0 +4.0 ... +3.2

Thanks & Best Regards
Eduard
Attachments (1)
Phoenix Contact Electronics Headquarter - PLCnext Runtime Product Management and Support
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