Related Products: |
EMMK-101, EMMK-102, EMMK-103, EMMC-104, EMMC-105, EMMC-106 |
Related Documents: |
EZDP-2060 |
Type: |
Troubleshooting |
Keywords/Labels: |
sister units, EMI conditions, CT locations |
Summary: |
Describes issues that can affect the signatures when comparing like machines. |
Comparing sister units can be useful in troubleshooting, but you must make sure that the comparisons are valid.
You can compare both the feature values and the spectrum signatures.
However, many other things can affect the signatures when comparing like machines.
-
Regional and local area EMI conditions
At each site the environment is different: different radio stations, different carrier signals, and different equipment emitting EMI noise that affects the background signatures. Research is currently being done to determine if the subtraction of an offline baseline would be appropriate to enhance the comparison between like units at different sites.
-
Different CT locations on same piece of equipment
While you hope that the installer would locate the EMI sensor (RFCT) in the same location for like units, sometimes they do not. In one case, four sister units at the same site had one or more CTs located differently, which affected the ability to compare the unit signatures.
Also, no two “ground” locations are the same. Take care to inspect the ground connection pattern to locate the RFCTs in similar locations (upstream of a Tee vice downstream of a Tee, etc.).
-
Different equipment manufacturing dates
While OEMs tend to have the same base equipment in the same model numbers, sometimes minor changes are implemented as the model number manufacturing progresses. These changes in the structure can affect EMI signature patterns.