Above: The ANALEXpqA Ferrous Debris Monitor and below, the ANALEXfdM .
Info Centre >> Analex PQ Instruments FAQ >> PQ measurement on ANALEXpqA versus ppm measurement on ANALEXfdM
PQ measurement on ANALEXpqA versus ppm measurement on ANALEXfdM
It is not possible to make a direct comparison for all wear debris types. We have done tests using 3-5 micron ferrous powder suspended in epoxy resin and can get a comparison figure but as soon as you use real samples the picture is quite different.
ANALEXpqA
The ANALEXpqA has a feature called time dependent PQ, this means as the ferrous particles fall towards the sensor head the reading increases. You can get information on particle size by how quickly the reading increases. A fast increase in the readings means a big particle. The reading from the PQ sensor head increases rapidly as the particle gets closer to the surface.
This is because the PQ sensor sensitivity to changes in the magnetic field decreases as a square law of the distance from the sensor head.
So if you have a big particle you will get a larger reading when it settles to the bottom of the sample bottle/pot.
ANALEXfdM
The ANALEXfdM has a more uniform sensitivity as the sample is placed inside the sensor rather than on top of it. This means as the particles fall through the sample the readings change by only a small amount.
Comparing the ANALEXpqA to the ANALEXfdM
If you try to compare ANALEXpqA data in PQ vs ANALEXfdM data in ppm, you immediately run into differences due to different particle size and distribution. This is not an issue if you are new user to PQA or FDM as you can develop a series of trend and alarm levels for your applications.
However if you are already an ANALEXpqA user and want to move to the ANALEXfdM, you must repeat this work to set alarm levels for your applications, you cannot do a straight comparison.
It may be that for some applications the similarity is close, but for others there will be a wide difference.