Can you please share the complete specifications? I've limited experience, but the details in the table might have more explanations if we read the rest of the document.

Perhaps this is a special purpose sensor. I face a difficulty in linking parameters together but maybe it's simply because it's a sensor type I'm not familiar with. 

Regards- Ali M. Al-Shurafa 

It is a velocity sensor 

Please look at attached file

This probe is less commonly used nowadays. I saw it mounted on large machinery like forced draft fans in power plants where the speed is relatively low. It's more common on balancing machines (feild or shop) specially from IRD. Some portable (route) vibration programs use this type of probe also.

I can't give a definite answer to your question but my guess based on my understanding of this sensor is that the dynamic range (125 mil pp) would be the reliable reading range from the generated electric signal while the probe travel (375 mil pp) would be the physical movement of the internal component before it hits the design limits. The term dynamic range here is used in a different context to what some practionors use.

I'll see if I can have one of these sensors and measure the travel to verify my guess. As you may know there is more than one design of these. Some have an extended rod (perhaps 1/8" dia, 1" longe, opposite side to the cable) that measures the vibration. The sensor can measure vibration as the rod moves.

I hope this helps a little. 

Regards- Ali M. Al-Shurafa

I went back to an old (perhaps too old) manual form IRD and found this specification for another (but similar model). Your model is Model 546DP while the below specs are for Model 544.

I've also checked an old 546DP to measure how much the rod can retract and extend. The span I found is about 0.5".

I hope this helps a little.

Regards- Ali M. Al-Shurafa