The user guide referenced in the document you linked explains it fairly clearly.
Traditional velocity sensors consist of either a moving wire coil surrounding a fixed magnet or a fixed wire coil surrounding a moving magnet. The Velomitor® Sensor is more accurate than traditional velocity sensors. Because the Velomitor® Sensor contains no moving parts, it is also more durable and less sensitive to transverse motion than traditional seismic transducers. Its piezoelectric sensing element and solid-state circuitry let the Velomitor® Sensor withstand years of continuous use.
The Velomitor® Sensor is a two-wire device that requires an external power supply. The power supply must provide a DC voltage of 22 to 30 Volts and a current of 10 mA. A constant current diode must be used to limit the current to the sensor to 2.5 to 6 mA. Figure 1-1 shows a simple block diagram of the Velomitor® Sensor system. [Emphasis mine.]
Table 3.1 gives the required diode part number:
3 mA (Motorola P/N 1N5309) current diode Bently Nevada P/N 00643485.
Wiring seems to be as simple as this.
simulate this circuit – Schematic created using CircuitLab
Figure 2. General gist of your amplifier.
The datasheet mentions a DC bias on the output so you're going to need to remove that before amplification. C1 does that. You'll need to pick a value that will allow the lowest frequencies of interest through without too much attenuation.
R3 and R4 bias the op-amp to half supply so that your signal can swing symmetrically about that point. You don't say what this is feeding into so I have no idea if this will work in your application.
I had never heard the term before. Thanks for the education.