A pressure transducer is a device that converts pressure into an electrical signal, therefore used as a measuring sensor.
Melt pressure transducers are designed to measure pressure in a hot fluid, e.g. melted plastic. They are used in processing machines like extruders, but also in lab instruments like capillary rheometers, where they provide the main raw output of tests (more accurately than force sensors at the crosshead / piston for most applications). Typical range is up to 200 MPa (2000 bar, or 30000 psi), but different ranges are commercially available to match the expected working range with best accuracy.