We call it transducer and the others may know it as a probe or sensor.
It is a part of Prisma DI-5 and Prisma DI-5C deflection indicator instrument.
The standard transducer is 89 mm and it can be extended by using extension bars up to 565 mm.
There is a small transducer as well which is 60 mm and it can be extended up to 536 mm.
The transducer of Prisma Deflection Indicator is connected with the display unit by 7 meter cable.
The technical inspector is setting in the transducer between the crank webs to measure the deflection on diesel and gas engines.