Heidenhain ST 3078 Specto Length Gauges provide TTL output, extended by spring push and available in a right or straight cable exit. SPECTO length gauges have been equipped with a ball-bush guide.

• Low friction, which makes versions of length gauges with reduced gauging force possible
• Safe plunger extension and retraction even with high radial force
• High precision of the measuring loop thank to a guide that is free of play (the bearing and fitted specifically during manufacturing

The gauging force is produced by the spring extending the plunger to the measuring position. The plunger is extended while at rest. The following determines the gauging force:

• The operating orientation (-0.11N, +0.11N)
• The plunger position (over the course of the measure range the force will change)
• The direction of the measurement (whether retraction or extension of the plunger is used)

Heidenhain ST 3078 gauges feature standard clamping shank with 8h6 diameter. Therefore these can easily be used with existing fixtures and stands. There is an option for a special clamping sleeve or clamping bush with one screw each. These make it easier to fasten the length gauge without overloading the 8h6 clamping shank or damaging the ball bush guide. The clamping bush also enables a wide tolerance field for the tightening torque and improves fastening.

Clamping sleeve ID: 386811-01

Clamping bush ID: 1177968-02

Heidenhain ST 3078 Specto length gauge’s plungers are protected by rubber bellows. The bellows are characterized by high resistance to chemical and thermal influences and have a relatively low stiffness. The influence that the bellows have on measurement is relatively low.

Thermal Characteristics: Since temperatures can vary between measurements and can cause changes in the measuring loop. Heidenhain uses special material with low coefficients of expansion for the components of the measuring loop.

Repeatability: Whereas the systems accuracy applies over the entire measuring range, for some applications the repeatability is the decisive factor. It plays an important role in repeated measurements. The repeatability is typically better than the values listed by Heidenhain.

Repeatability depends on: combinations of materials used in the components, installed electronics, optomechanics  used, and the bearing of the plunger. Typically the ST 3078 has a repeatability pf 0.70 um.