Heidenhain ST 1277 Specto Length Gauges provide TTL output, extended by pneumatic (air) push and available in a right or straight cable exit. Specto length gauges have been equipped with a ball-bush guide.

Some of the basic properties of ball-bush guides are:

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

Pneumatic Plunger Actuation: The Heidenhain ST 1277 gauge is extended by the application of compressed air. When the air is ventilated out the plunger retracts back to its protected resting position. The gauging force can be adjusted as needed through the level of air pressure used.

• The operating orientation (-0.07 N, +0.07 N)
• The plunger position (can be adjusted through the air pressure level)
• The direction of the measurement (whether extension or retraction of the plunger is used)

ST 1200 length gauges come standard with 8h6 diameter clamping shanks. These Heidenhain length gauges can therefore easily be used with existing measuring fixtures and standards. Heidenhain also offers the choice of a special clamping sleeve or a clamping bush each containing one screw. The accessories 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 tightening toque and improves fastening.

Clamping Sleeve ID: 386811-01

Clamping Bush ID: 1177968-02

The plungers of the Heidenhain ST 1277 Specto length gauges are protected by a rubber bellows. The bellows have high resistance to chemical and thermal influences, and have relatively no stiffness. There is little to no influence on the gauges mechanical behavior and measuring force.

Thermal Characteristics: Heidenhain length gauges have a defined thermal behavior. While temperature variations during measuring can result in changes to the measuring loop; Heidenhain uses special material with low expansion coefficients for the components of the measuring loop.

Repeatability: System accuracy applies over the entire measuring range, the repeatability can be a more decisive factor for applications. It plays a very important role in the repeated measurement of the product. The repeatability of the length gauge 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 1277 has a repeatability pf 0.25 um.