Heidenhain ST 1287 Specto Length Gauges provides 1Vpp output, extended by pneumatic (air) push and available in a right or straight cable exit. Specto length gauges are 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 1287 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 length gauges come standard with 8h6 diameter clamping shanks. Therefore these Heidenhain length gauges can easily be used with existing measuring fixtures and standards. Heidenhain 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 1287 Specto length gauges are protected by a rubber bellows. 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 coefficients of expansion for the components of the measuring loop.

Repeatability: In some instances the repeatability of the measurement is more important than the accuracy over the entire measuring range. 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 1287 has a repeatability pf 0.25 um.