Heidenhain ST 1288 Specto Length Gauges provide 1Vpp output, extended by spring 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)

Heidenhain ST 1288 Specto length gauges built in spring extends the plunger to the measuring position to produce the gauging force. While at rest the plunger is extended. The following criteria will determine the measuring force:

• The operating orientation (-0.08 N, +0.08 N)
• The plunger position (over the course of the measuring range the force changes)
• The direction of the measurement (whether extension or retraction of the plunger is used)

An 8h6 diameter clamping shank comes standard with ST length gauges. Therefore these Heidenhain length gauges can easily be used with existing measuring fixtures and standards. Special clamping sleeves and clamping bushes are also available. 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 1288 Specto length gauges are protected by a rubber bellows. The bellows has 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 1288 has a repeatability pf 0.25 um.