Heidenhain Metro Length Gauges come in ranges 12 mm, 25 mm, 30 mm, 60 mm, and 100 mm. The 12, 25, and 30 mm have 1Vpp output while 60 and 100 mm have 11uApp output.
Metro length gauges are designed with ball-bush guides. The following are some of the basic properties of ball-bush guides in HEIDENHAIN length gauges: 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 thanks to a guide that is free of play (the bearing and plunger are specially fitted during manufacture).
The Heidenhain MT 12×1 and MT 25×1 come with a built in spring that extends the plunger to the measuring position and produces the gauging force. While at rest the plunger is extended. The gauging force depends on the following criteria:
Pneumatic plunger actuation: The MT 1287 and MT 2587 length gauges are extended by the application of compressed air. When the air connection is ventilated, the integral spring retracts the plunger to a protected resting position. The gauging force can be adjusted to the measuring task through the level of air pressure. At constant pressure, it depends on the operating orientation and the plunger position.
Motorized plunger actuation: The MT 60 M and MT 101M length gauges feature an integral motor that moves the plunger. Required is a switch box, SG 60M OR SG 101M, which is connected to the gauge where it can be operated up and down through the push of a button or over the connection of external actuation. Plungers cannot be moved by hand if the switch box is connected. The gauging force of these motorized length gauges is adjustable in three stages through the switch box. The force remains constant over the measuring range but depends on the operating orientation.
External plunger actuation via gravity: The MT 60K and MT 101K along with special version of the MT 1200 and MT 2500 plunger is freely movable. There is an optional coupling with a moving machine element for position measurements. The force needed to move the plunger specified ad required moving force.
Mounting: The MT 60 and MT 101 length gauges are fastened by two screws onto a plane surface. These screws ensure a mechanically stable installation of even these large gauges. Special holders are available for fastening the MT 60 and MT 101 to the MS 100 gauge stand for the Heidenhain Metro length gauge.
The MT 1200 and MT 2500 length gauges feature a standard clamping shank with 8h6 diameter. Therefore these Heidenhain length gauges can be easily used with existing measuring fixtures and stands. Heidenhain offers a special clamping sleeve and clamping bush with one screw each. These accessories will make it easier to fasten the length gauge without overloading the 8h6 clamping shank of damaging the ball-bush guide. The clamping bush also enables a wide tolerance field for the tightening torque and improves fastening. Sleeve: ID 386811-01/Bush: ID 1177968-02
Thermal dynamics: Heidenhain length gauges have a defined thermal behavior. Since temperatures can vary during the measurement process and possibly cause a measuring loop, Heidenhain uses special low coefficient of expansion material for the components of the measuring loop.
Repeatability: Whereas the system accuracy applies over the entire measuring range, for some applications the reliability is the decisive factor. It plays an important role in repeated measurements. The repeatability of the length gauges is usually better than the values listed by Heidenhain. Reliability depends on the combination of materials used in teh components, installed electronics, optomechanics used, and the bearing of the plunger.
MT 101: 0.04um/MT 1200: 0.03um/ MT 2500: 0.09um/ MT 60: 0.06um