BERNSTEIN602.1137.103Metal-Bodied Limit Switch, Steel Rod Actuator on Repositionable Turret Head, 1 NC + 1 NO Slow-Action, Positively Opening NC, IP65

Product Description

What this part is

This is a Bernstein GC series metal-bodied limit switch with a rod actuator — a robust mechanical position switch for machine guarding, end-of-travel limits and position monitoring. The switch body is die-cast aluminium with a sheet aluminium cover, the turret head carries a steel rod that is deflected by the moving machine element, and inside are one normally closed and one normally open contact.

Decoding the type designation

GC – Bernstein’s metal-enclosed limit switch series, die-cast aluminium bodyU1 – slow-action contact block with one NC and one NO contact. This is the letter to watch: the parallel SU1 designation (GC-SU1 AD, article 6021187125) is the snap-action version. Same body, same actuator, different switching behaviour — see below, because this is the difference that matters most.AD – rod actuator on a turret head (Zn die-cast head, steel rod). The neighbouring actuator codes on the same body are AV, AH (adjustable lever), AF, FF, IW, RIW, HIW, KU, W and others, all separate article numbers.
The article number is written both as 602.1137.103 and 6021137103 — Bernstein uses the dotted form in catalogues and the undotted form in its own PIM system, and both are worth searching.

Slow-action versus snap-action: read this before you buy:
This unit is the slow-action variant, and it is a deliberate engineering choice rather than a lesser option.

In a slow-action switch the contacts move at a speed proportional to the actuator movement. The changeover point is highly repeatable and directly related to actuator position, which is what you want when the switch is defining a precise mechanical position. Slow-action is also the conventional choice where the NC contact must be forced open by direct mechanical action — there is no spring-over mechanism between the actuator and the contact bridge to interpose a failure mode.

In a snap-action switch (the GC-SU1 AD) an over-centre spring flips the contacts quickly regardless of how slowly the actuator moves. That gives cleaner make-and-break on higher currents and less contact bounce at very low actuation speeds, at the cost of a less position-exact switching point and some differential travel.

The rule of thumb: if the switch is defining a position, slow-action; if it is switching a meaningful load and the actuator may creep, snap-action. They share the same body and actuator and are not the same part.

Positively opening NC contact

The NC contact in this switch is a positively opening (direct opening action) contact — in Bernstein’s circuit diagrams these carry the standard direct-opening symbol. That means the actuator forces the NC contact open through a rigid mechanical link, so the contact cannot remain welded shut while the actuator is depressed. It is the property that makes a mechanical position switch usable in a safety-related circuit, and it is the reason a switch like this is specified for guard monitoring rather than a plain microswitch.

The contact configuration is Bernstein type Zb: a galvanically isolated changeover contact. The two contacts are electrically separate from each other, so the NC and NO can sit in different circuits at different potentials — typically the NC in the safety chain and the NO signalling to the PLC.

Published specifications

Enclosure: die-cast aluminiumCover: sheet aluminiumActuator: turret head (Zn die-cast) with AD rod (steel)Actuator head: repositionable by 4 x 90°Contact type: 1 NC, 1 NO, type Zb (galvanically isolated changeover), slow-actionNC contact: positively openingAmbient air temperature: −30 °C to +80 °CMechanical life: 10 x 106 operating cyclesSwitching frequency: up to 100 per minuteMounting: 2 x M4Connection: 4 screw terminals (M3.5)Terminal designation: to DIN EN 50013Conductor cross-sections: solid 0.5 to 1.5 mm², or stranded with ferrules 0.5 to 1.5 mm²Cable entry: 1 x M20 x 1.5Weight: approximately 0.22 kgInstallation position: operator definableProtection: IP65 to IEC/EN 60529

What these specs mean in practice

Ten million operating cycles at up to 100 per minute is a genuine industrial duty rating — run at one operation per second continuously, that is years of service. This is a switch for a production machine, not for occasional actuation.

The die-cast aluminium body and IP65 rating are why you specify a GC over a plastic-bodied switch: it survives being knocked, it tolerates coolant and washdown spray, and it will not crack if the machine element overtravels into it. The metal actuator suits high mechanical loads.

The turret head repositioning by four 90° steps is a practical installation feature. You can mount the switch body where the bracket allows and then rotate the head so the rod faces the moving element, instead of fabricating an adaptor plate. Decide the orientation at installation, because it determines the direction of actuation.

−30 °C to +80 °C covers unheated buildings, cold stores and hot areas near ovens or drives.

M20 x 1.5 is the single cable entry, and the terminals accept 0.5 to 1.5 mm² — adequate for control wiring, not for power. Terminal designations follow DIN EN 50013, so the numbering will match a standard European wiring diagram.

What is not included

Switch only, as pictured. Not supplied: the M20 x 1.5 cable gland (the entry is threaded, the gland is a separate item and you need one to achieve the IP65 rating), the cable, mounting screws for the 2 x M4 holes, brackets or mounting plates, ferrules, and any actuating cam, ramp or striker on the machine side. Bernstein offers a latching function on this series on request; unless a unit is specifically ordered that way it is non-latching, and neither unit here should be assumed to latch.

Installation and setup notes

Set the turret head orientation before you make off the cable — it rotates in four 90° positions and you want the rod presented squarely to the moving element. Approach the rod so the machine element deflects it rather than striking it end-on; a rod actuator is designed for lateral deflection and driving it axially will bend it. Fit a proper M20 gland and tighten the cover; the IP65 rating depends on both. Wire the positively opening NC contact into the safety or stop circuit and use the NO for signalling, not the other way round. If the switch is part of a safety function, the overall Performance Level depends on the whole chain — switch, logic and actuator — and must be assessed for the machine as a whole; this switch’s positively opening contact is a necessary condition, not a sufficient one.

Quantity and configuration

Two units in stock, sold individually. A matched pair is useful for the two ends of a single travel axis, where identical switching characteristics on both limits is worth having.

Interchange guidance

Search forms include GC-U1 AD, GCU1AD, 602.1137.103, 6021137103 and 602-1137-103. Within the GC series treat these as related models, not equivalents: GC-SU1 AD (6021187125) is the snap-action version of this exact switch; GC-U1 AV (6021136104), GC-U1 AH (602.1135.102), GC-U1 AF (602.1139.106) and GC-U1 FF (602.1140.476) are the same slow-action body with different actuators; GC-U1Z and GC-A2Z / GC-E2 variants have different contact arrangements including 2 NC, 2 NO and overlapping contacts. All will bolt to the same 2 x M4 pattern and then behave differently, which is exactly the substitution to avoid. Bernstein is a German manufacturer and the GC series remains a current catalogue range with published datasheets, so a like-for-like new switch is available.