EUCHNER – More than safety.
EUCHNER – More than safety.

STA3A-4121A024MF-EX (Order no. 115586)

Safety switch STA with door monitoring contact, ATEX

  • ATEX version
  • Suitable for use in zones 2 and 22 (gases and dusts)
  • Auxiliary release on the front
  • With door monitoring contact
STA3A-4121A024MF-EX (Order no. 115586)


Approach direction

Horizontal and vertical

Can be adjusted in 90° steps

Solenoid operating voltage

  • AC/DC 24 V +10%, -15%

Guard locking type


Closed-circuit current principle, guard locking by spring force. Release by applying voltage to the guard locking solenoid.

Switching element


Slow-action switching contact 2 NC + 1 NC / 1 NO (door monitoring contact)

Auxiliary release

This is used for releasing the guard locking with the aid of a tool. To protect against tampering, the auxiliary release is sealed with sealing lacquer.

Switching function
Switching function
Dimension drawing
Dimension drawing
Wiring diagram 4121
Wiring diagram 4121
Electromechanical safety switches in use

Functional drawings

Functional drawings

Dimensional drawings

Dimensional drawings
1Auxiliary release
2Cover screw (4x M = 1.5 Nm)
3Locking screw
4Ground the switch via the earth conductor terminal to prevent electrostatic charging (conductor cross-section 4 mm²)
5ATEX cable gland for included (cable diameter 6.5...12 mm)
6Two screw plugs included (M = 2 Nm)

Connection examples

Connection examples
Door monitoring
Solenoid monitoring

Technical data


EAC_RU C-DE.MO05.B.00971/20c_UL_us_E155795_2/1CCC_2020980305000541_CQC2008010305306207

Electrical connection values

Power consumption 8 W
Connection cross section 0.34 ... 1.5 mm²
Rated insulation voltage Ui 50 V
Rated impulse withstand voltage Uimp 2.5 kV
Utilization category
DC-13 4 A 24 V
AC-15 4 A 50 V
Short circuit protection according to IEC 60269-1 4A gG
Solenoid operating voltage
AC/DC 24 V -15% ... +10%
Solenoid duty cycle 100 %
Switching voltage
min. at 10 mA 12 V
Switching current
min. at 24 V 1 mA
thermal rated current Ith 4 A

Mechanical values and environment

Approach speed max. 20 m/min
Approach direction A
Connection type
3 x Cable gland M20 x 1.5
Number of door position NC contacts 1
Number of door position NO contacts 1
Number of guard lock monitoring positively driven contacts 2
Extraction force 30 N
Actuation frequency max. 1200 1/h
Actuating force 35 N
Installation orientation any
Insertion depth 24.5 mm
Clamping range for cable 6.5 ... 12 mm
Mechanical life 1 x 10⁶
Retention force 20 N
Switching principle Slow-action switching contact
Degree of protection IP67
Ambient temperature -20 ... +75 °C
Contact Silver alloy, gold flashed
Housing Die-cast alloy
Locking force Fmax 3000 N
Locking force FZh 2300 N
Guard locking principle Closed-circuit current principle

Characteristic values according to EN ISO 13849-1 and EN IEC 62061

B10DMission time
Monitoring of the guard position1.15x10720 y
Important! Values valid at DC-13 100 mA/24V
Monitoring of guard locking1.15x10720 y
Important! Values valid at DC-13 100 mA/24V

PLMaximum SILCategoryMission time
Control of guard lockingDepending on external control of guard locking20 y


Explosion protection
incl. cable gland II3G Ex nR IIB T4 Gc X /II3D Ex tc IIIC T110°C Dc X

In combination with actuator ACTUATOR-S-G-SN-C2115

Overtravel 5 mm



Complete package

Download all important documents with a single click.


  • The operating instructions and any additions to the operating instructions or brief instructions
  • Any data sheets to supplement the operating instructions
  • The declaration of conformity
Download Complete Package (ZIP, 6,1 MB)

Single Documents

Other Documents

Ordering data

Ordernumber 115586
Item designation STA3A-4121A024MF-EX
Gross weight 0,937kg
Customs tariff number 85365019000
ECLASS 27-27-26-03 Safety switch with guard control

Technical support

Technical support
Do you have technical questions about our products, their possible use or applications? Our experts will be happy to help.

+1 315 701-0315