Safety specifications

System requirements

Required Firmware

  • v5.1

Supported Hardware

  • SOMANET Circulo 7

  • SOMANET Circulo 9

Safety parameters


Safety Integrity Level (SIL) according to IEC 61508:2010


Performance Level (PL) according to ISO 13849-1:2015

PL e

Reaction time
SDI1 to STO (without SBC)
SDI2 to STO (without SBC)
SBC/STO triggered by FSoE (with EtherCAT cycle time of 1 ms)


14 ms

14/16 ms
7 ms
7/9 ms
10 ms

Safety parameters IEC 61508:2010

W/O Safe Digital Output used With Safe Digital Output used

Probability of dangerous failure per hour (PFH d)

2.82 x 10 -9 /hour 5.51 x 10 -9/hour

Probability of dangerous failure on demand (PFD avg)

6.17 x 10 -6 1.21 x 10 -5

Safe Failure Fraction (SFF)

99.96% 99.92%

Hardware Fault Tolerance (HFT)

1 1


Type B Type B

Mission time TM

20 a 20 a

Supported demand rate

High, Low High, Low

Safety parameters ISO 13849-1:2015

W/O Safe Digital Output With Safe Digital Output


Cat. 3 Cat. 3

Meantime to dangerous Failure (MTTF d)

64 years 62 years

Diagnostic coverage (DC avg)

99.62% 99.54%

Common Cause Failure (CCF)

> 65 > 65

Installation requirements

Max. installation altitude

2000 m

Pollution Degree

PD 2

Supported Motors

1 × 3-phase BLDC-Motor and 1 active brake

Attention: Servo drives with safety functions shall be used only in Pollution Degree environments class PD 2 according to IEC 61800-5-1:2007. During normal operation only non-conductive pollution may occur, temporarily occurring conductivity caused by condensation may only be expected when the servo drive is out of operation.
PD2 environment can be reached for example with environmentally controlled location which does not contain conductive contamination or by using IP54 enclosure according to IEC 60529:1989 + A1:1999 + A2:2013.

Safe digital inputs (Safe digital inputs other than STO-SBC input)

Safe Digital Input 1 Safe Digital Input 2

Number of digital inputs

2 (dual-channel safety input)

Digital input type according to IEC61131-2:2007

Type 1

Allowed Voltage range

-60 V to +60 V VDC

Max. transient input voltage

80 VDC 566 VDC

Input voltage, logic 1

15-60 V

Input voltage, logic 0

0-5 V

Input current

Max. 6 mA (@24 VDC) Max. 2.3 mA (@24 VDC)
Test pulse filtering (OSSD pulses) 1 ms 5 us

Test pulse detection (OSSD pulses)

Min 1 ms, configurable Min 100 us, configurable

Reverse voltage protected


Allowed discrepancy between digital inputs
(see Encoders and IO)

100 ms

De-activation time

10 ms 5 ms

Safe scaled analog input

Resolution ~ 1.5 mV
Tolerance ±1% *

* can be calibrated by user with safety parameter gain and offset