Introduction

The BMXSAI0410 safety analog input module provides the following diagnostics using its T_U_ANA_SIS_IN_4 device DDT elements:

• input diagnostics

• internal error detection

• channel wiring diagnostics

Input Diagnostics

The sensors connected to each channel are monitored for their ability to accurately measure 10 analog input values between 4 and 20 mA. If the input measurement tests are not successful, the CH_HEALTH bit in the T_U_ANA_SIS_CH_IN DDDT structure is set to 0, indicating it is not operational.

Internal Error Detection

The module processes the input value using two separate, parallel circuits. The two values are compared to determine if an internal error is detected in the module process. If the compared values are different, the IC bit in the T_U_ANA_SIS_CH_IN DDDT structure is set to 1, indicating it is not operational.

Refer to the architecture diagram for the BMXSAI0410 safety analog input module for a visual presentation of this process.

Channel Wiring Diagnostics

The wiring of the sensor to the input channel is continuously diagnosed for a cut wire condition, which is detected when the measured current is less than 3.75 mA or greater than 20.75 mA. In this case, the OOR bit in the T_U_ANA_SIS_CH_IN DDDT structure is set to 1.