Introduction

The BMXSAI0410 safety analog input module presents the following features:

  • 4 isolated analog 4...20 mA current input channels.

  • 12500 resolution counts, spanning the data range of 0...25 mA.

  • Current out of range detection, for current values less than 3.75 mA or greater than 20.75 mA.

  • Supports the following SIL3 (IEC61508) standards:

    • The module is able to achieve up to Category 2 (Cat2) / Performance Level d (PLd) using 1 input channel (one-out-of-one (1oo1) evaluation). Thus, Cat1 and Cat2 / PL a, b, c, d can be achieved using 1 input channel.

    • The module is able to achieve up to Category 4 (Cat4) / Performance Level e (PLe) using 2 input channels (one-out-of-two (1oo2) evaluation). Thus, Cat3 and Cat4 / PL d, e can be achieved using 2 input channels.

  • LED diagnostic display provided for the module and for each input channel.

  • Module hot swap during runtime.

  • Module CCOTF when operating in maintenance mode. (CCOTF is not supported in safety mode.)

High Availability

You can design your safety application to varying levels of performance and availability, by using single or redundant input channels and modules, as follows:

Design:

Safety Function Levels:

Input Channels => Modules

SIL

Cat

PL

High Availability?

Single input channel to single input module

SIL3

Cat 2

PLd

–

Single input channel to redundant input modules

SIL3

Cat 2

PLd

✔

Redundant input channels to single input module

SIL3

Cat 4

PLe

–

Redundant input channels to redundant input modules

SIL3

Cat 4

PLe

✔

✔ : Provided

– : Not provided

The following figure illustrates the redundant analog input configuration:

The analog input current value from sensor 1 and sensor 2 are sent by input module 1 and input module 2, respectively, over a black channel to a safety CPU. The CPU executes a dedicated function block, (S_AIHA, in each of two separate, compiled logic programs to manage and select data from the two input modules. This function block operates as follows:

  • If the health status of the input data coming from module 1 is OK, the input data from this module is used in the safety function.

  • If the health status of the input data coming from module 1 is not OK, but the health status of the input data coming from module 2 is OK, the input data from module 2 is used.

  • If the health status of the input data from both module 1 and module 2 is not OK, then the system activates the safety function.