2oo3 voting logic for analog input

Hi,

I have three level transmitter and need to implement a logic for voting 2 out of 3 transmitter to make the system more safe. I know the option is there in fail safe systems but I would like to know if any one  done similar logic?

Regards

Sandy

Sensor 1 scaled reading->n1
Sensor 2 scaled reading->n2
Sensor 3 scaled reading->n3
Sensor 1 High Tolerance n1_max = n1*1.01  
Sensor 1 Low Tolerance n1_min =  n1*0.99
Sensor 2 High Tolerance n2_max = n2*1.01
Sensor 2 Low Tolerance n2_min =  n2*0.99
Sensor 3 High Tolerance n3_max = n3*1.01
Sensor 3 Low Tolerance n3_min =  n3*0.99

Next do the following comparisons to find the sensor with incorrect reading

(n1 > n2_min) AND (n1 < n2_max)
AND
NOT ((n1 > n3_min) AND (n1 < n3_max))
AND
NOT ((n2 > n3_min) AND (n2 < n3_max))
= Sensor 3 measures incorrectly

NOT((n1 > n2_min) AND (n1 < n2_max))
AND
(n1 > n3_min) AND (n1 < n3_max)
AND
NOT ((n2 > n3_min) AND (n2 < n3_max))
= Sensor 2 measures incorrectly

NOT((n1 > n2_min) AND (n1 < n2_max))
AND
NOT((n1 > n3_min) AND (n1 < n3_max))
AND
(n2 > n3_min) AND (n2 < n3_max)
= Sensor 1 measures incorrectly

Hope this helps.

Cheers,
Anas

Hi

May be F_2oo3AI (and F_2oo3R) blocks help you.

Please have a look at this thread.

Also:

S7F/FH systems-configuring and programming

And

Analog 2oo3 voting in S7-F/FH Systems for SIEMENS STEP 7 ... YouTube ·   by  Hamid Hosseini

Hope this helps

Regards

hosein