FUnction Block for finding the second highest value

[mthompson6782]

I am trying to find a function block to determine the second highest value ( i need the second highest value out of 16 thermocouple temperatures) in a Triconex PLC. Does anyone have a canned version of this they would like to share?

 

[cjd1965]

why don't you think about the problem and suggest your solution then someone may help you

Declare Highest /2nd Highest

If IN1 > IN2 then
Highest=IN1
2nd Highest =IN2
end if

etc

 

[Peter Nachtwey]

Do a bubble sort but stop after two iterations.

 

[L D[AR2P#0.0]]

No need to sort into order, e.g

FUNCTION_BLOCK FB97
VAR_INPUT
T:ARRAY[1..16] OF REAL;
END_VAR
VAR_OUTPUT
SecondHighest:REAL;
END_VAR
VAR
i,j:INT;
END_VAR
BEGIN
j:=1;
//find highest and make it very low
FOR i:=1 TO 16 DO 
 IF T[i] >= T[j] THEN j:=i; END_IF;
END_FOR;
T[j]:=-99999.0;

//find highest again, this will be the second highest
j:=1;
FOR i:=1 TO 16 DO 
 IF T[i] >= T[j] THEN j:=i; END_IF;
END_FOR;
SecondHighest:=T[j];
END_FUNCTION_BLOCK

 

[shooter]

you are telling him too much for the asignement.

 

[mthompson6782]

No need to sort into order, e.g

FUNCTION_BLOCK FB97
VAR_INPUT
T:ARRAY[1..16] OF REAL;
END_VAR
VAR_OUTPUT
SecondHighest:REAL;
END_VAR
VAR
i,j:INT;
END_VAR
BEGIN
j:=1;
//find highest and make it very low
FOR i:=1 TO 16 DO 
 IF T[i] >= T[j] THEN j:=i; END_IF;
END_FOR;
T[j]:=-99999.0;

//find highest again, this will be the second highest
j:=1;
FOR i:=1 TO 16 DO 
 IF T[i] >= T[j] THEN j:=i; END_IF;
END_FOR;
SecondHighest:=T[j];
END_FUNCTION_BLOCK

I really appreciate your response. I think this is exactly what I was trying to do. I have been fiddling around with this and have decided that using structured text is the way to go. I was able to find the second highest using all function blocks but the method i used had problems when the second highest value was the same as the first.

Using function blocks I used the MAX of the 16 inputs then subtracted the max from the original tag values if the value was Not EQUAL to zero it outputted a 1 which I then multiplied again by the original tag values and sent to a MAX block which yielded the second highest. My way is bulky, labor intensive, and clumsy.

I want it so that if the second highest value is equal to the highest value it displays that value twice.

I have read that ST is very much like PASCAL and I have decided to try to sharpen my ST programming skills in this area. Thank you very much.

 

[shooter]

max is also working when you start with 0.