Beckhoff EL33-00 Series Documentation Download

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Appendix

EL33xx-00x0

184

Version: 4.2

// THIS CODE IS ONLY AN EXAMPLE - YOU HAVE TO CHECK APTITUDE FOR YOUR APPLICATION
PROGRAM MAIN
VAR

   nBuffer_INT           : INT;         // Buffer for reading or writing values from/to CoE objects
   aTCElement            : ARRAY[0..9] OF REAL := // Type K µV entries in 10°C Steps:
      [-1156, -778, -392, 0, 397, 798, 1203, 1612, 2023, 2436];
   nTabIndex             : INT;         // Index of node in table

   nT_start              : INT := -300; // -30°C for 0.1°C resolution
   nT_ResTab             : REAL := 100; //  10°C resultion of table (for 0.1°C resolution of values)

   // Variables for calculation:
   // ---------------------------
   nDiff_U_node2node     : REAL;    // Voltage difference of two nodes
   nDiff_U_node2U_TC     : REAL;    // Voltage difference of node and U TC
   nSlope                : REAL;    // Slope for 1st interpolation (temperature to voltage)
   nResidual             : REAL;    // Residual value for interpolation
   nRelation             : REAL;    // Relation for 2nd interpolation (voltage to temperature)
   // ===========================
   nU_TC                 : REAL;     // Voltage of temperature inkl. CJC
   nT_CJ                 : REAL;     // Cold junction temperature
   nU_CJ                 : REAL;     // Corresponding voltage of CJ
   nT_Result             : INT;      // Resulting Temperatur (resolution 0.1°C)
END_VAR

Ausführungsteil (nState=100):

// Cold junction temperature by CoE:
nT_CJ := INT_TO_REAL(nBuffer_INT);
// 1. Convert temperature to voltage:
// ========================================================================
// Determinate index of table:
nTabIndex := TRUNC_INT((nT_CJ - nT_start)/nT_ResTab);

// Calculate difference of two values with real value between them:
nDiff_U_node2node := (aTCElement[nT1]-aTCElement[nTabIndex]);

// Get residual value of real value with integer value:
nResidual := nT_CJ - (nTabIndex * nT_ nT_start);

// Calculate slope nSlope = DY / DX:
nSlope := nDiff_U_node2node/nT_ResTab;

// Calculate interpolated voltage of the cold junction (m*x+b):
nU_CJ := nSlope * nRe aTCElement[nTabIndex];
// ========================================================================

// 2. Add this value to the PDO value:
nU_TC := INT_TO_REAL(nTC_Inputs_Value) + nU_CJ;
// ========================================================================

// 3. Convert calculated voltage to temperature:
// ========================================================================
// Search index of higher target node:
nTabIndex := 0;
// Loop as long U TC is greater than a node:
WHILE nU_TC > aTCElement[nTabIndex] DO
nTabIndex := nTa 1;
END_WHILE
// Loop ended with resulting nTabIndex

IF nTabIndex = 0 THEN
   // Temperature is below first table entry: end here
   nT_Result := nT_start;
ELSE
   // Voltage difference between U_TC and lower target node
   nDiff_U_node2U_TC := nU_TC - aTCElement[nTabIndex-1];

   // Voltage difference between two target nodes with U_TC nested between them:
   nDiff_U_node2node := aTCElement[nTabIndex]-aTCElement[nTabIndex-1];

   // Relation of the two differencies:
   nRelation := nDiff_U_node2U_TC/nDiff_U_node2node;

   // Resulting temperature in 0.1°C resoltion:
   nT_Result := REAL_TO_INT(nT (nRnTabIndex-1) * nT_ResTab);
END_IF