TechTip: Dynamic Limits and Tolerance Using a Macro on Weintek HMI

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Lamonde Automation TechTip on using dynamic limits and tolerance calculation on Weintek HMIs using a macro

In this TechTip, we’re looking at using dynamic limits in numeric objects, alarm colours, and using a macro to calculate the limits based on a +/- tolerance.

In the demo program, the “Actual” value is in LW-0, the “Target” is in LW-2, “Tolerance” in LW-4 and LW-10 & LW-12 are Lower and Upper limits respectively.

Setting dynamic limits and alarm colour/behaviour

The macro code deals with the case of a 0 target, and also negative target and negative limits:


macro_command main()

float target = 0 // target value
float tolerance = 0 // tolerance
float percent = 0 // percentage tolerance
float upper = 0 // upper dynamic limit
float lower = 0 // lower dynamic limit

GetData(target, "Local HMI", LW, 2, 1) // get target value

GetData(percent, "Local HMI", LW, 4, 1) // get target value

target = target * 100

tolerance = (target / 100) * percent // target / 100 x percentage

if target == 0 then //  if target is 0... then
lower = (target + percent) // lower limit is target + percent
upper = (target - percent) // upper limit is target - percent
else // otherwise...
lower = (target - tolerance)/100 // lower limit is target - tolerance
upper = (target + tolerance)/100 // upper limit is target + tolerance
end if


if upper < 0 or lower < 0 then  // if either go negative
SetData(lower, "Local HMI", LW, 12, 1) // then swap upper/lower
SetData(upper, "Local HMI", LW, 10, 1)
else if target == 0 then // or if target 0 then normal upper lower
SetData(lower, "Local HMI", LW, 10, 1) 
SetData(upper, "Local HMI", LW, 12, 1)
else // or if target positive then
SetData(lower, "Local HMI", LW, 10, 1) // normal
SetData(upper, "Local HMI", LW, 12, 1) // 
end if

end macro_command
Alarm condition “Actual” is flashing red as it is outside the tolerance limits
Alarm condition “Actual” is Black as it is within the tolerance limits

Demo program available to download here.