Crimson 3.0 calculations when values are missing

I am trying to calculate total flow from several flow meters, located at disparate sites. The problem is that if one of these sites is off-line the calculation for the sum of total flow from the other site’s flowmeter tags returns a value of “n/a” in the watch window or a series of dashes on the HMI. In other words, Crimson won’t perform the calculation if one or more of the plc gpm values are not present. I have tried setting up other tags that are conditionally either 0 if the remote plc is offline or the gpm value of the plc if it is online, e.g, Tag gpm_offline is defined:

if (isdeviceonline == 1)
return GPM;
else return 0;

As long as plc is off-line, Crimson returns “n/a” for this tag and also returns “n/a” for any other tag that uses a value from plc

The tag for total flows is the internal tag Totalflow, defined as:
return plc1.GPM + plc2.GPM + plc3.GPM + plc4.GPM;

If all of the plc’s in Totalflow are on-line the total flow is calculated correctly.
Any suggestions for calculating the total flow for the plc’s that remain online?

You could create a loop and check the devices states and sum the values based on if they are online or not.
Something like...


Total_GPM := 0;
num_report := 0;
for( i:=1; i < 4; i++)
{
if(isdeviceonline(i) == 1)
{
switch (i)
{
case 1:
Total_GPM := Total_GPM + plc1.GPM;
num_report++;
break;
case 2:
Total_GPM := Total_GPM + plc2.GPM;
num_report++;
break;
case 3:
Total_GPM := Total_GPM + plc3.GPM;
num_report++;
break;
case 4:
Total_GPM := Total_GPM + plc4.GPM;
num_report++;
break;
}
}
}

Thanks, I'll give it a try.