SLC500 Daily Totalizer

cbass

Member
Join Date
May 2008
Location
BOOKHAM
Posts
2
Trying to get my head around totalizers, instantanious and daily , anyone got some examples for me to look at and crib from ?

I'm totalizing large volume flows, where flows of 400 litre/sec are normal...giving 34560000 litres per day.... then Im going to move this daily total onto an iconics scada. Am I correct in assuming this number ( daily total in Litres) is too big for an N register? and will cause a maths overflow error ( and fault processor) ? what pitfalls should I be aware of if I use an F register for the total value ?


many thanks...

chaz
 
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34,560,000 liters is bigger than you can represent in a 16 bit integer (+32767). Convert to m3 doesn't help in that regard either. Its also big enough that you will loose resoltion in the 1's column of a floating point number, your resolution will be larger than 10 liters, thats not a limitation of the PLC, its a limitation of how floating point numbers are represented.

There are also other issues with accurate totalizing in the PLC that have to do with timing. These have been discussed in other threads on the forum. Do a search on totalizer and totalizing
 
Forgot to add a picture

Alaric said:
34,560,000 liters is bigger than you can represent in a 16 bit integer (+32767). Convert to m3 doesn't help in that regard either. Its also big enough that you will loose resoltion in the 1's column of a floating point number, your resolution will be larger than 10 liters, thats not a limitation of the PLC, its a limitation of how floating point numbers are represented.

There are also other issues with accurate totalizing in the PLC that have to do with timing. These have been discussed in other threads on the forum. Do a search on totalizer and totalizing
What you could do is set up registers to calculate the volume x 1,000, or x 10,000.

For instance, you could set up the logic such that if the volume in your totalizer is greater than 1000, then add 1 to a register designated as (volume x 1,000) or (volume x 10,000) and clear the totlalizer.
This way you can use your totalizer as a count of the volume under 1,000 or 10,000 and you can use the other register in the SCADA and just multiply the value left to get the actual value.
 
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