We need to know the different types of points. Meaning. Is it a AI,DI,DO,AO,Pulse.
Once we know this we also need another tag called AIType,DIType,AoType.
The type might be a bad name but what it will mean is: Is the AI a 10k, 20k, or is it 4-20ma, and so on.
Lastly another tag to add is if it's a 4-20ma, what is the range of the 4-20ma. This will help us run analytics across points. We can find all sensors that have a shelf life of X and see when they need to be changed, or compare them against other sensors to see if there is a drift.
We need to add these tags,as we are adding our own Tag library and we are trying to use Haystack.
Any thoughts on this?
Brian FrankFri 20 May 2011
We already define a kind tag that defines the point as being a Number or a Bool. So that basically covers the digital versus analog classification.
The idea of an input vs and output and actual wiring details like resistance and amperes is interesting. What are these aspects of a I/O typically called?
Winston HetheringtonFri 20 May 2011
I would suggest that Jason's suggestion would be beneficial in the overall scheme of things. Values of points may be more than a number or Boolean value. Looking at the BACnet list of assignable "types" and "ranges", you may note that numbers may be a count (positive or negative) They may be the result of a calculation with x decimal pints or the value of a sensor with a specific range assigned. Boolean points may have various states which in part reports OnOff, however multistage devices use a software to report Off, Run, stage 1, stage 2 or Alm conditions etc. If the reported value does not also have the choice of assigning "Open contact = Off and closed contact = Open (or the reverse of this), the retrieved information may be useless. In the case of multi-step control it is essential to read the text value of the point in it's application instead of only reading the primary Boolean value of "0 or 1". You will find all of the above embedded in the BACnet standard. In my opinion it is essential that the user of extracted data from any source be fully knowledgeable about the manner in which the source data is implemented, otherwise the outcome may be other than that expected.In BACnet and most manufacturers products Points are distinguished by Inputs and Outputs and subsequently followed by a value and a units assignment. Analog Inputs are usually identified by the "AI" designation along with a sensor type and range (which may also distinguish the precision of the sensor). It may also be a calculated value designated by "AV" also with a units assignment. Similarly Boolean or Binary Input points use the "BI" or "BV"(Binary Value) for equated or calculated state followed by assigned units (often text strings for matching the contact condition being monitored) Analog Output Points use the AO, (typically with 0- 100% range) AV for calculated values. with units assigned. ( It should be noted that neither 0% or 100% represents specifically the position of end devices and may be reversed depending on the application for the equipment in question). Binary Output Points use BO or BV(Binary Output Value) along with assigned units (usually text strings which also are assigned to show true conditions of equipment). It might be noted that the BACnet assignments of units are selected and assigned for the benefit of the owner and user at the Human Machine Interface (HMI) to reduce the potential error in critical situations. This is the prime motivator for unit assignment.
Jason Briggs Thu 19 May 2011
We need to know the different types of points. Meaning. Is it a AI,DI,DO,AO,Pulse.
Once we know this we also need another tag called AIType,DIType,AoType.
The type might be a bad name but what it will mean is: Is the AI a 10k, 20k, or is it 4-20ma, and so on.
Lastly another tag to add is if it's a 4-20ma, what is the range of the 4-20ma. This will help us run analytics across points. We can find all sensors that have a shelf life of X and see when they need to be changed, or compare them against other sensors to see if there is a drift.
We need to add these tags,as we are adding our own Tag library and we are trying to use Haystack.
Any thoughts on this?
Brian Frank Fri 20 May 2011
We already define a
kindtag that defines the point as being aNumberor aBool. So that basically covers the digital versus analog classification.The idea of an input vs and output and actual wiring details like resistance and amperes is interesting. What are these aspects of a I/O typically called?
Winston Hetherington Fri 20 May 2011
I would suggest that Jason's suggestion would be beneficial in the overall scheme of things. Values of points may be more than a number or Boolean value. Looking at the BACnet list of assignable "types" and "ranges", you may note that numbers may be a count (positive or negative) They may be the result of a calculation with x decimal pints or the value of a sensor with a specific range assigned. Boolean points may have various states which in part reports OnOff, however multistage devices use a software to report Off, Run, stage 1, stage 2 or Alm conditions etc. If the reported value does not also have the choice of assigning "Open contact = Off and closed contact = Open (or the reverse of this), the retrieved information may be useless. In the case of multi-step control it is essential to read the text value of the point in it's application instead of only reading the primary Boolean value of "0 or 1". You will find all of the above embedded in the BACnet standard. In my opinion it is essential that the user of extracted data from any source be fully knowledgeable about the manner in which the source data is implemented, otherwise the outcome may be other than that expected.In BACnet and most manufacturers products Points are distinguished by Inputs and Outputs and subsequently followed by a value and a units assignment. Analog Inputs are usually identified by the "AI" designation along with a sensor type and range (which may also distinguish the precision of the sensor). It may also be a calculated value designated by "AV" also with a units assignment. Similarly Boolean or Binary Input points use the "BI" or "BV"(Binary Value) for equated or calculated state followed by assigned units (often text strings for matching the contact condition being monitored) Analog Output Points use the AO, (typically with 0- 100% range) AV for calculated values. with units assigned. ( It should be noted that neither 0% or 100% represents specifically the position of end devices and may be reversed depending on the application for the equipment in question). Binary Output Points use BO or BV(Binary Output Value) along with assigned units (usually text strings which also are assigned to show true conditions of equipment). It might be noted that the BACnet assignments of units are selected and assigned for the benefit of the owner and user at the Human Machine Interface (HMI) to reduce the potential error in critical situations. This is the prime motivator for unit assignment.