pressure units

Andy 1 year ago in IQANdesign updated by Gustav Widén (System support) 1 year ago 4

Being relatively new to Hydraulics and IQAN It seems to me that most experienced folk in that field talk pressures in terms of BAR and others who maybe more peripherally involved use PSI. In my world that means that teh engineers/mechanics/fitters etc use bar and machine operators tend to use psi. As such on most of my HMI designs I have a slider/switch/parameter that can toggle between the 2 so that who ever is using the machine can see their pressures in their measurement of choice.

The calculation between the 2 is not complicated, nor is the building of a structure that allows you to easily swap on the display the visible output between one unit type and the other.....but it gets old having to put multiples of those same building blocks in place to do the conversion and support the visible flag for multiple pressures etc and it makes HMI design a drag as you overlay mutiple gauges etc....

So I was wondering in the (sometime) future if the definition fields for a device like a pressure sensor (but in effect any device) could support multiple measures and either output in terms of a separate output channel for each measures or use an input channel to define which of these comes from a single channel output... For example an SP035 could have  definition 1 as min 0, max 35, unit bar (just as it is today in design) , and definition2 as min 0, max 507.7, unit psi, being effectively the same thing. The downstream math channel or internal digital that does the calculation/ manipulation could access the device choice channel to modify whatever is being done to account for the unit values differences

If the same input channel that determines which device definition output to use was also available to display devices we could also have multiple scales on a single gauges etc rather than multiple gauges that are selected by a visibility channel.

I know its late Friday afternoon as I post this and my brain may have exceeded its weekly whirring amount....Is this something people think could be useful or should I just shutdown for an afternoon beverage earlier in the day :<)


Well I'm still very green with programming, but I'm not afraid to admit that I don't show some J1939 engine parameters because I have no idea how to convert the units to North American standards.  A perfect example would be engine oil pressure.  Would be nice is there was an option to select PSI for instance. 


Engine oil pressure SPN-100 defaults to kPa. Add a math channel. The operator is multiply (*). Operand 1 - SPN-100 Engine oil pressure (kPa) * Operand 2 - 0.145. This converts kPa to PSI. 

Image 3504


We use states in the math channel and switch between states with a 'units" VDIN button that changes the state - converts metric to imperial for display purposes so the operator can choose the units.

Thanks Jamy, I was able to come up with a solution based on your example.  Appreciate you sharing this example.