Traffic-light colours for readings

Whoever walks past the hall does not want to read 87.3 kPa and think about it. Green means “all good”, yellow “take a look”, red “act now”. One reading and two limits become a traffic light.

Two limits, three colours#

For the hall pressure:

The select cascade#

Start with the most harmless colour and let every worse condition overwrite it:

move colour Color.Green
slt tmp press YELLOW
select colour tmp Color.Yellow colour
slt tmp press RED
select colour tmp Color.Red colour

The order matters: whatever comes later wins. Below 70 kPa “below 90” is true as well – first yellow, then red, and red stays. The other way round, yellow would overwrite the red again.

Failure belongs in there#

A sensor that delivers nothing is a fault. So NaN gets a colour too – the worst one:

snan tmp press
select colour tmp Color.Red colour
select press tmp 0 press     # display shows 0 instead of NaN

Where does the colour go?#

• LED displays have the LogicType Color. Number and colour on one device.
• The small LED (StructureDiode) has Color too – a pure signal light.
• Wall lights and flashing lights have no Color. You give them their colour with the spray can. For a traffic light made of lamps you paint three lamps and switch on the right one:

seq tmp colour Color.Red
sbn LIGHT HASH("Rotlicht") On tmp