#Stop a test when a reading goes out of range

Give a channel a shutdown limit. The test stops on its own the moment a reading crosses it.

#Before you start

• A Trellis setup open in Phloem Computer. See Trellis.
• The channel you want to watch shows on Live.
• Every output the setup commands has a safe= value.

#Steps

1. Open Trellis in the rail, open your setup, and switch to Code.

2. On the channel's ch.read(...) line, add limits= with the bounds. Add checks=True to arm them:

   Copysetup("heater")
   
   ch = channels()
   ch.read("/demo/temperature", unit="degC", range={"min": 0, "max": 100},
           limits=limits(hi=70, hihi=80), checks=True)
   ch.write("/demo/heater_on", dtype="bool", safe=False)
   
   page("Heater test", layout=col(row(gauge(ch["/demo/temperature"]), alarms())))

   Bound	Does
   hihi	stops the test at or above this value
   lolo	stops the test at or below this value
   hi / lo	warns past this value; the test keeps running

3. Press Deploy. The status chip reads running once the channel reports.

#Check it worked

When the reading reaches hihi:

• The status chip turns tripped.
• An Interlock tripped card reads Outputs held at safe values. It names the bound that fired, such as /demo/temperature hihi.
• Every output goes to its safe= value.

The test stays stopped. Once the reading is back in range, press Reset to re-arm. Until then, Reset is disabled.

Updated November 6, 2026