frappy_psi.thermofisher: add limits

also switch off control when T is outside limits by more than
security_margin

Change-Id: I3df513c7bc36ca23bf249c61fdfadb39870db3a5

frappy_psi/thermofisher.py

@@ -20,7 +20,7 @@
 """bath thermostat Thermo Scientific™ ARCTIC A10 Refrigerated Circulators"""
 
 from frappy.core import Command, StringIO, Parameter, HasIO, \
-    Drivable, FloatRange, IDLE, BUSY, ERROR, WARN, BoolType
+    Drivable, FloatRange, IDLE, BUSY, ERROR, WARN, BoolType, Limit
 from frappy.extparams import StructParam
 from frappy_psi.convergence import HasConvergence
 
@@ -34,7 +34,7 @@ class TemperatureLoopA10(HasConvergence, HasIO, Drivable):
     ioClass = ThermFishIO
     value = Parameter('temperature', unit='degC')
     target = Parameter('setpoint/target', datatype=FloatRange, unit='degC', default=0)
-    control_active = Parameter('circilation and control is on', BoolType(), default=False)
+    control_active = Parameter('circulation and control is on', BoolType(), default=False)
     ctrlpars = StructParam('control parameters struct', dict(
         p_heat = Parameter('proportional heat parameter', FloatRange()),
         i_heat = Parameter('integral heat parameter', FloatRange()),
@@ -43,6 +43,11 @@ class TemperatureLoopA10(HasConvergence, HasIO, Drivable):
         i_cool = Parameter('integral cool parameter', FloatRange()),
         d_cool = Parameter('derivative cool parameter', FloatRange()),
     ), readonly=False)
+    target_min = Limit(default=-99)
+    target_max = Limit(default=199)
+    security_margin = Parameter('security margin for automatic switch off',
+                                FloatRange(), default=1)
+    _off_reason = None
 
     status_messages = [
         (ERROR, 'high tempr. cutout fault', 2, 0),
@@ -89,7 +94,12 @@ class TemperatureLoopA10(HasConvergence, HasIO, Drivable):
         """
         Reading internal temperature sensor value.
         """
-        return self.get_par('T')
+        value = self.get_par('T')
+        if value > self.target_max + self.security_margin:
+            self.switch_control_off('T above limit')
+        elif value < self.target_min - self.security_margin:
+            self.switch_control_off('T below limit')
+        return value
 
     def read_status(self):
         """ convert from RUFS Command: Description of Bits
@@ -132,15 +142,24 @@ class TemperatureLoopA10(HasConvergence, HasIO, Drivable):
                     # else our own status
                     return BUSY, conv_status[1] if 'tolerance' in conv_status[1] else status_msg
                 return status_type, status_msg
-        return WARN, 'circulation off'
+        return WARN, (self._off_reason or 'circulation and control off')
 
     def read_control_active(self):
         return int(self.get_par('O'))
 
+    def initialReads(self):
+        super().initialReads()
+        self.target_max = min(self.target_max, self.get_par('RHTF'))
+        self.target_min = max(self.target_min, self.get_par('RLTF'))
+
+    def switch_control_off(self, reason=None):
+        self._off_reason = reason
+        self.control_active = self.set_par('O', 0)
+
     @Command
     def control_off(self):
         """switch control and circulation off"""
-        self.control_active = self.set_par('O', 0)
+        self.switch_control_off()
 
     def read_target(self):
         return self.get_par('S')