diff --git a/frappy_psi/softcal.py b/frappy_psi/softcal.py
index c617bd26..0a246dcc 100644
--- a/frappy_psi/softcal.py
+++ b/frappy_psi/softcal.py
@@ -30,6 +30,8 @@ from frappy.core import Attached, BoolType, Parameter, Readable, StringType, \
     FloatRange, nopoll
 from frappy_psi.convergence import HasConvergence
 from frappy_psi.picontrol import PImixin
+from frappy.lib.mathparser import MathParser
+from frappy.errors import RangeError
 
 
 def linear(x):
@@ -238,3 +240,60 @@ class Sensor(Readable):
 
 class SoftPiLoop(HasConvergence, PImixin, Sensor):
     pass
+
+
+class Function(Readable):
+    rawsensor = Attached()
+
+    formula = Parameter('calib function', StringType(), readonly=False)
+    value = Parameter('physical quantity', FloatRange())
+    _parser = MathParser(x=0)
+    _value_error = None
+
+    def initModule(self):
+        super().initModule()
+        self.rawsensor.registerCallbacks(self, ['status'])  # auto update status
+        if self.description == '':
+            self.description = f'{self.rawsensor!r} with applied function'
+
+    def _get_status(self, rawstatus):
+        return rawstatus if self._value_error is None else (self.Status.ERROR, self._value_error)
+
+    def update_value(self, rawvalue, err=None):
+        if err:
+            err = repr(err)
+        else:
+            try:
+                self.value = self._get_value(rawvalue)
+            except Exception as e:
+                err = repr(e)
+        if err != self._value_error:
+            self._value_error = err
+            self.status = self._get_status(self.rawsensor.status)
+
+    def update_status(self, rawstatus):
+        self.status = self._get_status(rawstatus)
+
+    def write_formula(self, formula):
+        self._parser = MathParser(x=0)
+        self.formula = formula
+        self.read_value()
+        self._value_error = None
+        self.read_status()
+
+    def _get_value(self, rawvalue):
+        try:
+            return self._parser.calculate(self.formula, x=rawvalue)
+        except Exception as e:
+            self._value_error = f'error in formula {self.formula!r}: {e!r}'
+            self.read_status()
+            raise RangeError(self._value_error) from None
+
+    @nopoll
+    def read_value(self):
+        return self._get_value(self.rawsensor.read_value())
+
+    @nopoll
+    def read_status(self):
+        return self._get_status(self.rawsensor.read_status())
+    
\ No newline at end of file