added calculation for Hallprobe calibrated Field offsets

cfg/main/flamemag_cfg.py

@@ -224,3 +224,14 @@ Mod('T_main_switch',
     channel='Main Coil Switch',
     main='main',
 )
+
+Mod('Calib',
+    'frappy_psi.cryoltd.Absfield', '',
+    main='B',
+    bx='Bx',
+    by='By',
+    bz='Bz',
+    bx_offset=0.0,
+    by_offset=0.0,
+    bz_offset=0.0,
+)

frappy_psi/cryoltd.py

@@ -27,7 +27,7 @@ changed from the client is fixed for at least 10 seconds.
 """
 import re
 import time
-from math import copysign
+from math import copysign, sqrt
 from frappy.core import HasIO, StringIO, Readable, Drivable, Parameter, Command, \
     Module, Property, Attached, Enum, IDLE, BUSY, ERROR
 from frappy.errors import ConfigError, BadValueError, HardwareError
@@ -603,3 +603,32 @@ class Compressor(Channel, Drivable):
         """reset error"""
         self.sendcmd('Set:Compressor:Reset <CH>')
         self._error_text = ''
+
+class Absfield(Readable):
+    """
+    Keep track of the magnet hysteresis and provide corrected readbacks
+    """
+    main = Attached()
+    bx = Attached()
+    by = Attached()
+    bz = Attached()
+
+    bx_offset = Parameter('Hysteresis offset for Bx', FloatRange(unit='G'),
+                          readonly=False, default=0.0)
+    by_offset = Parameter('Hysteresis offset for By', FloatRange(unit='G'),
+                          readonly=False, default=0.0)
+    bz_offset = Parameter('Hysteresis offset for Bz', FloatRange(unit='G'),
+                          readonly=False, default=0.0)
+
+
+    calib_bx = Parameter('hysteresis-corrected Bx', FloatRange(unit='G'))
+    calib_by = Parameter('hysteresis-corrected By', FloatRange(unit='G'))
+    calib_bz = Parameter('hysteresis-corrected Bz+B', FloatRange(unit='G'))
+    value = Parameter('hysteresis-corrected total magnitude of the field', FloatRange(unit='G'))
+
+    def read_value(self):
+        self.calib_bx = self.bx.value - self.bx_offset
+        self.calib_by = self.by.value - self.by_offset
+        self.calib_bz = self.bz.value+self.main.value - self.bz_offset
+
+        return sqrt(self.calib_bz ** 2 + self.calib_by** 2 + self.calib_bx** 2)