added Iout set via voltage output tune

1 files changed, 22 insertions, 0 deletions

diff --git a/qolab/hardware/power_supply/keysight_e3612a.py b/qolab/hardware/power_supply/keysight_e3612a.py
index bb99bc3..f2720b4 100644
--- a/qolab/hardware/power_supply/keysight_e3612a.py
+++ b/qolab/hardware/power_supply/keysight_e3612a.py
@@ -1,5 +1,6 @@
 from qolab.hardware.basic import BasicInstrument
 from qolab.hardware.power_supply import PowerSupplySCPI
+import time
 
 class KeysightE3612A(PowerSupplySCPI):
     """ Keysight E3612A power supply """
@@ -80,6 +81,26 @@ class KeysightE3612A(PowerSupplySCPI):
         return( float(rstr) )
 
     @BasicInstrument.tsdb_append
+    def setChanIout(self, chNum, val, currentPrecision=5e-6, currentHeadRoom=1e-3, dwellTime=0.1):
+        """
+        Tuning Vout to achieve desired Iout.
+        Generally setting current limit will maintain current near but not exact to desired.
+        This function will try to guess the correct Vout value
+        """
+        iDesired = val
+        self.setChanIlimit(chNum, val+currentHeadRoom)
+        # here we assume that hook up is already made, so we can estimate source resistance
+        for i in range(10):
+            iOut=self.getChanIout(chNum)
+            if abs(iOut-iDesired) <= currentPrecision:
+                break
+            vOut=self.getChanVout(chNum)
+            R=vOut/iOut
+            vDesired = R*iDesired
+            self.setChanVlimit(chNum, vDesired)
+            time.sleep(dwellTime)
+
+    @BasicInstrument.tsdb_append
     def getChanIlimit(self, chNum):
         qstr = f'SOURce:CURR? (@{chNum})'
         rstr = self.query(qstr)
@@ -87,6 +108,7 @@ class KeysightE3612A(PowerSupplySCPI):
 
     @BasicInstrument.tsdb_append
     def setChanIlimit(self, chNum, val):
+        """ Set current limit, seems to be >=0.002 """
         cmnd = f'SOURCe:CURR {val},(@{chNum})'
         rstr = self.write(cmnd)