diff --git a/qspace.py b/qspace.py
index 78f0620..0ad6862 100644
--- a/qspace.py
+++ b/qspace.py
@@ -79,7 +79,11 @@ class QSpace3D(Device):
     def UB(self):
         self.dc.ub.UB
 
+    def clear_constraints(self):
+        self.dc.cons.clear()
+
     def set_constraints(self, **kwargs):
+        self.clear_constraints()
         for name, value in kwargs.items():
             setattr(self.dc.cons, name, value)
 
@@ -179,7 +183,7 @@ class QSpace1D(Adjustable):
 h = 6.62607015e-34 # J s
 c = 299792458 # m / s
 e = 1.60217663e-19 # C
-f = h * c / e * 1e-3 * 1e9 *1e3# E [eV] = f / lambda [nm]
+f = h * c / e * 1e-3 * 1e9 *1e4# E [eV] = f / lambda [nm]
 
 
 class Wavelength(Adjustable):