diff --git a/script/jan/hyst_Dy_singleenergy.py b/script/jan/hyst_Dy_singleenergy.py
index cd3d3e3..2b7d88f 100644
--- a/script/jan/hyst_Dy_singleenergy.py
+++ b/script/jan/hyst_Dy_singleenergy.py
@@ -10,7 +10,7 @@ rrate = 2.0        # ramping speed of mag field
 e1 = 1290.2        # energy 1 (usually on edge)
 e2 = 1283.0        # energy 2 (pre edge)
 
-B1 = 4.0            # field span
+B1 = -4.0            # field span
 B2 = -B1
 nr_loops = 1        # number of loops to acquire