diff --git a/script/Marco/power-supply.py b/script/Marco/power-supply.py
index 1d2a28a..f4a0111 100644
--- a/script/Marco/power-supply.py
+++ b/script/Marco/power-supply.py
@@ -60,7 +60,7 @@ SetVA.close()
 ActualVA.close()
 ActualIA.close()
 
-readable =    scan.readables
+readable =    scan.readables[0]
 positions =   scan.writables
 
 threshold = (min(readable) + max(readable))/2