diff --git a/sensors.py b/sensors.py
index 5abc371..eed1b43 100644
--- a/sensors.py
+++ b/sensors.py
@@ -26,6 +26,8 @@ class Sensor():
 
 class GPIOState(Sensor):
     def __init__(self, pin, transform=lambda x: 1-x):
+        self.measure = 'Switch'
+
         self.pin = pin
         self.transform = transform