diff --git a/frappy_psi/ionopimax.py b/frappy_psi/ionopimax.py
index ec9572a2..dbcd4411 100644
--- a/frappy_psi/ionopimax.py
+++ b/frappy_psi/ionopimax.py
@@ -100,6 +100,7 @@ class DigitalOutput(DigitalInput, Writable):
 
     def write_target(self, value):
         self.write(self.addr, value == self.true_level, 1)
+        self.read_value()
 
 
 class AnalogInput(Base, Readable):
@@ -142,8 +143,7 @@ class VoltageInput(AnalogInput):
 
 class SimpleVoltageInput(AnalogInput):
     """version for iono pi"""
-    scale = 1e-3
-
+    scale = 1e6 / 1024  # probably a firmware or documentation error
 
 class LogVoltageInput(VoltageInput):