diff --git a/labsw/__init__.py b/labsw/__init__.py
index 57417ce..8f5a3fd 100644
--- a/labsw/__init__.py
+++ b/labsw/__init__.py
@@ -1 +1 @@
-__version__ = '0.1.5.7'
+__version__ = '0.1.5.8'
diff --git a/labsw/io.py b/labsw/io.py
index 84cbb3b..459cacb 100644
--- a/labsw/io.py
+++ b/labsw/io.py
@@ -34,7 +34,7 @@ def process_data_RH_logger(filepath, every):
     df = load_data_RH_logger(filepath, every=1)
     # Derivative
     df['dmdt_SG'] = savgol_filter(df['weight'], window_length=10000, polyorder=1, deriv=1)
-    df['dmdt_diff'] = df['weight'].diff(periods=100) / df['time'].diff(periods=100)
+    df['dmdt_diff'] = df['weight'].diff(periods=1000) / df['time'].diff(periods=1000)
 
     h5path = os.path.splitext(filepath)[0]
     h5path += '-processed.h5'