diff --git a/Makefile b/Makefile
index a6527069079966ca7acb6bca0b2909410c739ee1..8b4cc128158abe41a943af12c9ad2e9128b58b06 100644
--- a/Makefile
+++ b/Makefile
@@ -9,4 +9,8 @@ start:
 	@echo Starting supervisord
 	supervisord -c supervisord.conf
 
+stop: 
+	@echo Shutting down supervisord
+	supervisorctl shutdown
+
 .PHONY: build start stop
diff --git a/README.md b/README.md
index d5fb2b408986a9c837f9519ecd4e6b314f7bbada..26ae185feb91b3c82549acc7bb628b5f821dd2c4 100644
--- a/README.md
+++ b/README.md
@@ -72,6 +72,8 @@ a group of processes. Use the ``supervisorctl help`` to find out more and
 ``supervisorctl help COMMAND`` to get a detailed description of the
 corresponding command.
 
+To shut down the monitoring service completely, use ``make stop``.
+
 
 ## Configuration file
 
diff --git a/scripts/time_residuals.py b/scripts/time_residuals.py
index 9750ffad3ee36684c49c037bae7f1d2ef35be92d..a1667c7cc5f8841411c30b12991d3950662e9dc1 100644
--- a/scripts/time_residuals.py
+++ b/scripts/time_residuals.py
@@ -35,20 +35,24 @@ def main():
     hours = 2
 
     while True:
+        print("Reading data...")
         df = pd.read_csv(args['TIME_RESIDUALS_FILE'])
         df = df[df.timestamp > time.time() - 60 * 60 * hours]
+        print(f" -> number of entries: {len(df)}")
 
         fig, axes = plt.subplots(nrows=6,
                                  ncols=3,
                                  figsize=(16, 10),
                                  sharex=True,
-                                 sharey=True,
+                                 sharey=False,
                                  constrained_layout=True)
 
         for ax, floor in zip(axes.flatten(), range(1, 19)):
             for du in np.unique(df.du):
                 _df = df[df.du == du]
                 t_res = _df[_df.floor == floor].t_res
+                t_res = t_res[np.abs(t_res) < 500]
+                print(f"   DU {du} floor {floor}: {len(t_res)} entries")
                 ax.hist(-t_res,
                         bins=100,
                         histtype='step',