From cf5e348c7dd7141415f5fecfb15251867060e2f4 Mon Sep 17 00:00:00 2001
From: "W. Trevor King" <wking@drexel.edu>
Date: Wed, 14 Mar 2012 18:52:42 -0400
Subject: [PATCH] Raise SurfaceError if surface position data only has a single
 z value.

If the deflection at the minimum position is over the dangerous
threshold, `get_surface_position_data()` will not take any steps in.
With this commit, we avoid raising a ZeroDivisionError in that
situation.
---
 pypiezo/surface.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/pypiezo/surface.py b/pypiezo/surface.py
index 3257e5b..b966b7f 100644
--- a/pypiezo/surface.py
+++ b/pypiezo/surface.py
@@ -176,6 +176,8 @@ def analyze_surface_position_data(
     # Generate a reasonable guess...
     start_pos = int(data['z'].min())
     final_pos = int(data['z'].max())
+    if final_pos == start_pos:
+        raise SurfaceError()
     start_def = int(data['deflection'].min())
     final_def = int(data['deflection'].max())
     # start_def and start_pos are probably for 2 different points
-- 
2.26.2