diff --git a/shaketune/measurement/axes_input_shaper.py b/shaketune/measurement/axes_input_shaper.py
index 20c1a58..a0985b2 100644
--- a/shaketune/measurement/axes_input_shaper.py
+++ b/shaketune/measurement/axes_input_shaper.py
@@ -21,6 +21,9 @@ def axes_shaper_calibration(gcmd, config, st_process: ShakeTuneProcess) -> None:
     feedrate_travel = gcmd.get_float('TRAVEL_SPEED', default=120.0, minval=20.0)
     z_height = gcmd.get_float('Z_HEIGHT', default=None, minval=1)
 
+    if accel_per_hz == '':
+        accel_per_hz = None
+
     printer = config.get_printer()
     gcode = printer.lookup_object('gcode')
     toolhead = printer.lookup_object('toolhead')
diff --git a/shaketune/measurement/belts_comparison.py b/shaketune/measurement/belts_comparison.py
index 3296fae..4f5e235 100644
--- a/shaketune/measurement/belts_comparison.py
+++ b/shaketune/measurement/belts_comparison.py
@@ -17,6 +17,9 @@ def compare_belts_responses(gcmd, config, st_process: ShakeTuneProcess) -> None:
     feedrate_travel = gcmd.get_float('TRAVEL_SPEED', default=120.0, minval=20.0)
     z_height = gcmd.get_float('Z_HEIGHT', default=None, minval=1)
 
+    if accel_per_hz == '':
+        accel_per_hz = None
+
     printer = config.get_printer()
     gcode = printer.lookup_object('gcode')
     toolhead = printer.lookup_object('toolhead')
diff --git a/shaketune/measurement/static_freq.py b/shaketune/measurement/static_freq.py
index 17ef82e..bc77251 100644
--- a/shaketune/measurement/static_freq.py
+++ b/shaketune/measurement/static_freq.py
@@ -13,6 +13,9 @@ def excitate_axis_at_freq(gcmd, config) -> None:
     feedrate_travel = gcmd.get_float('TRAVEL_SPEED', default=120.0, minval=20.0)
     z_height = gcmd.get_float('Z_HEIGHT', default=None, minval=1)
 
+    if accel_per_hz == '':
+        accel_per_hz = None
+
     axis_config = next((item for item in AXIS_CONFIG if item['axis'] == axis), None)
     if axis_config is None:
         raise gcmd.error('AXIS selection invalid. Should be either x, y, a or b!')