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diff --git a/docs/source/images/ricker.png b/docs/source/images/ricker.png
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diff --git a/docs/source/images/sine.png b/docs/source/images/sine.png
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diff --git a/tools/plot_builtin_wave.py b/tools/plot_builtin_wave.py
index 20c2a49c..fc81b4aa 100644
--- a/tools/plot_builtin_wave.py
+++ b/tools/plot_builtin_wave.py
@@ -38,7 +38,7 @@ args = parser.parse_args()
 
 # Check waveform parameters
 if args.type.lower() not in Waveform.waveformtypes:
-    raise CmdInputError('The waveform must have one of the following types {}'.format(','.join(Waveform.waveformtypes)))
+    raise CmdInputError('The waveform must have one of the following types {}'.format(', '.join(Waveform.waveformtypes)))
 if args.freq <= 0:
     raise CmdInputError('The waveform requires an excitation frequency value of greater than zero')
 
@@ -57,6 +57,8 @@ while not timeiter.finished:
     waveform[timeiter.index] = w.calculate_value(timeiter[0], dt)
     timeiter.iternext()
 
+time *= 1e9
+
 if args.fft:
     # Calculate magnitude of frequency spectra of waveform
     power = 10 * np.log10(np.abs(np.fft.fft(waveform))**2)