Complex sentence: From 1887 to 1892, with airship designer Rudolf Hans Bartsch von Sigsfeld (1861-1902), he developed a psychrometer for accurate measurement of atmospheric humidity, which was the first instrument that was able to provide a reliable temperature reading of hot-air balloons.
Split into simpler sentences: From 1887 to 1892, with airship designer Rudolf Hans Bartsch von Sigsfeld (1861-1902), he developed a psychrometer for accurate measurement of atmospheric humidity. This was the first instrument that was able to provide a reliable temperature reading of hot-air balloons.