Note 16 - Segment and Related Information - Information by Industry Segment (Details) - USD ($)	3 Months Ended		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Sales	$ 11,754,219		$ 23,816,735	$ 6,645,780	$ 5,852,924
Income (loss) before provision for income taxes	1,177,991	$ (305,706)	2,188,760	1,333,248	(122,377)
Operating Segments [Member]
Sales	11,754,219	2,356,926	23,816,735	6,645,780	5,852,924
Operating Segments [Member] | Commercial Air Handling [Member]
Sales	9,004,560		11,190,844
Income (loss) before provision for income taxes	905,736		1,424,878
Operating Segments [Member] | Test and Measurement [Member]
Sales	1,161,773	827,066	6,610,684	4,884,778	5,852,924
Income (loss) before provision for income taxes	96,947	(45,409)	1,859,936	143,021	940,016
Operating Segments [Member] | Industrial Hose [Member]
Sales	1,587,886	1,529,860	6,015,207	1,761,002
Income (loss) before provision for income taxes	205,910	389,637	595,939	16,075
Corporate, Non-Segment [Member]
Income (loss) before provision for income taxes	$ (30,602)	$ (649,934)	$ (1,691,993)	$ 1,174,152	$ (1,062,393)