Note 11 - Segment and Related Information - Information by Industry Segment (Details) - USD ($)	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Sales	$ 11,878,700	$ 3,346,315
Income (loss) before provision for income taxes	498,336	221,267
Operating Segments [Member] \| Commercial Air Handling [Member]
Sales	9,115,937
Income (loss) before provision for income taxes	865,205
Operating Segments [Member] \| Test and Measurement [Member]
Sales	1,071,847	1,770,071
Income (loss) before provision for income taxes	(128,949)	734,228
Operating Segments [Member] \| Industrial Hose [Member]
Sales	1,690,916	1,576,244
Income (loss) before provision for income taxes	100,189	425,970
Corporate, Non-Segment [Member]
Income (loss) before provision for income taxes	$ (338,109)	$ (938,931)

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045

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Period Type:	duration