Note 3 - Revenue Recognition (Details Textual) - USD ($)	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Maintenance Plan, Service Requirement, Period Subsequent to One Year Anniversary of Invoice	1 year
Standard Product Warranty, Term	1 year
Accounts Receivable, after Allowance for Credit Loss, Current, Total	$ 173,443	$ 232,602
Contract with Customer, Liability, Current	$ 20,929	$ 23,065
Maintenance [Member]
Revenue, Performance Obligation, Timing	1 year
Minimum [Member]
Standard Payment Term for Customers	30 days
Maximum [Member]
Standard Payment Term for Customers	60 days