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Note 5 - Agreements and Commitments - Changes in Warranty Obligations (Details) - USD ($)
6 Months Ended 12 Months Ended
Jun. 30, 2020
Dec. 31, 2019
Balance $ 813,288 $ 432,225
Warranty costs charged to cost of goods sold 287,847 707,079
Utilization charges against reserve (76,225) (315,556)
Release of accrual related to expired warranties 0 0
Foreign currency effect 6,145 (10,460)
Balance $ 1,031,055 $ 813,288