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Note 5 - Agreements and Commitments - Changes in Warranty Obligations (Details) - USD ($)
3 Months Ended 12 Months Ended
Mar. 31, 2020
Dec. 31, 2019
Balance $ 813,288 $ 432,225
Warranty costs charged to cost of goods sold 226,079 707,079
Utilization charges against reserve (51,643) (315,556)
Release of accrual related to expired warranties
Foreign currency effect (17,679) (10,460)
Balance $ 970,045 $ 813,288