Note 18 - Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($)	Mar. 31, 2018	Mar. 31, 2017
Inventory reserves	$ 50,000	$ 785,000
Accrued vacation	343,000	475,000
Stock option compensation	67,000	108,000
Property and equipment	264,000	169,000
Warranty reserve	25,000	39,000
Accounts and notes receivable reserve	103,000	290,000
Employee severance reserve	549,000	460,000
Net operating loss carryforwards	6,083,000	6,461,000
Federal/Canadian tax credits	4,486,000	4,648,000
263A inventory capitalization		10,000
Unrealized gains/losses and outside basis difference for CFC's	2,324,000	1,995,000
Intangibles	25,000	43,000
Other	69,000	78,000
Total deferred tax assets	14,388,000	15,561,000
Deferred revenue	(11,000)	(35,000)
Prepaid expenses	(337,000)	(505,000)
263A inventory capitalization	(28,000)
Bargain purchase gain	(179,000)
Gain on marketable securities (OCI)	(72,000)	(94,000)
Outside basis difference	(270,000)	(34,000)
Total deferred tax liabilities	(897,000)	(668,000)
Net deferred tax asset (liability)	13,491,000	14,893,000
Less valuation allowance	(13,583,000)	(14,698,000)
Net deferred tax liability	$ (92,000)
Net deferred tax asset		$ 195,000