Note 6 - Revenue From Contracts With Customers - Disaggregation of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net revenues	$ 20,160	$ 17,352	$ 60,128	$ 47,420
Semiconductor Market [Member]
Net revenues	11,415	9,162	34,997	29,756
Industrial Market [Member]
Net revenues	5,576	5,232	16,229	7,530
Telecommunications Market [Member]
Net revenues	2,051	1,661	4,673	6,552
Other Non-semiconductors Markets [Member]
Net revenues	1,118	1,297	4,229	3,582
Thermal Testing Products [Member]
Net revenues	6,544	5,418	18,964	18,552
Induction Heating Products [Member]
Net revenues	6,150	4,341	17,709	6,067
Semiconductor Production Test Products [Member]
Net revenues	5,245	5,383	17,393	17,598
Service and Other Products [Member]
Net revenues	2,221	2,210	6,062	5,203
End User [Member]
Net revenues	17,186	15,877	51,687	43,392
OEM and Integrators [Member]
Net revenues	$ 2,974	$ 1,475	$ 8,441	$ 4,028