Consolidated Statements of Cash Flows (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash flows from operating activities:
Net income	$ 2,001,974	$ 5,450,918	$ 4,518,384
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense	464,670	388,904	261,859
Change in fair value of derivative instrument	(209,370)
(Gain) loss on disposition of long-term assets	(52,024)	7,029	11,627
Depreciation and amortization	1,949,782	616,451	544,341
Deferred income taxes	(549,049)	(173,311)	(234,390)
Excess tax benefit from employee stock plans	(98,210)	(208,067)	(101,830)
Changes in operating assets and liabilities net of effects from purchase of Dansensor:
Trade accounts receivable	(3,125,064)	967,666	(1,158,951)
Other receivables	297,177	349,008	(356,793)
Inventories	1,047,460	(356,138)	72,314
Prepaid income taxes	(158,081)	159,341	22,680
Prepaid expenses	(271,079)	(97,577)	(61,135)
Accounts payable	693,916	63,000	609,985
Compensation and related expenses	(269,619)	226,124	632,832
Other accrued expenses	(24,624)	74,854	167,022
Accrued product warranties	(55,160)	(10,000)	12,207
Accrued income taxes	(365,304)	513,614	147,113
Deferred revenue	(756,277)	133,372	138,506
Net cash provided by operating activities	521,118	8,105,188	5,225,771
Cash flows from investing activities:
Purchases of marketable securities	(365,000)	(5,841,312)	(4,897,036)
Proceeds from maturities of marketable securities	4,763,333	1,182,707	4,389,594
Purchases of property, plant and equipment	(1,637,653)	(882,061)	(1,645,628)
Cash paid for investment in affiliated company			(3,633,909)
Payment for purchase of Dansensor, net of cash acquired	(12,764,429)
Proceeds from sale of property and equipment	171,917	713	7,590
Cash paid for patent and trademark registrations	(255,916)	(230,163)	(120,659)
Other	(3,104)	(2,769)	(3,521)
Net cash used in investing activities	(10,090,852)	(5,772,885)	(5,903,569)
Cash flows from financing activities:
Proceeds from the revolving line of credit	7,452,850
Payments on the revolving line of credit	(2,200,000)
Proceeds from term note payable	3,500,000
Payments on term note payable and seller financed note payable	(3,550,768)
Payment of debt issuance costs	(45,118)
Proceeds from the exercise of stock options	421,680	1,260,598	454,124
Excess tax benefit from employee stock plans	98,210	208,067	101,830
Dividends paid	(2,271,896)	(2,104,739)	(1,952,872)
Net cash provided by (used in) financing activities	3,404,958	(636,074)	(1,396,918)
Effect of exchange rate changes on cash and cash equivalents	154,346	(225,631)	(363,163)
Net increase (decrease) in cash and cash equivalents	(6,010,430)	1,470,598	(2,437,879)
Cash and cash equivalents:
Beginning of year	8,425,846	6,955,248	9,393,127
End of year	2,415,416	8,425,846	6,955,248
Supplemental disclosures of cash flow information:
Cash paid during the year for income taxes	1,586,154	2,371,164	2,009,582
Cash paid during the year for interest	261,211	7,191
Supplemental schedule of noncash investing and financing activities:
Dividends accrued	579,386	543,881	500,235
Purchases of fixed assets and intangibles in accounts payable	188,800	923	28,162
Assets acquired under capital lease	57,379
Seller financed note payable for the acquisition of Dansensor	6,484,413
The Company purchased all of the common shares of Dansensor for $20,081,600 on April 2, 2012. The reconciliation of cash paid and liabilities assumed is as follows:
Fair value of assets acquired	26,938,817
Liabilities assumed	(6,857,217)
Net acquired assets	20,081,600
Seller financed note payable	(6,484,413)
Cash acquired	(832,758)
Payment for purchase of Dansensor, net of cash acquired and seller financed note payable	$ 12,764,429