Two high-technology companies based in the Washington suburbs, one with a product already used by industry around the world and the other a purely speculative venture with hopes for development of medical devices, have sold initial offerings of common stock to investors.

The first company's offering last week was among the hottest stock sales of 1981, primarily because a Ft. Lauderdale newsletter said it appears to be "the most modestly valued new issue of the year."

That description by the publication New Issues was applied to Data Measurement Corp. of Gaithersburg, which sold 150,000 shares at $5 apiece in an offer managed by the Wachtel & Co. investment firm of Washington. Data Measurement designs, manufactures and sells electronic instruments that measure thickness and that detect pinhole flaws in the primary products produced by metals and plastics industries.

A second company to "go public" was Hemokinetics Inc., a Springfield manufacturer of medical devices that hopes to market devices that can measure and monitor body functions. Hemokinetics sold 5.5 million common shares at 60 cents a share through a syndicate headed by OTC Net Inc. of Denver, the world's current capital of penny stocks.

As with most initial sales of common stocks, prospectuses for the Data Measurement and Hemokinetics offerings emphasized a high degree of risk involved in young business ventures. The Hemokinetics stock, in particular, was described as "highly speculative."

Data Measurement began operations in 1962 as Industrial Gauging and Control Inc. Proceeds of some $580,000 from last week's stock sale will be applied to product development and engineering, sales and marketing, acquisition of production equipment and for working capital.

The company makes two types of products -- thickness gauges and pinhole detectors. Typical thickness devices measure metals as they are produced from a rolling mill. The pinhole detectors are designed to locate minute holes in tin plate, steel, titanium, copper, brass and aluminum.

Sales in 1980 totaled $2.5 million, of which 62 percent came from overseas. Manufacturers in Taiwan, West Germany, South Africa and Italy are among prime customers of the suburban Maryland firm. Overall sales last year were up from $1.17 million in 1978 and $1.45 million in 1979. Profits last year rose to $149,000 from $84,000 and, in the first six months of 1981, the company earned $76,800 on sales of $1.2 million compared with a loss of $94,400 and sales of $687,400.

New public investors own 42.9 percent of Data Measurement's 350,000 shares outstanding. Most of the firm's stock is owned by Chairman and President Dominique Gignoux, who has headed the firm since 1977. He has been active in research and development for advance technology businesses since becoming a U.S. citizen in 1960 and formerly was president and founder of Cosmic Inc. and Columbia Research Corp.

Hemokinetics is one of several operations being spun off as separate ventures by Ensco, a R&D firm in Northern Virginia. With the stock sale, public investors now own close to half of Hemokinetics class A stock and Ensco retains a major role with ownership of all class B shares (no vote for directors but one vote per share on other actions). Ensco also has agreements under which it will do research work for the new company and be paid for other services.

President Stanley Doran said Hemokinetics will focus initial activities on R&D efforts necessary to measure and monitor relative changes in blood pressure with minimal or no need for direct physical contact with the subject. Later, he hopes to work on devices to monitor pulse rates and rate of flow of blood, as well.