Papabravo said:
What makes you think he is a hobbyist?
First off, let me apologize to anyone who was insulted by the term, "hobbyist." To me, it differentiates avocation from vocation. I often refer to myself in that way in areas in which I am not specifically employed, but nevertheless consider myself the most competent person available at the time. Similarly, I consider "fix-it man" as a compliment rather than an insult.
But, specifically to your question, the poster (mghtt84) used these phrases: ".... i'm still looking for a designed circuit ... if u or anyone knows the circuit could u pass it over and i'll be really grateful .....;" and "..... so i need a hardware design which i believe its already exist."
Those statements struck me being more typical of what I would expect from someone who was not particularly familiar with the hurdles, including IP issues, of getting a medical device to market, particularly for a large manufacturer, than from someone who was a development engineer for such a firm.
That could be wrong, but no harm was intended. Since the poster's purpose apparently has to do with performance validation, let me add just a little more to my comment about internal controls and the importance of having a trained technologist/technician. Individuals who are familiar with statistical quality control, but unfamiliar with diagnostic medicine, often make assumptions about how controls should be used to ensure quality. Some of those assumptions, unfortunately, have become law in the USA and have resulted in enormous costs with no measurable benefit. The truth is, I would put my faith in the opinion of a good technologist/technician about whether a test batch was bad rather than in an artifical control. The most common cause of a control failure, by far, is a faulty control. Clearly, if a control fails, one has to take corrective action. In my experience, however, when a tech feels that a test is unreliable, even when the controls seem okay, there is probably a problem with the test.
John