??? 12/13/05 13:39 Read: times |
#105137 - Again safety Responding to: ???'s previous message |
Mehdi said:
Analog Device said:
The AD7715 is a complete analog front end for low frequency measurement applications. The part can accept low level input signals directly from a transducer and outputs a serial digital word. It employs a sigma-delta conversion technique to realize up to 16 bits of no missing codes performance... Yes, that sounds very nice. But this is the performance which can be obtained when no additonal error sources must be taken into consideration. But in your application there are some. From your picture of board I guess, that only a doubled sided board is used, not at all supporting the concept of solid ground plane. This is absolutely deadly in combination with a 16bit ADC. May be not on your warm and bright desk, where everything runs fine, but in real application, when ESD and interference tries to sabotage your application from all directions. Do you use proper low pass filtering for sensor signals, for supply of ADC. How do you handle ESD at sensor lines? Do you have proper mains line filtering? MOC3063 doesn't like fast spikes very much... By the way, what we very carefully tried to tell you refering to safety, because we didn't want to offend you, is: What you do is illegal, unless you really take care, that very highest safety standards are fullfilled!!! In Germany you are not allowed to manufacture and sell life support applictaions unless you fullfill lots of very expensive reliability and safety approvals! You need to have a registered contact person to the Ministery of Health, how must be 24h a day in reach, if something goes wrong with your application. You are only allowed to put safety approved components into your circuit. etc. etc. Building a medical device here in Germany is extremely difficult, time consuming and expensive. And pray to God, if someone gets hurted or killed by what you have constructed... Here in Germany you go into prison if something was wrong with your application and you was partially responsible for it. As Erik already mentioned in detail, even when having constructed a perfet device for controlling of skin temperature of baby, you need double safety! If there's something wrong with your device, then a second, totally independent system must invoke a safe mode. Kai |