I"ll start by saying I'm not an EE nor any engineer for that matter, if you couldn't tell from the question.
We take a Chinese made Lab peristaltic pump and modify it to be used in the Operating Room for a medical procedure. Don't worry it is harmless and non-critical, so no one is getting sued. Previously the same pump passed the 3rd ed of the 60601-1-2 testing but failed the 4th ed, when it got to the Immunity testing specifically 385 MHz and 450 MHz testing. We did some more modifications, Added a second LED module, which meant a new LED board built and added a stacker board to the PCB that was in the machine already to bypass most of it's functions. All the main board does is run the stepper motor now. We also added a UL listed, medical approved Power supply to help get FDA and CE approval. The two frequencies above would interrupt the machines function and sometimes stopping it altogether, but never killed it outright. We have tried some shielding and ferrite beads on a long Ribbon cable (18") which helped. The Ribbon cable goes from teh LED bd in the case, which is plastic, to the Stacker bd on the main PC bd. We were using a hand-held transmitter, like a walkie-talkie to test it with in house. We sent it back and their first test at 385 MHz killed it and couldn't get it restarted. That's never happened before.
My question is: "What do these frequencies do to the machine to damage it in this way? And could we have damaged it here with our crude testing?
It worked fine when we returned it to the testing facility. The output of our transmitter was 5w with an omni-direction antenna (looked like a walkie-talkie). Their test was done at like 2.5w with a directional antenna (Table 9 from the 60601-1-2 regs). What do I look for in the way of damage?
We take a Chinese made Lab peristaltic pump and modify it to be used in the Operating Room for a medical procedure. Don't worry it is harmless and non-critical, so no one is getting sued. Previously the same pump passed the 3rd ed of the 60601-1-2 testing but failed the 4th ed, when it got to the Immunity testing specifically 385 MHz and 450 MHz testing. We did some more modifications, Added a second LED module, which meant a new LED board built and added a stacker board to the PCB that was in the machine already to bypass most of it's functions. All the main board does is run the stepper motor now. We also added a UL listed, medical approved Power supply to help get FDA and CE approval. The two frequencies above would interrupt the machines function and sometimes stopping it altogether, but never killed it outright. We have tried some shielding and ferrite beads on a long Ribbon cable (18") which helped. The Ribbon cable goes from teh LED bd in the case, which is plastic, to the Stacker bd on the main PC bd. We were using a hand-held transmitter, like a walkie-talkie to test it with in house. We sent it back and their first test at 385 MHz killed it and couldn't get it restarted. That's never happened before.
My question is: "What do these frequencies do to the machine to damage it in this way? And could we have damaged it here with our crude testing?
It worked fine when we returned it to the testing facility. The output of our transmitter was 5w with an omni-direction antenna (looked like a walkie-talkie). Their test was done at like 2.5w with a directional antenna (Table 9 from the 60601-1-2 regs). What do I look for in the way of damage?
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