is there any risk using line-out as a source for DAQ?

[r0r0s]

for a class on LabView programming i made an assignment where students

used a sine-generator on their pc to output the signal through their headphone jack
and into the analog input of a USB-6002.

One student i saying this setup broke the audio port of his laptop.
Is this possible and if so how do i safeguard againt such accidents in the future?

many thanks,

Rory

[muhammad.kamran.ayub]

Hello Rory,

This depends on multiple things and is quite subjective from laptop to laptop. 

1. What was the maximum voltage limit of the headphone port? Was it violated during experimentation? Ideally, there should be voltage limiters in the background. <https://superuser.com/questions/718466/what-is-typical-notebook-laptop-headphone-jack-power-rating>

2. Normally, a speaker has an impedance of 8Ohm while NI USB-6002 has >1Gohm AI impedance. This is not crucial if the frequencies are pretty low. However, there are reflections when the frequency is increased. Audible frequencies should not be that vulnerable to damage port. Can you please let me know the frequencies?

Thanks

Best Regards,
________________________________________
Muhammad Kamran Ayub
Staff Technical Support Engineer | Platforms & Systems
Certified LabVIEW Architect (CLA) | Certified TestStand Developer (CTD)
National Instruments UK & Ireland

[muhammad.kamran.ayub]

Hello Rory,

Do we have any progress on this issue?

-Kamran

[r0r0s]

Hello Kamran,

1. it's hard to reconstruct the situation as i wasn't part of the lesson where this occured.
Im trying to get more specific information from the student. 

When you say voltage limiters should be present do you mean in the laptop or on my circuitboard?

2 would a parrallel 80 Ohm resistor solve the possible reflection issue or possible create new ones?

thanks for the help,

Rory Dijkink

[muhammad.kamran.ayub]

Hey Rory,

1. I would imagine the voltage limiters to be part of the laptop's circuitry before the audio jack. Though, I am not sure. The student can check with his Laptop vendor. But, you can implement soft voltage limiters on LabVIEW to be sure that the voltage level does not exceed safe limits. The definition of the 'Safe Limits' might vary from laptop to laptop, but I am sure that you can figure out a min value safe for all devices.

2. The impedance mismatch and reflections are not hazarding for lower frequencies, but yes, for higher frequencies. To avoid them, there needs to be impedance matching between source and sink. There are various impedance matching circuitries you can find if you want to use, but I think this will be extra effort, esp. when we can live with lower frequencies for demo purposes.

Please let me know if you need any additional help or accept the response as an answer.

Thanks

-Kamran

[muhammad.kamran.ayub]

Hey Rory,

Please let me know if you need any additional help?

Thanks

-Kamran