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I need to tap a signal on a BNC cord to record it with a Labjack ADC. The signal is very low frequency, as the FFT shows. I was planning on using an RF power splitter to add a line to the Labjack. Would an RF power splitter even be necessary for this application?

Also, I realized that the way I'd connect the labjack might negate whatever effect the splitter might have. I would probably just strip the cable and run the core to the Labjack's leads. That seems like it would throw the impedance of the whole line off making the RF splitter useless. Should I be concerned about this method of capturing my signal? Is there a better way to connect a BNC cable to a Labjack screw terminal block?

Signal FFT

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2 Answers 2

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1kHz is audio frequency range, you don't need to worry about controlled impedance or reflections. You can use a regular BNC splitter or whatever you like.

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No, you do not need to use an RF splitter for such a low frequency. However, if you were to use a splitter designed for 50Ω transmission lines with your LabJack you would not see any impact as long as both ports have a high-impedance termination (like the LabJack, oscilloscope, or most audio signal loads), it would just be an expensive BNC tee. If you were to terminate either output port in 50Ω you may lose some of your signal since you are now drawing current through the DC resistance of the divider circuit (plus the source impedance).

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  • \$\begingroup\$ I agree with your answer except for the part about losing half the signal when terminating to 50 ohms. Doesn't that make an assumption about the source impedance? \$\endgroup\$
    – crj11
    Sep 6, 2018 at 19:26
  • \$\begingroup\$ Yes, you are right. The impedance of a resistive divider at DC is not going to be 50Ω, and you have to include the unspecified source impedance. \$\endgroup\$
    – Mike
    Sep 6, 2018 at 19:44

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