I'm using a Tektronix TDS3034 4-channel oscilloscope to check a board. All channels are using P6139A 10x probes. It's triggered off channel 3, which shows a fairly clean square wave, swinging between 0V and 3.3V. Horizontal is holding steady with only a rare glitch causing some jitter. Everything looks fine so far.

Except when I use the built-in frequency measurement, I get a plausible reading, but along with the text "low signal amplitude" on the screen. If it's physically receiving 0.33 V at its input, shouldn't that be fine?

  • \$\begingroup\$ What frequency range is the signal in? If it's very low (e.g, 1 Hz), the oscilloscope may not be able to measure it properly. \$\endgroup\$ – duskwuff Feb 18 '17 at 2:06
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    \$\begingroup\$ Increase the volt/div setting maybe? A lot of scopes have the actual displayed signal closely tied to what they analyse, so if the input is big enough but small amplitude on the display, it might not work well. \$\endgroup\$ – mbrig Feb 18 '17 at 2:38
  • \$\begingroup\$ Signals are digital or PWM, 3.3V or more, with pulses rates not exceeding 100Khz, and always at least about 100Hz. \$\endgroup\$ – DarenW Feb 19 '17 at 7:49
  • \$\begingroup\$ mbrig: I'll try that, next time I'm at work, Tuesday. \$\endgroup\$ – DarenW Feb 19 '17 at 7:50

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