I measured the guralp raw outputs and the TFs using the handheld unit and an FFT analyzer.

[Setup]

The handheld unit was connected to each guralp with the same cable which is confirmed t be functional with the Yend Guralp.

The signal for Z, N, and E directions are obtained from the banana connectors on the handheld unit. Each direction has mass, low gain velocity, and high gain velocity output. The PSDs of the signals were measured with an FFT analyzer. The transfer function from the mass signal to the low/high gain signals were also measured for each direction.

The adjustment screw for the E output of the Xend does not work. I had to tilt the Xend Guralp using the leg screws to bring the E signal to zero.

[Result]

Attachment 1: Raw voltage PSD for all outputs
Attachment 2: Comparison of the low gain vel outputs

- All of the mass output show similar PSDs.
- Low gain velocity outputs shows somewhat similar levels. I still need to check if the output is really the ground velocity or not.
- High gain velocity outputs are either not high gain, broken, or not implemented.

- We need to calibrate the low gain output using signal injection, huddle test, or something else.

Attachment 3: TFs between each mass output and the low or high gain outputs

- TFs between the mass signal and the low vel signals show the similar transfer functions between the channels.
- The high gain outputs show low or no transfer function with regard to the mass signals.