If your Respiratory Belt Transducer recording displays a continuous, repeating triangle wave pattern like the following image:
this waveform is the belt’s built-in error signal. When you power on the belt, its onboard firmware checks for saved calibration settings. If that calibration data is lost or corrupted, or if the belt cannot detect a sufficient difference between being relaxed and stretched, it outputs a repeating triangle pattern instead of respiratory data. You can quickly resolve this by performing a manual recalibration to reprogram its relaxed and stretched limits.
Please note that LabChart does not need to be open or recording during this procedure, as the calibration routine runs entirely on the belt's internal sensor. However, plugging the belt into a powered PowerLab DIN port immediately initiates a strict 10-second calibration window. You must perform the physical calibration sequence immediately after connecting the belt.
To recalibrate the belt, complete the following steps:
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Prepare the belt: Disconnect the Respiratory Belt from the PowerLab DIN port and lay it completely flat, unstretched, and relaxed on a bench.
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Connect to the PowerLab: Plug the belt into the PowerLab DIN port. The internal 10-second calibration timer starts the exact moment the connector makes electrical contact.
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Wait unstretched (2 seconds): Leave the belt completely relaxed on the bench for 2 seconds. The firmware ignores the first 1.5 seconds while power stabilizes, then samples the baseline resting value.
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Stretch and hold (2 to 3 seconds): Immediately stretch the elastic band to a nominal, near-maximum point and hold it steady for 2 to 3 seconds so the firmware registers the peak stretched value.
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Release before 10 seconds: Release the belt back onto the bench so it is relaxed before the 10-second mark. At 10 seconds, the window closes, and the belt verifies the difference between the stretched and relaxed states before automatically saving the new calibration to memory.
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Power-cycle the belt: Disconnect the belt from the PowerLab DIN port and plug it back in. The belt will now boot directly into normal operation.
Once reconnected, start sampling in LabChart and pull on the belt by hand to verify that the signal tracks your movements smoothly and that the triangle wave pattern is gone. If the belt continues to output a triangle wave after repeating this timed sequence, the internal sensor may have another issue.
For further technical assistance with this or any other issue, please contact ADInstruments Technical Support by clicking HERE.