How to perform a Scale Factor calibration

Step 1. Place the paddle onto the calibration rig (right blade)

  • Place the paddle with the right blade against the end plate (if using the calibration rig) or with the right blade on to the close (blade) support.

  • The blade should ideally be supported near its center and the shaft support should be approximately at the top hand position.

Step 2. Record the zero-load outputs

  • With the paddle in position, but without any load applied, open the Calibration page of the Web Bluetooth app and record the relevant* strain outputs and relevant orientation angle in the first row of the Scale Factor spreadsheet.

*A & B when the right blade is against the end plate and C & D when the left blade is against the end plate.

Step 3. Apply load to the shaft

  • Place the load hook onto the shaft (if using the calibration rig) or place a bucket tied to the shaft with a short piece of rope.

  • Hang a weight off the load hook (if using the calibration rig) or place a weight into the bucket.

  • Record the relevant* strain outputs and relevant orientation angle in the second row of the spreadsheet.

  • Enter the mass of the applied weight into the spreadsheet. Don't forget to include the weight of the load hook (if using the calibration rig) or the weight of the bucket and rope.

*A & B when the right blade is against the end plate and C & D when the left blade is against the end plate.

  • Repeat this step for each point in the calibration process and record the relevant strain output, orientation and mass of the applied weight in the corresponding row.

The spreadsheet allows for 2, 4 or 6 point calibrations. Ensure the position of the applied load; the close support and the far support remain the same for each 'point'.

Step 4. Measure and enter the tip to supports and tip to load locations

  • Tip to Close Support:

    • The distance from the blade tip* to the close (blade) support.

  • Tip to Far Support:

    • The distance from the blade tip* to the far (shaft) support.

  • Tip to Applied Load:

    • The distance from the blade tip* to the load hook / position where the load is being applied.

* this is the end plate (if using the calibration rig) or the blade tip of the blade laying on the close support

Step 5. Remove the weights and load hook

Step 6. Measure and enter the tip to datum location

  • Remove the paddle from the rig and measure the distance from the blade tip that had been placed against the end plate (if using the calibration rig) or from the blade tip of the blade that had been laying on the close support to the datum mark on the same shaft (i.e. left blade tip to datum on left shaft or right blade tip to datum on right shaft).

  • Enter this measurement into the spreadsheet.

Step 7. Enter the datum to channel distances

  • The datum to blade channel and datum to centre channel distances can be read from the shaft using the Advanced page of the Web Bluetooth app.

  • Enter these values into the calibration spreadsheet.

Step 8. Place the paddle onto the calibration rig (left blade)

  • Place the paddle with the left hand blade against the end plate.

  • The blade should ideally be supported near its center and the shaft support should be approximately at the top hand position.

  • Repeat Step 2, Step 3, Step 4, Step 5 & Step 6.

Step 9. Retrieve the Scale Factors from the spreadsheet

  • The Scale Factors for each channel will be shown in the corresponding plot.

e.g. y = 0.1747x indicates the Scale Factor is 0.175

Step 10. Navigate to the Calibration page of the Web Bluetooth app and connect to the power meter

Step 11. Click on each row of the table to enter the corresponding Scale Factor for that channel

  • The Scale Factors should be multiplied by 1000 before being entered into the app. For example, if the Scale Factor is 0.1747, then the value '175' should be entered into the app. This value has been rounded up to three significant figures and does not include any decimal places.

The scale factor 0.1747 is entered in as 175.