It sounds like an issue with the calibration of the open and close position. I would calibrate the positions for two reasons:

1. When clamping the leaf and waiting for an extended period of time before running the protocol, you might perturb steady state photosynthesis, which might causes a less accurate measurement of the photosynthetic parameters
2. You save a lot of time when doing large scale experiments

Hello Sebastian Would you please send me calibration of the open and close position. Either we need to do as follow or something else 1- Connect the device with Desktop application 2- Click on setting Tab..... A pop up window open with three Tab 3- Click on Instrument Settings Tab (central One) 4- Make the Clamp Open .... 5- Press the button Set ---- Clamp Position Open 6 - Close the Clamp while placing leaf.... 7- Press the button Set ... Clamp Position

Please follow these instructions as discussed here.

1. Open the Desktop App and connect your Instrument
2. Select View->Console from the menu to open the console
3. Use the command set_open_closed_positions followed by enter
4. You get asked to set the open position = 4mm and closed position = 2mm
5. Use + followed by enter after each position.

~Sebastian