Pump and Flow Control
Setting Automatic Pre-Compression Control (P580)

The better the pump is set to the varying compressibility of the different components of the solvents, the lower the pump's pulsation. Automatic pre-compression control of the Dionex P580 pump considers the varying compressibility of different solvents. Automatic pre-compression control can also be used for unknown solvents.

With low-pressure gradients and isocratic pumps, pre-compression control is fully automatic. On the Control Panel, select Commands on the Control menu. Select the pump and the solvent components one after the other and assign the component type Automatic.

The high-pressure gradient pumps must "learn" the automatic pre-compression control. Select Commands on the Control menu. Select the pump and the solvent component. Assign the solvent type Custom. Deliver 100% of this solvent at 1 ml/min and a backpressure of approximately 100 bar (= 10 MPa = 1450 psi). Select Commands on the Control menu and issue the Learn command. Observe the pressure signal for at least 10 minutes. Issue the corresponding pump Freeze command to save the optimum pre-compression setting when the pressure fluctuations from the pump are minimal.

 Tip: 

During the Learn phase, the backpressure should correspond to the maximum pressure in normal operation. If the backpressure is less than 25°bar (= 2.5 MPa = 362.5 psi) during this phase, pre-compression control cannot be set correctly! Increase the backpressure, for example, by installing a second column or a longer capillary before the detector. Again, wait for approximately 10 minutes before saving the pre-compression value using the Freeze command.

Change the flow to 100% of the next solvent and set the pre-compression control as described above.

For a detailed description, refer to the P580 Operating Instructions.