The Power Switching Module PSM-420 is a safety switch, wich is linked with solvent level monitoring. In case of a critical event such as a full waste the PSM-420 is triggered to a controlled power shutdown.
The PSM-420 has 4 power outputs. Each of them can be switched on or off manually. An LED shows the status of each channel.
The PSM-420 has 3 power shutdown schemes depending on the type of event. They can be activated by dip switches on the front side panel of the instrument:
Timer Waste ON: In case of a full waste the power shutdown is delayed
Timer Eluents ON: In case of an empty eluent the power shudown is delayed
Software response ON: This watch dog function is asking a signal (contact closure) within the timer duration, otherwise a power shutdown is triggered.
General alarm: This function is always active and cannot be switched off. A leak detection signal e.g. can be connected to this input.
Each timer duration can be configured via a terminal program on a pc.
Two redundant interfaces (DB25) are available for digital signal input. Each input can be configured as an opening (NC) or a closing (NO) contact, respectively.
The watch dog function is useful to monitor the correct mode of operation of a control software as e.g. for a preparative HPLC system when it is running in unattended mode. In case of a crash of the computer program the continuous reset signal would also stop which then trigges a power shutdown to stop the pumps.