Examples

Overview

The following examples provide a quick start on building the System Module used to control 3 HPLC pumps Knauer P4.1S. This is a typical HPLC pump that can provide a certain range of liquid flow rates and can measure the liquid pressure. The unit cannot read the actual flow – only the setpoint, but it is often sufficient.
The examples go in the order of increasing complexity.
(Example 0) If you build a system, the lowest complexity might be just opening the corresponding Device Monitors, starting them standalone and controlling the devices from several working VIs – this is a valid operation particularly suitable for quick proof-of concept tests.
Example 1 shows the most basic manual operation of 3 Knauer P4.1S pumps. The example shows how to run several Device monitors in parallel with manual control and no interlocks across the pumps.
Example 2 adds interlocks on Level 2 alarm (here overpressure in a single unit) and improves a graphical user interface
Example 3 builds on Example 2 with the automatic stepwise execution. You set a sequence of steps and the system executes them

Further, please see description of [Device Monitors].

In these examples, we took 3 pumps

You also need to download freely-avaliable Knauer instrument drivers via Labview
These MUST be connected to various RS232 ports. You may use cheap multi-port USB to RS232 adapters. Most of them are very reliable.

You cannot use daisy-chain connections here! The reason is that interconnected systems are more difficult to re-configure. If you need, you can always make a device monitor for a particular daisy-chain connection. For example, Bronkhorst mass flow controllers are assumed to be connected via a daisy chain.

Example1

Example 1 provides a quick start introduction. Here we show a minimum program to run 3 pumps in parallel with manual control on a single panel.

Please open the VI Block Diagram. It contains 3 parts: Initialisation, device monitors and User interface.
Initialisation resets all type definitions to default to avoid executing a previously pressed Stop button or some strange setpoint.
The Device monitor section simply starts the corresponding Device Monitors for 3 pumps running simultaneously. All essential features such as datalog, communication error recovery, shutdown on overpressure are provided inside the device monitor. You need to provide the (i) Communications settings, (ii) 2 references to the valid IN and OUT type definitions – the variable clusters that control and display the pump behaviour.
The User interface section simply updates the type definitions every 100 ms and stops all the pumps is the user presses the muster STOP button. Pumps may be stopped here individually if needed.

Example 2

Example 2 builds on Example 1 to provide a safety interlock and improve the user interface. It is still a fully manual operation.

The interlock stops all the pumps if either is over pressurised (L2 alarm).
The System Module VI contains segments responsible for (i) variable initialisation, (ii) starting the device monitors, (iii) operation state machine that controls and sends setpoints to units, (iv) user interface and basic interlock state machine. The Device Monitors in (ii), once started, continue working until stopped with the corresponding type definitions.

Example 3

Example 3 makes another step with autonomous operation of the pumps. You enter the sequence of steps and the VI executes them.

Further, please see description of [Device Monitors].