Configuring the Sampling Sequence block

This section will cover the steps needed to configure the elements under the Sampling Sequence block. If you have just opened the Configuration page, you will see two empty parent blocks: the LI-8250 Multiplexer block and the Sampling Sequence block. It may be helpful to first configure the physical components under the LI-8250 Multiplexer block before configuring your Sampling Sequence. See Configuring the LI-8250 Multiplexer block.

The Sampling Sequence has three different events that can be added: Observation, Delay, and Disable Sampling Pumps. Each block added will update the Total Estimated Duration of the sequence which must be taken into consideration when choosing when to start the sequence.

The Sampling Sequence runs in sequential order from top to bottom and completes when it reaches the bottom.

Tip: When configuring a system with multiple chambers and extension manifolds, you can copy/paste or duplicate blocks to speed things up (see Workspace actions).

1. Choose when to start the sequence

The Start Sequence in the Sampling Sequence block defines when the LI-8250 Multiplexer will begin its sequence after you click Start on the Home page.

• Continuous Sampling will immediately start the sequence, run through all events, and will begin again once finished.
• 15 [min] starts the sequence on the next quarter-hour. For example, if you set the Start Sequence to 15 [min] and click Start at 12:07 AM, the sequence would begin at 12:15 AM.
• 30 [min] starts the sequence on the next half-hour. For example, if you set the Start Sequence to 30 [min] and click Start at 12:07 AM, the sequence would begin at 12:30 AM.
• 1 [hr] starts the sequence on the next hour. For example, if you set the Start Sequence to 1 [hr] and click Start at 12:07 AM, the sequence would begin at 1:00 AM.
• 2 [hr] starts the sequence on a 2-hour interval from midnight. For example, if you set the Start Sequence to 2 [hr] and click Start at 12:07 AM, the sequence would begin at 2:00 AM.
• 4 [hr] starts the sequence on a 4-hour interval from midnight.
• 6 [hr] starts the sequence on a 6-hour interval from midnight.
• 12 [hr] starts the sequence on a 12-hour interval from midnight.
• Daily will start the sequence at midnight of each day.

2. Set behavior after a disruption

In the event the system experiences a disruption, such as a power outage, you can define how the Sampling Sequence will behave when it comes back online through the On Disruption field.

• Beginning will restart the Sampling Sequence over from the beginning.
• Next tells the LI-8250 Multiplexer to see where it was in the Sampling Sequence and start from the next event.
• As Expected will cause the LI-8250 Multiplexer to assess the length of the disruption and to pick up where it should be at in the Sampling Sequence.

3. Add an observation

An Observation includes all the time that a port is selected and active, including purges and measurement. Adding an Observation block to the Sampling Sequence block tells the multiplexer to perform an observation on a specified port. Several observations can be strung together for a single port or multiple ports. Each observation Duration is determined by the combined Pre-Purge, Post-Purge, and Observation Length for the chamber on that port.

To add an Observation to the Sampling Sequence, select Sampling Sequence from the Toolbox. Then click and drag an Observation block to where you would like it placed in the sequence.

4. Set the port

Setting the port tells the multiplexer which chamber should be active during the observation. Adding an Observation block automatically includes a Multiplexer Port # block. To begin, change the Multiplexer Port # to the port you would like to observe in this Observation.

If you do not have an 8250-01 Extension Manifold, you can skip to step 5. If your system does include chambers connected to one or more extension manifolds, then you will need to add an Extension Manifold Port # block.

To add an Extension Manifold Port # block, select Sampling Sequence from the Toolbox, then click and drag an Extension Manifold Port # block and connect it to a Multiplexer Port # block. Verify that the port number set on the Multiplexer Port # block has an extension manifold physically connected to it.

5. Add a delay

Delay is simply a pause in the Sampling Sequence. You can place a Delay wherever it is needed, for as long as is needed. To add a Delay , select Sampling Sequence from the Toolbox, then click and drag a Delay block to where you would like to add the Delay in your sequence.

Then set the Duration and Unit to suit the length of Delay you would like.

Two observations on a single port with a 2-minute delay between observations would appear as such.

6. Disable sampling pumps

There may be times where you will want to disable the sampling pumps. This would typically be during an extended Delay where you would not want the pump running the entire time. Disabling the pumps is less noisy and preserves the life of your pumps. A Disable Sampling Pumps block should appear immediately before a Delay block.

To add a Disable Sampling Pumps block, select Sampling Sequence from the Toolbox, then click and drag the Disable Sampling Pumps block before the Delay block that needs the pumps disabled.

So, if you wanted to disable the pumps during a 2-minute delay between observations, this is how you would do that.

Note: Although the Disable Sampling Pumps block only shows a Duration of 3 seconds, the pumps will be disabled for the entire Duration of the following Delay block.