The Windows-hosted AutoBlend software:

  • Manages an inventory of methods, permeation tubes and optional headspace mixtures.
  • Analyzes the feasibility of creating a specified mixture.
  • Calculates the setpoint data required to adjust the system to achieve the mixture. 
  • Dynamically maintains the mixture under changing conditions.
  • Logs operating data and test mixture results.
Figure 1: Virtual instrument view of the AutoBlend system

Permeation Tube and Headspace Inventory Management

The AutoBlend software contains a database of the user's permeation tube and optional headspace inventory including tube ID and serial number, compound name, emission rate data, temperature alarm criteria, and expiration date (see below). As the expiration date approaches, the tube is highlighted to warn the user to reorder or recertify.
The following figure shows an example inventory of permeation tubes.

Figure 2: Permeation tube inventory

Method Inventory Management

As specific complex gas mixture sets are defined, the details of the components (permeation tubes and headspaces) and required concentrations of up to 20 span points are saved as a method. These methods are saved in an inventory for easy recall and duplication of the mixture at a later date. 
The figure below shows an example method setup in which three permeation ovens (PM-1, PM-4 and PM-6) are to be used. The method consists of 9 points composed of a combination of zero and span functions. Point 2 (highlighted) is a "span" point with the following configuration:

  • Oven PM-1 has multiple components (not all shown), with a target concentration of 200 ppbv for Methanol.
  • PM-4 has a water tube with target concentration of 30 ppbv and is not used for this point ("use" is unchecked)
  • PM-6 has an H2S tube with target concentration set at 1 ppmv and is on standby (vented).
  • Headspace modules HM-1 and HM-2 are not used in this method
  • Humidification is not checked; thus not used for this point
  • Span run time is set to 20 minutes for this point
Figure 3: Span point example

The above figure illustrates the AutoBlend's flexibility in generating complex test atmospheres by varying the chemical composition and humidity levels within each point of a method. Experiments can be easily setup to evaluate the effects of various combinations of chemicals on a device under test.

Data Logging

During a method run, the AutoBlend software periodically logs generated concentrations for each point in the method (see Fig. 3) and logs measured values of all operating parameters. Should an unexpected test result occur, the historical data can be checked to verify the mixture and operating conditions such as oven temperature, flow rates, pressures and so forth.

Figure 4: AutoBlend data log

Scenario Analysis

The AutoBlend software set includes a "Scenario Analyzer" CD that allows the user to establish offline the feasibility of achieving a desired mixture. Given desired concentrations, the AutoBlend software tests the possibility of creating the mixture from specific permeation tubes and headspaces under specific operating conditions. This feedback is invaluable in creating a workable method and can be a major time saver.

System Monitoring

AutoBlend system functions are monitored in the software and out-of-specification values are reported. For example, the software warns of  "over temperature" conditions in the permeation ovens, impossible flow settings, out of range temperature setpoints (for the installed permeation tubes), etc. 

Enhanced Functionality

The actual permeation rate from each tube varies with temperature. The AutoBlend software can correct to actual or estimated temperature depending on supporting data available for the tube. When multi-point certification data is available, the correction is exact at the temperature of the defined certification point, and estimated with a linear or log-linear algorithm when at an uncertified temperature point. Even for a single-point certification, an enhanced estimation algorithm is applied for the case in which the user elects to use a temperature other than the certification temperature.  

System Requirements

The AutoBlend software runs on Microsoft Windows with an RS-232 serial port (or USB-to-RS232 adapter) connected to the AutoBlend instrument. The AutoBlend Inventory and data logs are stored in a Microsoft Access database (Microsoft Access is not required to be installed). The software requires about 15 MB of hard disk space plus extra storage space for the database.