AutoBlend™ Gas Standards Generator

The AutoBlend™ [brochure] is an integrated computer-controlled gas blending system designed to create flowing, adjustable-concentration complex gas mixtures and test atmospheres. The system introduces precisely controlled trace concentration components into a flowing, high purity matrix gas.

The AutoBlend uses KIN-TEK Trace Source™ disposable, refillable and diffusion permeation tubes for over 500 chemicals.

The AutoBlend has six permeation tube ovens. Each oven can generate its component concentrations independent of the other ovens.  This is an extremely powerful feature for dynamically testing the effects of a wide range of vapor contaminants since each oven can be switched in (span) and out (vent), and the concentrations generated by each spanning oven are independent of the concentrations generated by the other spanning ovens.

AutoBlend™ Instrument

The base gas mixture created in each oven can contain up to eight different analyte components so that a test atmosphere can be spiked with up to 48 components simultaneously.

A small flow of pure dilution gas passes over the permeation (or diffusion) tubes installed in each oven to form a base gas mixture.  A variable portion of each base gas mixture is then added to a main dilution flow to create a primary mixture with variable concentration ratios.

A secondary dilution feature provides a large dynamic concentration range.  Secondary dilution is used or bypassed automatically in the system as required to produce target concentrations.

In many applications normally innocuous contaminants that occur routinely, or randomly, may be significant for testing purposes.  In the AutoBlend™, two optional dynamic headspace saturation modules can be added (as shown in bottom cabinet above) to allow the addition of vapors from potential transient interfering compounds such as cleaning solutions, fuels or paints.  Output from the headspace modules can be added either before or after secondary dilution of the trace components.

The resulting test atmosphere can be supplied either dry or at variable humidity levels with the optional humidification module.  Humidity is added by splitting the total dilution flow into two parts.  One part remains dry and contains all of the trace components from the permeation tubes and headspace modules.  The other portion of the dilution gas is saturated with water vapor.  The two portions are combined at the output of the system to form the humidified mixture.  Relative humidity (RH) is varied by varying the ratio of humidified diluent to dry diluent. The trace components do not contact liquid water in the system.

Hardware is included to assure constant gas stream output conditions independent of variations in flow and pressure. This is particulary important for applications where flow capacity is limited (e.g., filling of gas bags), or when back pressure is required to introduce the output gas stream sample to the device under test at an elevated pressure. Controls are provided on the front panel for adjusting the output pressure.

Please scroll up and click the "Software", "Applications" and "Specifications" tabs above to see more features and specifications of the AutoBlend.

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.
  
  

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.

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
  
  

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.

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.

Typical AutoBlend™ applications include:

• Sensor response evaluation to various combination of gases
• Catalyst research
• Inhalation toxicology
• Fuel cell development
• Analytical methods development
• Chemical effects testing
• Creating complex test atmospheres.

Evaluating Sensor Response

Chemical sensor systems are typically designed to give rapid indication of the concentration or change of a hazardous substance in a normally safe background.  Often, however, many innocuous and possibly interfering compounds are also routinely or transiently present.  For example, DEET-based mosquito repellant commonly used in an outdoor location might result in false positive toxic gas alarms. Or the presence of a safe compound might suppress response to a hazardous compound. Often, sensors either respond to atmospheric humidity, or their response is affected by humidity.  Identifying and quantifying such interactions is critical to qualifying a sensor system for use in a specific application.

Catalyst Research

In catalyst research and development it is important to define and quantify the effects of reactant impurities and combinations of impurities on yield and catalyst life.  The AutoBlend system’s ability to vary relative concentrations of the components can dramatically reduce testing time. It facilitates discovery of synergistic effects and is ideal for executing statistically designed vapor testing programs.

Inhalation Toxicology

The AutoBlend, with its capability to give varying ratios between components, coupled with its integral variable humidity source and the adjustable headspace vapor modules, is an extremely versatile source of test atmosphere for inhalation toxicology studies.  The system is simple to set up for a wide range compounds.  It can give concentrations from hundreds of ppm down to low ppb, and mix them into humidified air also containing various common and normally innocuous atmospheric contaminants.

Fuel Cell Development

Fuel cells offer an opportunity for direct, or near direct conversion of chemical compounds to electrical energy with minimal environmental pollution.  Success of these efforts requires development of robust catalytic systems, and thus an intimate knowledge of the long-term effects of various fuel and air (or other oxidant) contaminants.  The AutoBlend system is an excellent source for long term testing of fuel cell systems known concentration conditions.

Validating Analytical Methods

Effective analytical methods must work equally well in any laboratory setting and with a wide range of variation of reagent and/or matrix composition.  The flexibility of the AutoBlend system allows for rapid and thorough evaluation analytical methods.  A clear understanding of the method and significant parameters is essential to establishing standard methods.

Chemical Effects Testing

A chemical environment can have varying effects on a device under test based on interaction among the chemicals as well as the device. With the six independent permeation tube ovens of the AutoBlend (and up to 8 chemicals per oven), plus the optional dual headspace and humidification capabilities, a complex method can be setup in which some component concentrations are generated for the current test point, followed by different sets of chemical concentrations in the following test points. Each point of the method allows for a "run time" before automatically advancing to the next point. "Zero" points can be inserted to clear the test atmosphere at appropriate times.

Creating Complex Test Atmospheres

All of the above applications are examples of creating complex test atmospheres.

 

Principle of Operation	AutoBlend™
Delivery of precise, adjustable, low concentration dynamically blended      gas mixtures. Trace concentrations - ppmv, ppbv, pptv
Primary dilution of constant component vapor emission from permeation or      diffusion tubes. Secondary dilution is automatically added but only if needed to      bring the target concentrations to specified values
Method-driven. Up to 20 points of multi-component concentration mixtures      can be added to a user-named method.
Permeation Tube Oven
Six independent high thermal mass ovens with electronic PID control	Vertical orientation
Oven temperature range (heat only)	30-150 °C
NIST-traceable oven temperature
Oven setpoint resolution and control	±0.1 °C
Split flow mass flow controller with each oven	10 to 200 sccm
Independent oven over-temperature alarms
Diluent Gas (customer-supplied)
Uses inert, non-reactive, non-hazardous dry gas (Nitrogen, zero air,      Argon, etc.)
Mass flow meter subsystem is factory-calibrated in Nitrogen; contact factory      for calibration in other type gas
Primary Dilution Mass Flow Subsystem
Primary dilution flow rate auto-set in software as a function of target concentration
Primary dilution mass flow controller range	0.5 to 10 lpm
Mass flow rate accuracy	±1% FS
Mass flow rate indication via PC computer screen (with AutoBlend software)
Secondary Dilution Mass Flow Subsystem
Secondary dilution flow rate auto-set in software as a function of target concentration
Secondary dilution mass flow controller range	0.5 to 10 lpm
Secondary component split flow mass flow controller range	10 to 200 sccm
Mass flow rate accuracy (dilution and component flow controllers)	±1% FS
Mass flow rate indication via PC computer screen (with AutoBlend software)
Overall output gas stream dilution ratio with both primary and secondary dilution	10,000:1
Accepts Vapor Emissions from the Following Devices*
Liquid-filled disposable tubes up to 15 cm in length (maximum of 8 tubes)
Liquid-filled high rate (LFH) permeation tubes (maximum of 1 tube)
Factory pre-filled gas-fed permeation tubes (maximum of 1 tube)
Diffusion tubes (maximum of 4 tubes)
Headspace (for up to two optionally installed headspace modules only)
*Note: A single oven can hold only one of the above tube types at a time
Standard Component Flow Path
Component contacts only glass, Teflon® and stainless steel
Glass permeation tube holder
Suitable for reactive component gases
Optional Component Flow Path (specified at time of order)
Heated output lines
Stainless steel
Electro-polished stainless steel
Sulfinert-coated stainless steel
Teflon only
Teflon permeation tube holder
Standard Modes of Operation
Standby (oven venting at approx 75 to 100 cc/min flow rate)
Zero (with user-specified flow rate)
Span-by-concentration. Oven and headspace module split flow controllers,      primary and secondary dilution flow controllers and the secondary component      split flow controller are automatically set by the software in order to achieve      the target concentrations.
Output Concentration Range
Below 1 ppb to over 1000 ppm depending on tube emission rate      and primary and secondary dilution flow rates
Expandability (specify options when ordering)
Dual headspace module option (each with 200 sccm split mass flow controller)
Humidified gas module option (with 10 lpm mass flow controller)
Power Requirements (specified when ordering)
115 VAC, 50/60 Hz
230 VAC, 50/60 Hz
Speciality Applications (Please contact the Factory)
Special diluent (carrier) gases other than inert gases
Trace moisture
Chemical compatibility issues
Heat tracing requirements
Other