The FlexStream is composed of one or more of the following modules, depending on application requirements:
- FlexStream Base module (shown above and below): The 'Base' module is required in every FlexStream system. This module provides (a) front panel color touchscreen, (b) permeation tube oven, (c) primary dilution mass flow rate and (d) Ethernet and serial RS-232 connectivity to an external computer.
- FlexStream Auxiliary Permeation Oven Module (PM) (shown below): Additional permeation tube ovens allow generation of a multi-component gas stream for cases in which (a) the tubes must be maintained at different temperatures, (b) differing permeation technologies (disposable tubes vs. refillable tubes) are required, (c) more components are needed than can be held in a single oven, or (d) for applications in which various components will be switched in and out of the gas stream. Up to 5 PM oven modules can be added wherein each oven can hold up to eight disposable permeation tubes or one factory-refillable tube. An added benefit is that any combination of ovens can be kept on standby to keep various tubes at temperature while not adding their emission to the output gas stream.
- FlexStream Gas Feed Permeation Oven Module (GF) (not shown): Most applications can use liquid-filled permeation tubes. However, some compounds (e.g., NO, CO, O2, etc.) have very high vapor pressures and require a special mechanism to achieve desired concentration levels. The Gas Feed Module contains the same oven as an auxiliary Permeation Oven Module (PM) but with additional controls that allow the customer to refill a 'customer-refillable' gas-fed permeation tube and to set the operating pressure of the tube. These are special tubes, typically made of stainless steel. Prior to shipment, KIN-TEK determines the tube membrane's certified emission rate for one or more components. In use, the customer typically supplies component gas from a cylinder to initially fill the tube and to periodically recharge it.
- FlexStream Secondary Dilution module (SD) (shown below): The SD module extends the range of concentration attained from permeation tubes by providing an additional stage of dilution of the gas stream. Very low concentrations - ppb or ppt - can be generated depending on the emission rate of the tubes and the flow rate range of the primary and secondary dilution mass flow controllers. Overall dilution ratios of 10,000:1 can be achieved.
- FlexStream Interface Module (IM) (not shown): The Interface Module contains gas stream interfacing components needed to assure constant gas stream output conditions independent of variations in flow and pressure. The Interface Module is ideal for applications where flow capacity of end use 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. Controls are provided on the front panel for adjusting the output pressure.
- FlexStream Modular Gas Standards Generator (shown below): The FlexStream Base module and any additional modules can be packaged in stand-alone carrying cases or packaged in one or two 3-module expansion cases as shown below (unused module slots in the expansion case are filled with blank panels). The modules are electronically connected to each other by a short cable on the rear panel.
KIN-TEK supplies a Windows® executable program named “FlexLink™” to monitor and control the generation of multi-component concentrations with the FlexStream™ gas standards generator. The FlexLink program is provided on CD with shipment of each FlexStream instrument. (Note: FlexLink is not required in order to operate the FlexStream instrument.)
FlexLink communicates with the FlexStream using the industry standard Modbus RTU protocol over serial (RS-232) and/or Ethernet (TCP/IP) physical interfaces. FlexLink can also interface to RS-485 with addition of an RS-232 to RS-485 converter (not supplied).
The program continually reads data from the FlexStream, presents the data in various indicators on the PC computer, and allows the user, via the PC, to control the standby, zero and span functions of the FlexStream. Additional functions include viewing the FlexStream configuration, setting oven temperature setpoints and alarm limits, uploading and downloading permeation tube properties to/from the FlexStream and logging acquired data to files.
An added benefit of using Ethernet (TCP/IP) is that the FlexLink program can be run in another room, or even off site, for applications in which the operator needs to be removed from the gas standard generation function. Plus, while one PC may be controlling the FlexStream locally with an RS-232 serial link, another PC may be monitoring the FlexStream remotely via the Ethernet link.
In Figure 1, a target concentration of 1 ppm has been requested. Figure 2 shows the actual generated concentration results for eight permeation tubes that have been loaded into the FlexStream Base module. Figure 3 shows the logged data results.