The 928 is a complete system for replicate measurements of dissolved oxygen, together with data recording and analysis by computer. Use of this system will result in considerable time saving in both respiration experiments and in dissolved oxygen monitoring situations. The system is comprised of a microprocessor-based interface which accepts up to six 1302 microcathode oxygen electrodes, and dedicated Windows software. All operations are controlled from the computer screen, and output of recordings in chart recorder format to a printer is available.

The interface provides the polarizing voltage to the electrodes, amplifies the low-level signals, makes the A/D conversion, and feeds the resulting data stream to the computer. The system is a “virtual instrument” therefore there are no front panel controls. All operations are controlled by the computer. An illuminated front panel display provides information on the activity of the interface and displays readings from the electrodes when they are in use.
The 928 Oxygen System may be used with the Model RC 650 6-electrode Respirometer.

Software included.
The software used in the 782 meter and the 928 system is essentially similar. The main difference is that the 928 displays up to 6 traces, while the 782 has a maximum of two.

The program has been written so that it is extremely user-friendly and quick to learn. It can be used for closed cell respirometry (with the MT200, RC300, RC350 or RC650), or flow respirometry (using the FC100 or MC100) or for monitoring dissolved oxygen (using the FC 100 or MC100). When used for respirometry experiments, it follows the familiar logical sequences of operations, from electrode calibration to recording and analysis. The program follows a sequence of 3 main stages: Setting up, Recording, and Analysis.

Setup
The setup screen is used for entering all of the details which the computer needs in order to record in the correct units, and to express the respiration rate, normalized to biomass units if required, in the desired units. All experimental details entered here are transferred through to the final calculated results report page. During setup, the cell volumes (for closed cell) and flow rate, electrode positioning (for flow respirometry), temperature of the experiment, scrolling speed of the traces during recording, and the instruction to print the recording screen to printer (if hard copy is required) are all entered. Many of these will not change from one experiment to the next, and it is only necessary to enter changes.

Recording
Clicking the ‘Start’ button initiates the recording process, and traces then scroll across the screen. If substrates, inhibitors or other solutions require to be added during the run, the position where this occurs can be recorded with a flag, and the nature of the addition is recorded on a drop down menu. At the termination of the experiment, the data are saved to a data file, and may be analyzed straight away if required.

Analysis
The data file, recorded traces, and event marker flags are recalled to the screen. If the recording has exceeded one screen width, it can be contracted to fit the screen, if required. Alternatively it is possible to scroll along long recording traces. Selector lines may be dragged to enclose specific parts of the trace. Thus if the traces show both control respiration and changed respiration after adding a solution, the selector lines would be dragged to the control rate first and then to the changed rates.
In each case respiration rates (normalized if so designated) are calculated automatically by clicking the ‘Calculate’ button. The calculated rates are tabulated, together with the experimental details entered during Setup, on the report page. The results may be exported to a spreadsheet, word processing or statistics package. The Analysis screen and the Report page may be printed, if required.

When the software is used for dissolved oxygen monitoring, the Analysis screen which displays the recorded traces and the oxygen values at flagged points or at set times can be transferred to the Results and report page.

The program requires a computer with a minimum specification of: Pentium processor, 1 free serial port, 64 Mb RAM, Windows 95 or later and 4 MB hard disk space. A comprehensive Instruction Manual is supplied, which will be particularly valuable to anyone who is not familiar with respirometric work.

This software is supplied with the 6-Channel Oxygen System Model 928 and the 1-2 Channel Oxygen Meter. It is not available separately.