Teledyne 7300A manual Manual Mode Zeroing, Cell Failure

4 Operation Model 7300A

4.4.1.2Manual Mode Zeroing

Scroll to Zero and enter the Zero function. The screen that appears allows you to select between automatic or manual zero calibration. Use the UP/DOWN keys to toggle between AUTO and MAN zero settling. Stop when MANUAL appears, blinking, on the display.

Select zero mode: MANUAL

Enter to begin the zero calibration. After a few seconds the first of three zeroing screens appears. The number in the upper left hand corner is the first- stage zero offset. The microprocessor samples the output at a predetermined rate.

####.##	%	CO2
Zero adj:2048		C—Zero

The analyzer goes through C–Zero, F–Zero, and S–Zero. During C–Zero and F–Zero, use the UP/DOWN keys to adjust displayed Zero adj: value as close as possible to zero. Then, press Enter.

S–Zero starts. During S–Zero, the Microcontroller takes control as in Auto Mode Zeroing, above. It calculates the differences between successive sam- plings and displays the rate of change as Slope= a value in parts per million per second (ppm/s).

####.## % CO2 Slope=#.### S—Zero

Generally, you have a good zero when Slope is less than 0.05 ppm/s for about 30 seconds.

Once zero settling completes, the information is stored in the analyzer’s memory, and the instrument automatically returns to the Analyze mode.

4.4.1.3 Cell Failure

Cell failure in the 7300A is usually associated with inability to zero the instrument with a reasonable voltage differential across the Wheatstone bridge. If this should ever happen, the 7300A system alarm trips, and the VFD displays a failuremessage.

Cell cannot be balanced

Check your zero gas

Before replacing the sensor:

a. Check your zero gas to make sure it is within specifications.

4-18 Teledyne Analytical Instruments