Ionics Instruments 2004 Page 9-5 DLM 30007-08 Rev. A
8. If the instrument has been used for measuring higher levels of TOC
(TOC> 50 ppb), make TOC measurements for at least 6 hours,
preferably overnight. If the instrument has been used for lower level
measurements (TOC < 50 ppb), make TOC measurements for at least
1 hour.
9. Stop the analyzer by pressing ENTER, scrolling to STOP TOC, and
pressing ENTER again.
10. From the MAIN menu, select HISTORY and press ENTER.
11. Calculate and record the average value from the last five TOC
measurements on the calibration worksheet.
12. Determine if the value is within the specified range of –0.1<TOC<+0.1
and record on the worksheet. If the value is within the range, there is
no need to change the TC Zero Offset; proceed to Step Five. If the
value is outside of the range, proceed with the TC Zero Offset
procedure below.
Step 3 – Enter new TC Zero Offset:
1. Press CLEAR to return to the MAIN menu. Scroll to CALIBRATE and press
ENTER.
2. Scroll to TC ZERO OFFSET and press ENTER to display the TC ZERO
CORRECTION screen and the current value of the offset. Record the
current offset value on the calibration worksheet.
3. Calculate the new TC Zero Offset using the formula:
New TC ZERO OFFSET = (Initial TC OFFSET) – (Avg. TOC Value)
Record the value on the calibration worksheet.
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