TM8400B-L-00
1 November 2004
(f) Average instrument readings for 15 to 30 seconds to smooth out the variations
caused by small changes in the bath temperature (±0.5 mK is equivalent to ±2
digits).
(g) When leaving the instrument for more than an hour between readings, the cell
should be filled with distilled water and the pumps turned off. If the instrument
sits idle for prolonged periods, leave distilled water in the cell and shut off the
power. When the power is restored, fill the cell with salt water.
(h) The STANDBY number is used to determine electronics drift from
standardization. It cannot be used to determine standardization stability since it is
not affected by bath temperature or bath temperature variations. If in doubt
restandardize.
(i) Typical flushing volumes required to measure a sample of 35 PSU salinity water
STARTING WITH DISTILLED WATER IN THE CELL (the most rigorous
condition) are as follows:
- within 100 ppm after 3 flushes.
- within 10 ppm after 7 flushes.
- within 3 ppm after 8 flushes.
- within 1 ppm after 10 flushes.
- confirmation of reading within 1 ppm after 14 flushes.
These numbers are typical assuming approximately 15 ml per flush and read cycle. If the
salinity change is less than 5 PSU, typically 50 ml or three or four flushes are required to
be within a salinity of 0.003 PSU. Note that the final answer is not determined by an
exact number of flushes but repeatability of the readings. Remember that 1 count of the
last digit on the display (±1 digit) is approximately 0.0002 PSU at 35 PSU.
6.6. SAMPLE HANDLING FOR OPTIMAL ACCURACY
The following methods are suggested to obtain the best possible measuring results.
6.6.1. METHOD TO REMOVE SAMPLE BOTTLE AND LEAVE CELL FULL
(a) When cell is full, switch pumps off.
(b) Turn FLOW RATE knob completely counter-clockwise.
(c) Remove sample bottle. Water will remain in the cell and in the sample fill tube.
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