LaMotte LTC3000wi Turbidity & Chlorine Lab Meter - Manual (Page 81)

The display may show the following messages:
Battery Status
More choices are available and can be viewed by
scrolling up and/or down through the display.
Header Identifi es the current menu and information on units
and reagent systems if applicable.
Footer In the data logging mode the number of the data point
is displayed and the total number of data points in the
memory will be shown. The footer also shows current
time and battery status
 NEGATIVE RESULTS
There are always small variations in readings with analytical instruments.
Often these variations can be observed by taking multiple readings of
the same sample. These variations will fall above and below an average
reading. Repeated readings on a 0.00 sample might give readings
above and below 0.00. Therefore, negative readings are possible and
expected on samples with concentrations at or near zero. This does
not mean there is a negative concentration in the sample. It means
the sample reading was less than the blank reading. Small negative
readings can indicate that the sample was at or near the detection limit.
This is a normal variation that results in a negative reading. A large
negative reading, however, is not normal and indicates a problem.
Some instruments are designed to display negative readings as zero.
In this type of instrument, if the meter displayed zero when the result
was actually a large negative number there would be no indication that
a problem existed. For this reason, the LTC3000we/wi displays negative
numbers for turbidity.
 TUBES AND CHAMBERS
The LTC3000we/wi uses one type of tube (Code 0290) for all test factors.
There is no need for a special turbidity tube.
The handling of the tubes is of utmost importance. Tubes must be clean
and free from lint, fi ngerprints, dried spills and signifi cant scratches,
especially the central zone between the bottom and the sample line.
Scratches, fi ngerprints and water droplets on the tube can cause stray
light interference leading to inaccurate results when measuring turbidity.
Scratches and abrasions will affect the accuracy of the readings. Tubes
that have been scratched in the light zone through excessive use should
be discarded and replaced with new ones.
Tubes should always be washed on the inside and outside with mild
detergent prior to use to remove dirt or fi ngerprints. The tubes should be
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