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Measurement techniques
Measurements may be made with different operation mode settings and
optional accessories.
Calibrate the instrument whenever the sample cell pathlength is
changed.
Manual or automatic ranging
The manufacturer recommends that ranging be set to automatic for most
measurements.
The setting can be changed at any time during sample measurement.
Push RANGE repeatedly to step the instrument from automatic ranging
to manual ranging and then scroll through the manual range settings.
"MANUAL" is shown above the Range Mode label on the instrument
when manual ranging is selected. "AUTO" is shown below the Range
Mode label on the instrument when automatic ranging is selected.
Notes:
• When manual ranging is selected, the display flashes all 9s when the
sample being measured is greater than the selected range. The
display flashes all 0s when the sample measured is less than the
selected range.
• When automatic ranging is selected, the display flashes 9s when the
sample is greater than the maximum range of the instrument. The
display flashes 9s when Ratio is off and the measurement is greater
than 40 NTUs (268 nephelos or 9.8 EBCs). Turn Ratio on to increase
the range. Refer to
Measure over-range samples
• When automatic ranging is selected, the display flashes all 0s when
the measurement is less than the range of the instrument or a
negative value. Calibrate the instrument. When measuring color,
absorbance or transmittance, set the zero reference point again.
Signal averaging on or off
Signal averaging corrects for reading fluctuations that are caused by
random drifting particles in the sample. When signal averaging is on, an
average reading is calculated every 3 seconds and shown on the
display.
The manufacturer recommends that signal averaging be on for most
measurements.
Push SIGNAL AVG to turn signal averaging on or off. The SIGNAL AVG
light turns on when signal averaging is on.
Push ENTER when signal averaging is on to erase data in the signal
averaging buffer and provide an immediate update on the display as
necessary. This is especially useful when measuring samples with large
differences in turbidity.
To change the number of measurements that are used to calculate the
average reading (default=10):
1. Push SETUP. The SETUP light turns on.
2. Select 09 using the arrow keys.
3. Push ENTER.
4. Use the arrow keys to select the number of measurements—1 to 15.
Note: If a number greater than 15 is selected, 15 measurements will be used.
5. Push ENTER.
6. Push SETUP.
Ratio on or off
Ratio on provides very good linearity, calibration stability and a wide
measurement range. Ratio on helps correct for interference when color
is present in the sample that absorbs at the wavelength of incident light.
The manufacturer recommends that Ratio on be used for most
measurements. Ratio must be on to measure samples greater than
40 NTUs (268 nephelos or 9.8 EBCs).
on page 25.
Ratio can be turned on for NTU, EBC, NEP and ASC -1- and -2-
measurements.
Push RATIO to turn Ratio on or off. The Ratio light is on when Ratio is
on.
Notes:
• If the sample being measured is greater than 40 NTU (or equivalent)
and Ratio is off, the display will show 9s and the RATIO light will flash.
Push RATIO to turn Ratio on and remove the over-range condition.
• Measurements with Ratio on and measurements with Ratio off are
almost the same for turbidity measurements that are less than 40 NTU
English 33
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