Hach Lange 2100AN, Instrument Manual

Page: 34 / 108

34
SECTION 3,
continued
3.1.3 Using the
SIGNAL AVG
Key
Turning on Signal Averaging causes a number of measurements to accumulate in
a measurement data storage buffer. The number of measurements stored and used
for displaying the average reading can be specified by the analyst (between 1 and
15 readings). Three measurements are averaged with Signal Averaging off. The
initial value is updated immediately with Signal Averaging on. Subsequent values
are an average of readings accumulated in the buffer. As the buffer accumulates
the number of readings specified, the display shows the cumulative average.
Press
SETUP
to change the number of readings used for the Signal Averaging
mode (set at 10 initially). One of the green LED digits in the mode display begins
to flash. Press the up, down and right arrow keys to select the setup number
09
.
Press
ENTER
. Next, enter the number of signal averages using the edit keys.
Press
ENTER
to accept the number of readings displayed. Press
SETUP
to exit the
setup mode. Pressing
UNITS/Exit
at any time, prior to accepting the new value,
exits the setup mode leaving original values intact. The largest acceptable Signal
Averaging number is 15; the instrument uses 15 measurements if a larger number
is specified.
Pressing
ENTER
when Signal Averaging is selected on clears the data buffer
and provides an immediate update. If power is turned off and then restored,
the instrument re-initializes to the Signal Averaging condition selected during the
last measurement.
3.1.4 Using the
FLOW
Key
Press the
FLOW
key to enter or exit the automated
FLOW
mode that is used in
conjunction with the automated Flow-Cell system. Refer to Section 5.2.2 on
page 54 for more information.
3.1.5 Using the
LINE FEED
Key
Press the
LINE FEED
key to advance the internal printer paper one line each time
the key is pressed.
3.1.6 Using the
RATIO
key
Turn Ratio on and off by pressing the
RATIO
key. A lighted annunciator indicates
the Ratio function is selected on. A flashing annunciator light and 9s on the large
LED display indicate that the measurement is greater than 40 NTUs and the Ratio
mode is selected off. Press the
RATIO
key to clear the over-range condition; the
Ratio annunciator is lighted.
With Ratio on, the 90°, transmitted and forward scatter detectors are used to make
the measurement. When NTU values greater than 4000 are measured, the back
scatter detector signal is incorporated into the measurement.
Measurements with Ratio on and measurements with Ratio off are nearly
equivalent for turbidity measurements less than 40 NTU if interferences due to
color or light absorbing particles are not present. However, Ratio on compensates
for instrumental and sample variables. Operation with Ratio on is recommended
for most measurements. Refer to Section 1.3 on page 11 for a more detailed
discussion of Ratio on vs. Ratio off measurements.