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Downlook Ultrasonic Sensor
Section 4
4. Select the pH for the first buffer solution (4, 7, or 10 pH) using the
CHANGE CHOICE soft key, then press the ACCEPT soft key to continue.
5. Remove the probe from the first buffer solution, rinse it under distilled
water and place it into the second buffer solution (4, 7, or 10 pH, different
from the first buffer used). Press any key to continue.
6. Select the pH for the second buffer solution using the
CHANGE CHOICE
soft key, then press the
ACCEPT soft key to continue. If the pH probe
is damaged and cannot be calibrated or if the buffer solutions do not fall
within an acceptable range, an error message will be displayed as
shown below.
Another attempt at reading the second buffer solution will be made after
pressing a key. If this fails, it is likely that you have a bad pH probe or bad
buffer solutions. Try a new set of buffer solutions and if that fails try a
different pH probe.
4.10 Downlook Ultrasonic Sensor
Downlook ultrasonic level sensors are available with different beam angles
and deadbands. The 980 Flow Meter uses a 75 kHz Downlook Ultrasonic
Sensor. See Figure 31.
The ultrasonic transducer is mounted over the flow stream at the proper
location for head measurement. To determine the proper location for head
measurement refer to Working with Primary Devices on page 109. The
transducer emits a pulse of sound at a high frequency and awaits for the echo
to return from the surface of the water. The time it takes for this echo to return
is directly related to the distance between the transducer and the surface
water. As the level in the flow stream increases, the time it takes for the echo
to return to the transducer decreases (distance is shorter).
By continuously transmitting these pulses and timing the returning echoes,
the sensor measures the level of the liquid on the flow stream. After
measuring the level, the microprocessor converts the level reading to a flow
rate based on the user-defined characteristics of the primary device.
11:00 AM 21 - APR - 01 ERROR MESSAGE
pH CALIBRATION FAILED-GAIN
AND/OR OFFSET OUT OF RANGE
TRY AGAIN
(PRESS ANY KEY TO CONTINUE)