Hach Sigma 950, Инструкция по эксплуатации инструмента, Страница: 37 / 146

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Sensor Installation
3. Select Standard as the type of Ultrasonic Transducer using the
CHANGE CHOICE
soft
key. Press
ACCEPT
to continue.
Temperature Time Constant
The speed of sound in air varies with the temperature of the air. The ultrasonic sensor is
equipped with temperature compensation to help eliminate the effect of temperature
variation under normal site conditions. The transducer must be equal to the ambient air
temperature at the site prior to calibration for optimum results. The manufacturer also
recommends that sensors be shielded from direct sunlight for this reason.
4. Enter the ambient air temperature at the transducer location. For optimum results,
allow enough time (100 minutes) to ensure that the sensor is at equilibrium with the
surrounding ambient temperature. Press
ACCEPT
to continue.
5. Select the Liquid Depth method and enter the new level.
6. Take a physical measurement of the liquid depth and enter the value.
7. Press
ACCEPT
when finished.
6.1.3.2 Sensor Height
This method requires you to enter the distance between the face of the ultrasonic sensor
and the zero flow point in the primary device. The zero flow point in a primary device is
the level at which flow ceases. In a round pipe the zero flow point would typically be the
invert or bottom of the pipe. In a V-notch weir the zero flow point occurs when the liquid
behind the weir is level with the bottom of the ‘V’. (There would still be liquid behind the
weir plate but it would not be contributing to flow). Sensor Height calibration is generally
used when access to the primary device is difficult (such as confined space entry in a
manhole) or there is no liquid flowing during installation of the flow meter.
1. From the Main Menu, select
OPTIONS>ADVANCED
OPTIONS>CALIBRATION>ULTRASONIC SENSOR.
2. Select Calibrate U-Sonic using the
UP
and
DOWN
soft keys. Press
SELECT
.
3. Select Standard as the type of Ultrasonic Transducer using the
CHANGE CHOICE
soft
key. Press
ACCEPT
to continue.
4. Enter the ambient air temperature at the transducer location. For optimum results,
allow enough time (100 minutes) to ensure that the sensor is at equilibrium with the
surrounding ambient temperature. Press
ACCEPT
to continue.
5. Select the Sensor Height method and enter the new level.
6. Enter the distance from the face of the transducer to the zero flow point of the
primary device.
7. Press
ACCEPT
when finished.
6.1.3.3 Setting the Invisible Range
1. From the Main Menu, select
OPTIONS>ADVANCED
OPTIONS>CALIBRATION>ULTRASONIC SENSOR.
2. Select the Invisible Range option using the
UP
and
DOWN
soft keys. Press
SELECT
to
continue.
3. Enter the Distance to End of the Invisible Range using the keypad.
4. Select either inches or centimeters using the
CHANGE UNITS
soft key. The distance
must be greater than the minimum deadband of 25.4 cm (10 in.) for the 75 kHz
sensor and 38.1 cm (15 in.) for the 50 kHz sensor.
5. Press
ACCEPT
when finished.