Hach D3433B8.99, Руководство пользователя

Страница: 10 / 446

Table 2 Sensors connected to sc digital gateway (continued)
Option Description
Alternating current
frequency Selects the power line frequency to get the best noise rejection. Options: 50 or 60 Hz
(default).
Reset setup Sets the Settings menu to the factory default settings and resets the counters. All sensor
information is lost.
4.3 Adjust the T-factor for non-standard cable lengths
When the sensor cable is extended or shortened from the standard 6 m (20 ft), the resistance of the
cable changes. This change reduces the accuracy of temperature measurements. To correct for this
difference, calculate a new T-factor.
1. Measure the temperature of a solution with the sensor and with an independent, reliable
instrument such as a thermometer.
2. Record the difference between the temperature measured from the sensor and from the
independent source (actual).
For example, if the actual temperature is 50 °C and the sensor reading is 53 °C, the difference is
3 °C.
3. Multiply this difference by 3.85 to get the adjustment value.
Example: 3 x 3.85 = 11.55.
4. Calculate a new T-factor:
• Sensor temperature > actual—add the adjustment value to the T-factor that is on the label on
the sensor cable
• Sensor temperature < actual—subtract the adjustment value from the T-factor that is on the
label on the sensor cable
5. Select Settings > Temperature element (or Temperature sensor) > Temperature factor (or
Factor selection ) and enter the new T-factor.
4.4 Calibrate the sensor
W A R N I N G
Fluid pressure hazard. Removal of a sensor from a pressurized vessel can be dangerous. Reduce
the process pressure to below 7.25 psi (50 kPa) before removal. If this is not possible, use extreme
caution. Refer to the documentation supplied with the mounting hardware for more information.
W A R N I N G
Chemical exposure hazard. Obey laboratory safety procedures and wear all of the personal protective
equipment appropriate to the chemicals that are handled. Refer to the current safety data sheets
(MSDS/SDS) for safety protocols.
C A U T I O N
Chemical exposure hazard. Dispose of chemicals and wastes in accordance with local, regional and
national regulations.
4.4.1 About sensor calibration
Two methods can be used to calibrate the conductivity sensor:
• Dry cal —enter the unique cell constant K and T-factor from the sensor label in the Settings > Cell
constant parameters menu to define the calibration curve.
• Wet cal —use air (Zero Cal) and a reference solution or process sample of known value to define a
calibration curve. A reference solution calibration is recommended for best accuracy. When the
10 English