Hach 3700 Série Manuel D'utilisation De Base page 17

Solution Concentration
NaOH 0–16%
CaCl 0–22%
2
6.3 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.
Note: This procedure applies only to sensors with a PT1000 temperature element. Sensors with a
PT100 temperature element are less accurate.
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 an 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 on the sensor cable
• Sensor temperature < actual—subtract the adjustment value from the T-factor on the sensor
cable
5. Enter the new T-factor in the Configure, Temp Element menu.
6.4 Calibrate the sensor
Explosion hazard. Removal of a sensor from a pressurized vessel can be dangerous. Reduce the
process pressure to below 10 psi before removal. If this is not possible, use extreme caution. Refer to
the documentation supplied with the mounting hardware for more information.
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.
Chemical exposure hazard. Dispose of chemicals and wastes in accordance with local, regional and
national regulations.
6.4.1 About sensor calibration
The wet cal method should be used to calibrate the conductivity sensor:
• 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
process sample is used, the reference value must be determined with a secondary verification
Table 4 Built-in concentration tables (continued)
Solution
HNO
H
W A R N I N G
W A R N I N G
C A U T I O N
Concentration
0–28%, 36–96%
3
SO 40–80%, 93–99% or 0–30%
2 4
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