Hach 3700 Series Basic User Manual page 20

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.
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.
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
instrument. Be sure to enter the T-factor in the Configure menu for accurate temperature
compensation.
During calibration, data is not sent to the datalog. Thus, the datalog can have areas where the data is
intermittent.
Zero calibration procedure
Use the zero calibration procedure to define the unique zero point of the conductivity sensor. The
zero point must be defined before the sensor is calibrated for the first time with a reference solution
or process sample.
1. Remove the sensor from the process. Wipe the sensor with a clean towel or use compressed air
to make sure the sensor is clean and dry.
2. Push the MENU key and select Sensor Setup, [Select Sensor], Calibrate.
3. Push ENTER to select Zero Cal.
4. If the passcode is enabled in the security menu for the controller, enter the passcode.
5. Select the option for the output signal during calibration:
Option Description
Active The instrument sends the current measured output value during the calibration procedure.
Hold The sensor output value is held at the current measured value during the calibration procedure.
Transfer A preset output value is sent during calibration. Refer to the controller user manual to change the
preset value.
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