Temperature Calibration - Hach POLYMETRON 9240 Basic User Manual

7. If the mode is set to frequency, then the week and hour data fields will be replaced by a TIME
PERIOD field. Enter the calibration frequency in hours into this field.
8. Finally, in the CALIB ON field, select the channel to be used for calibration. The number of
channels available will depend on the number of channels configured for the instrument. The
sample concentration being measured on this channel must be less than 1 per thousand of the
calibration solution concentration, otherwise an error is signalled during calibration.
Calibration results
After the slope and offset have been calculated, the default parameters, last calibration details and
current calibration details are displayed, along with a "Calibration ok" or "Calibration error"
message. The criteria for accepting or rejecting the calibration is as follows:
• The slope must be within ± 10% of the standard slope
• The offset must be within ± 59 mV from the reference point
If the calibration is accepted, the parameters are updated and the instrument returns to the normal
measurement mode after a short delay.
If the calibration is rejected an alarm is set and the parameters remain unchanged. After a short
delay the analyzer returns to the normal measurement mode.
For details of the calibration results, select the calibration loggings option as described below.
Calibration loggings
1. Select the CALIBRATION LOGGINGS option to view historical information about previous
calibrations.
2. Use the Arrow key to scroll through the data.
Custom adjustment
1. Where the analyzer displays values that are slightly above or below the expected value, the
CUSTOM.ADJ option can be used to manually adjust the measurement value.
2. Enter a positive or negative value which will be added to the measurement value. This option can
only be used to make minor adjustments. The allowable adjustment value is between -0.1 ppb
and +0.1 ppb.
3. If the displayed and expected values differ significantly, the analyzer should be recalibrated.

Temperature calibration

1. Select the TEMPERATURE CALIB. option to calibrate the temperature electrode.
2. The measured temperature reading is displayed in the raw temp field.
3. Take a temperature reading with a certified thermometer and press OK to continue.
4. Then enter this temperature reading into the CAL.TEMP. field.
5. Press OK to calibrate.
VERIFICATION
This option allows you to verify the measurement using a solution of known sodium concentration.
Concentration of the known solution should be higher than 20 ppb (100 ppb is recommended) to
ensure a preparation step in a range with lower risks of contamination.
1. First enter the concentration of the verification solution in the VALID. SOL field.
2. Select START to commence the process.
3. The first step of this cycle allows the reactivation of the electrode. The message SENSOR
ACTIVATION is displayed. Select Yes to reactivate the sensor. Select No if time is more
important than accuracy.
22 English