Temperature Calibration Procedure - Hach pHD Sensor User Manual

Select pH parameters
1. Select the type of chlorine sensor used - Total CL2 or Free CL2.
2. Select Yes.
3. Select DIFF PH.
4. Select pH.
5. Customize the options:
Option
DISPLAY
FORMAT
FILTER
LOG SETUP
Calibrate the sensor
About sensor calibration
The sensor characteristics slowly shift over time and cause the sensor to lose accuracy. The sensor
must be calibrated regularly to maintain accuracy. The calibration frequency varies with the
application and is best determined by experience.
Recalibrate the sensor whenever disconnected from power and removed from water.

Temperature calibration procedure

One measurement is required for temperature calibration of this sensor. The measurement is made
with the pH sensor in a beaker that contains a sample or reference solution or with the pH sensor
installed in the flow cell.
1. To calibrate the temperature with the pH sensor in a beaker:
a. Put the sensor in the sample or reference solution.
b. Make sure that the sensor is at least half immersed in the liquid
c. Stir the sensor to remove bubbles.
d. Wait for the sensor and solution temperature to equalize. This can take 30 minutes or more.
2. To calibrate the temperature with the pH sensor in the flow cell, install the pH sensor in the flow
cell and turn on the flow. Wait at least 30 minutes after flow is started for the temperature
readings of the pH sensor to stabilize.
3. Push the MENU key and select Sensor Setup, Calibrate, Temperature, Temp Cal.
4. If the passcode is enabled in the security menu for the controller, enter the passcode.
The controller shows "Stabilizing" until the temperature measurement stabilizes and then shows a
temperature measurement.
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.
6. Measure the temperature of the sample or reference solution with a secondary verification
instrument (such as an NIST traceable thermometer).
7. Use the arrow keys to enter the measured value and push ENTER.
Description
Sets the number of decimal places that are shown on the measure screen-XX.XX or
XX.X
Sets a time constant to increase signal stability. The time constant calculates the
average value during a specified time-0 (no effect, default) to 60 seconds (average of
signal value for 60 seconds). The filter increases the time for the sensor signal to
respond to actual changes in the process.
Sets the time interval for data logging-10, 30 seconds, 1,5, 15 (default), 60 minutes.
(Figure 2 on page 12).
English 11