SENTRON A120-001, Technical Manual

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5.2.2 Performing a multi-point calibration
To rule out erroneous multi-point calibrations, the calibration can only take place for an increasing or
decreasing pH sequence.
Multi-point calibration sequence :
For example a calibration in pH 4 – 7 – 10 buffer.

Rinse the probe with deionized water.

Place ISFET sensor and reference in the first calibration buffer solution. In this case pH4
buffer.

Initiate the calibration process by sending the S tart Calibration command: CLR!<CR>

Wait for the AD Converter or USB interface module to acknowledge, receive: 082 013 013
The AD converter or USB interface module is now ready to receive the first calibration command
bytes of the buffer sequence…

Initiate the pH4 calibration by sending the calibration pH 4 command: 112!<CR>
Allow some time for the module to stabilize (this may take up to 2 minutes maximum)…

Wait for the module to stabilize, receive bytes: 002 013 010
Rinse the probe with deionized water.
Place ISFET sensor and reference in the next calibration buffer solution, pH 7.

Initiate the pH7 calibration by sending the calibration pH 7 command bytes: 113!<CR>
Allow some time for the module to stabilize (this may take up to 2 minutes maximum)…

Wait for the module to stabilize, receive bytes: 003 013 010
Rinse the probe with deionized water.
Place ISFET sensor and reference in the next calibration buffer solution, pH 10.

Initiate the pH10 calibration by sending the calibration pH 10 command bytes: 114!<CR>
Allow some time for the module to stabilize (this may take up to 2 minutes maximum)…

Wait for the module to stabilize, receive bytes: 004 013 010
When performing even more calibration points, repeat this part for each extra desired point.

End the calibration process, send: QIT!<CR>

Wait for the module to confirm calibration end, receive: 084 013 010
The calibration is completed.
Send the “end calibration command bytes” just once after the last performed calibration point.