Suntex PC-3310, Operation Manuals, Page: 46 / 56

7.3 pH Calibration
The instrument provides multi-point standard buffer solution calibration. You may decide how
many points to calibrate the measurement system(up to 3-point). The principle is according to
“Method of Least Squares”. Apply linear regression to calibration the electrode’s slope and zero
point (Any, Offset or Zero point).
When calibrating a electrode, you may calibrate 1 to 3 point by any sequence to provide linear
regression for mV and pH multi-calibration of a electrode, and to show the electrode’s slope and
zero point(Any, offset or Zero point) at 25
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C. The electrode’s slope rate which is actual slope
divided by theoretical slope and the sensitivity shows in percentage in the display. In addition, the
display shows the linear regression determination coefficient, R2, of the electrode and buffer
solution to provide you an estimation of an electrode’s regression suitability. According to different
combination of standard buffers, the TECH, NIST, Any buffer solution calibration modes are
provided.
7.3.1 TECH Buffers mode
The electrode is automatically calibrated according to pH value and temperature of TECH
standard buffers (pH4.01, pH7.00, pH10.00). The range of zero point and slope of the electrode
is also determined. If one of them is over the range, the display shows error message of zero
point and slope failure. (See appendix Table 1, pH/temperature table of TECH standard buffers)
7.3.2 NIST Buffers mode
The electrode is automatically calibrated according to pH value and temperature of NIST
standard buffers (pH1.68, pH4.01, pH6.86, pH9.18, pH 12.45). The range of zero point and slope
of the electrode is also determined. If one of them is over the range, the display shows error
message of zero point and slope failure. (See appendix Table 2, pH/temperature table of NIST
standard buffers)
7.3.3 Any Buffers mode
The electrode measures mV value of different standard solutions. According to theoretic
slope and the temperature of standard solutions, the display shows a approximate pH value. Then,
you can calibrate the electrode by freely adjust the pH value as those of the standard solutions’.
There is not a zero point range failure determination by the instrument but only the slope range
determination. If the slope is over the range, the display shows error message of slope failure.
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