PART THREE - OPERATION
SECTION 4 - CALIBRATE MENU
Rev. 7-1201
Model P63 pH Analyzer
43
Arbitrary Buffer Method
☞
Reasons to Use:
1. When you don’t consistently use the same buffer(s).
2. When you don’t want to configure the analyzer for cali-
bration with pre-defined buffers.
3. When you don’t have pH buffers with values contained
in one of the analyzer’s five buffer sets.
4. When you infrequently calibrate (not recommended).
Advantages/Disadvantages:
This method is easy to perform but if you don’t enter the
exact buffer value shown on the buffer bottle chart corre-
sponding to the buffer’s actual temperature, measured pH
readings will be slightly less accurate.
General Procedure:
You can perform a single or two-point calibration using the
“Arbitrary Buffer” method. However, two-point calibration is
strongly recommended. Any buffer(s) or solution(s) of
known pH value can be used for calibration. Since pH buff-
ers are most commonly used, they are referenced in the
following procedure. Typically, pH 7 and pH 4 buffers are
used. (pH 10 buffer is also readily available but is not as
stable, particularly at extreme temperatures.)
NOTE:
For best accuracy, use buffers with values ap-
proximately equal to the normal pH value of the
process. Example: If the process is normally 3.5
pH, it is best to use pH 4 and pH 7 buffers rather
than pH 7 and pH 10 buffers. Ideally, one of the
calibration points should be 3.5 pH.
1.
Immerse the sensor in the buffer.
Important: Allow the
sensor and buffer temperatures to equalize.
De-
pending on their temperature differences, this may take
30 minutes or more.
2.
Determine the temperature of the buffer by using the
analyzer’s temperature measuring capability. (The pH
value of a buffer changes slightly as its temperature
changes.)
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