12
SS SENSOR CALIBRATION
To do a complete calibration, three steps are required. The analyzer must first be zeroed, and then a
sample/snapshot is taken. After the sample has been analyzed, the span of the analyzer can be adjusted
to the sample. As long as the lenses are kept clean, frequent recalibration should not be necessary.
Every six months should be more than adequate for a complete calibration.
Any optically based device for measuring suspended solids should only be span calibrated against a
typical sample of the actual process water being measured. Synthetic laboratory standards will add
unnecessary inaccuracies to the system and are not recommended. The Model 2000 utilizes its
microprocessor memory in a unique way to make span calibration as easy and accurate as possible. This
calibration is performed as a two step process. First, the SNAPSHOT SAMPLE function of the analyzer is
used to store actual process conditions to the instrument’s memory. Later, when standard laboratory
analysis results are available for those previous conditions, the analyzer’s SPAN function will recall the
stored value and allow the user to adjust the span value accordingly.
The range of operation of the Model 15 sensors is 0-30,000 mg/l total suspended solids. Within this
range, accuracy and repeatability are only specified over a range of +/- 50% of the user’s point of
calibration. Accuracy will be +/- 5% of the current reading or +/- 100 mg/l, whichever is greater.
Repeatability will be +/- 1% of the current reading or +/- 20 mg/l, whichever is greater.
The range of operation of the Model 15L sensor is 0-1500 mg/l total suspended solids. Within this
range, accuracy and repeatability are only specified over a range of +/- 50% of the user’s point of
calibration. Accuracy will be +/- 5% of the current reading or +/- 2 mg/l, whichever is greater. Repeatability
will be +/- 1% of the current reading or +/- 2 mg/l, whichever is greater.
Sensor Zero
Submerge the sensor in clean water. It is important that the water used to zero the sensor be clean.
At the very least use potable water for this, and distilled water is even better. Do not use plant process
water of any type.
Select the "ZERO" option from the calibrate menu using the up and down arrow buttons. Press the
"ENTER" button. With the sensor submerged in clean water, wait about 15 minutes and then press
"ENTER". The analyzer will take about sixty seconds to zero. The display will return to the calibrate menu
automatically when it is finished. Press the "MENU" button to exit or use the up and down arrow buttons
to select another calibration mode.
Snapshot
With the sensor submerged in the process to be measured and stable, select the "SNAPSHOT"
option from the calibrate menu using the up and down arrow buttons. Press the "ENTER" button.
Pressing the "ENTER" button again will cause the analyzer to take a snapshot of the conditions. The
analyzer will take about sixty seconds to obtain a sample value. The display will return to the calibrate
menu automatically when it is finished. At this point, you have NOT altered the calibration of the analyzer
at all; you have only stored the conditions of the process water in memory for future use. Press the
"MENU" button to exit or use the up and down arrow buttons to select another calibration function.
At this time, take a physical sample of the process water from the same location so that it can be
analyzed using standard laboratory techniques to determine suspended solids concentration. This value
will be used during the span calibration.
Sensor Span
This step is performed when an accurate laboratory value has been obtained from the sample
previously taken during the SNAPSHOT procedure. Select the "SENSOR SPAN" option from the calibrate
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