YSI 6 series Bedienungsanleitung PDF herunterladen (Seite 5)

pHCALIBRATIONTIPS

1. Go to the sonde’s Report Menu and enable the pH mv output. This will allow the sonde to display

the millivolt output from the probe as well as the pH units during the calibration process.

2. Recondition the probe if a slow response in the field has been reported or if it takes more than 90

seconds to stabilize in pH buffer. The procedure to do this can be found in your manual under the

Sonde Care and Maintenance section.

3. In most cases, a two-point calibration is all that is required. Bracket the expected in-situ pH values;

use the three-point calibration only if the in-situ pH value is unknown. Start all calibrations in buffer

4. Calibrate the pH. Rinse the sensor and cal cup with a small amount of pH buffer. Fill the cup so that

the pH probe tip and the sonde’s temperature probe are submerged in buffer. Enter the pH value

based on the solution temperature. Record the pH millivolts for each calibration point. The

acceptable millivolt output for each buffer is shown below.

Buffer 4 = +180 ± 50 mv

Buffer 7 = 0 ± 50 mv

Buffer 10 = -180 ± 50 mv

5. After recording the pH millivolts for the calibration points, you must determine the slope of the

sensor. This is done by determining the difference between the two calibration points that were used.

For example, if we recorded a +3 mv for buffer 7 and a -177 for the buffer 10, then the slope would

be 180. The acceptable range for the slope is 165 to 180. Once the slope drops below 160, the

sensor should be taken out of service.

Warning: Do not use a probe that has given any “Calibration Error” or “Out of Range” warnings.

6. Note: When calibrating any of the flat glass pH sensors you may experience jumpy pH readings in

conditions where static electricity is present. Calibrating in glassware is recommended in these

situations. Also, try to keep your body at least 1 meter from the sonde to prevent the sensor from

detecting your body’s capacitance.

NOTICE: The Calibration Work Sheet and information above is working with a pH probe that is still in

“quality” working order. The pH mv would have to exceed around 70 mv before it would get an out of

“OUT OF RANGE” error message. Therefore, the ± 50 mv is the range at which you should start giving

close attention as to how the probe should be used. Spot sampling would not be as critical as the mv can

be reviewed daily, but a long term deployment should be questioned if to use a probe with an offset at or

greater than 50 mv.

The same would apply to the 165 - 180 slope, we know that a probe can get down to a slope of nearly

155 mv before an error message would occur. But a probe with a slope of 162 should not be used for

any long term deployments.

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YSI 6 series Bedienungsanleitung Seite 5