KROHNE SMARTSENS PH 1590 EN - Manual (Page 22)

4
OPERATION
22
SMARTSENS PH 1590
www.krohne.com 11/2013 - 4002545902 - MA SMARTSENS PH 1590 R02 en
• Press Ok Ok Ok Ok to proceed.
• The message No saving possible No saving possible No saving possible No saving possible appears.
• Press Ok Ok Ok Ok to proceed.
• Select no no no no to deactivate the function manual hold manual hold manual hold manual hold.
• Press Next Next Next Next to leave the calibration menu.
In a fully functional sensor, the optimal slope is -59 mV for each pH unit and the optimal zero
point is 0 mV at pH 7. The slope should at least have a value between -50...-65 mV per pH unit.
Re-calibrate the sensor if the slope does not approximate those limits. The pH sensor ages, the
slope gets flatter and the zero error increases.
4.2 Troubleshooting
CAUTION!
•
Never touch or scratch the pH sensitive glass tip of the sensor.
• Make sure that the sensor tip is clean and dust-free. If necessary, clean the tip as described
on page 24.
CAUTION!
Moisture inside the sensor connector must be avoided! Moisture may cause a shortcut and
deliver erratic readings!
If moisture has entered the connector dry it with air (e.g. hair blower).
Problem Possible cause Remedy
The pH sensor
does not deliver a
signal.
Mechanical damage of the
glass, e.g. small cracks.
This will shortcut the ion
exchange and deliver a pH
7 reading.
Exchange sensor.
Open circuit Check the cable wiring of the sensor cable on the junction box.
Otherwise connect the sensor to the primary master e.g.
PACTware
TM FTD/DTM or to the HART ® handheld to exclude a sensor
damage.
The pH sensor
delivers an
unstable signal.
The diaphragm in the
reference half cell does
not provide good contact
to the process medium
due to drying up or
coatings.
• Clean the diaphragm with hot soap or acid using a soft tissue
(details on page 24).
• Submerge sensor in water and increase the temperature to
+50...+60°C / +122...+140°F.
• Submerge sensor in 3 molar KCl solution at ambient temperature.
The decrease in temperature will cause the reference half cell to
suck in KCl solution through the diaphragm and regenerate the
diaphragms functionality.
High pH value Air bubble in the sensor
tip (no inner buffer
solution)
Protect the sensor tip with a protection cap as descriped on page 12.
Hold the sensor into a vertical position and help by rapid movements
of the wrist to shake the liquid down. Remove the protection cap and
check if there is still an air bubble inside the sensor tip. If necessary,
repeat this procedure one more time.
.book Page 22 Wednesday, October 30, 2013 11:35 AM