Thermo Scientific AquaSensors™ DataStick™ Measurement System User Guide
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5.2.1
pH Sensor Head inspection
If the glass electrode is broken replace the sensor head.
If the salt bridge junctions have dried out soak the sensor head in salt bridge storage solution for several hours, or replace it and fill
the reference chamber with new reference solution.
Note:
Any new sensor that has been in storage for more than a few days should be soaked in tap water
or a solution of known pH for at least 30 minutes before reviewing the span and offset performance.
Note:
The electrodes of any pH sensor in storage must be kept moist at all times. Protective caps should
be filled with Thermo Scientific AquaSensors storage solution for best performance. The protective cap
should be placed securely over the sensor head.
If the sensor passes the visual inspection, there are three basic measurement tests that can verify normal operation. The temperature
measurement can be verified with an independent thermometer. Temperature comparisons should be done in liquid as it takes the sensor
much longer to reach steady state in air. The pH offset can be verified in 7 pH buffer. If the reading is more that 0.5 pH units off in 7 pH
buffer, then the sensor needs to be refurbished. The sensor should be stirred if the test is done in a beaker or at least the sensor head
should be swirled around for 10 seconds to make sure the solution gets through the reference junction. The pH span can be verified in a
sample solution that is more that 3 pH units away from 7 pH. Generally 4 pH buffer and 10 pH buffer work well. If the reading is more than
1 pH unit off then the sensor needs to be refurbished or replaced.
Make sure the correct configuration settings have been made:
•
Correct Buffer Standards selected for buffer calibrations
•
Temperature should read within 2 degrees centigrade of the expected value
5.2.2
ORP Sensor Head inspection
If the glass around the platinum electrode is broken replace the sensor head.
If the salt bridge junctions have dried out soak the sensor head in salt bridge storage solution for several hours, or replace it and fill
the reference chamber with new reference solution.
Note:
Any new sensor that has been in storage for more than a few days should be soaked in tap water or
Thermo Scientific AquaSensors ORP Storage Solution for at least 30 minutes before reviewing the offset
performance.
Note:
The salt bridge of any ORP sensor in storage must be kept moist at all times. Protective caps should
be filled with Thermo Scientific AquaSensors Storage Solution for best performance. The protective cap
should be placed securely over the sensor head.
If the sensor passes the general inspection, there are two basic tests that can verify normal operation. If the sensor passes the visual
inspection, there are two basic measurement tests that can verify normal operation. The temperature measurement can be verified with
an independent thermometer. Temperature comparisons should be done in liquid as it takes the sensor much longer to reach steady state
in air. The ORP measurement should be tested with a solution that is at least +200 mV. If the reading is more than 100 mV off then the
sensor needs to be refurbished or replaced.
