ChannelMag
Section 4 Maintenance
4.1 Cleaning
4.2 Zero Span Checking
Under typical operating conditions the ChannelMag sensor requires no maintenance. Due to the uniquely high signal to media noise ratio, the affects of such coatings as algae, sewage grease, calcium carbonate, iron oxides or similar coatings have no affect on published accuracy. As such cleaning of coatings is normally unnecessary.
Should there be silt or similar
When the CM2 is in a recess in the bed of the channel, it is recommended to have its upper surface slightly above the bed of the channel, but not more than ½” (12mm). This avoids excessive silt or similar build up, as well as avoiding too much turbulence due to the step from the bed to the upper surface. If more than ½” (12mm) is required, then the step to the upper surface should have suitable grouting at an angle of less than 15 ë.
With the ChannelMag sensor connected to the 4411e transmitter, check for zero and span in accordance with the 4411e Instruction Manual. This confirms the electrical function of the transmitter.
Note: Bad grounding will not affect the electrical zero and span test.
4.3Effect of Moisture Ingression
The exciter coils of the ChannelMag sensor should be checked at the transmitter end. Remove from terminals 4, 5 and shield 6. There should be a minimum 10Meg Ohms (typically > 20Meg Ohms) between 4 and 6 and 5 and 6 respectively. If there is less than 10Meg Ohms, moisture has probably leaked into the sensor and /or the cable, resulting in signal instability. The cable should be inspected for damage or dried out or cut away where any moisture may be. If the sensor has leakage it must be returned to ARKON or approved representative.
4.4Effect of a Grounded Electrode
4.5Effect of One Sensor Of Two Inoperative
To check if there is electrical ground at the electrodes, the cable ends 24 and shield and 25 and shield respectively are removed from the terminals of the transmitter. The resistances should approximately the same between each and between 100k Ohms to 5 M Ohms. If any electrode is grounded the signal will be at approximately ¾ of the normal signal. Remove anything highly conductive between the appropriate electrode and ground.
If there are two ChannelMag sensors used as one flow system in a channel, the electrodes and coils are wired in parallel. Should one sensor coil become defective, then the system will continue to operate, but there will be a small inaccuracy due to operating with only one sensor. If this is unacceptable a replacement sensor can be installed at a convenient time. The erroneous sensor can be determined by checking as above in the junction box.
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