Calibration
Calibration is carried out in 2 stages; firstly set the zero point, then the 100% value. As the
sensor is going to be lowered to the bottom of the tank it is important that attention is paid to
any hazards such as moving scrapers below the surface of the tank.
Set Zero
Set the rotary switch to ‘motor stop’ and take the sensor down to the bottom of the tank by
taking loops of cable off the drum. Once the cable is close to the bottom of the tank gently raise
and lower the sensor and it will be possible to ‘feel’ the bottom of the tank. Use the ‘motor up’
position of the rotary switch to move the sensor such that it is approximately 25 mm from the
bottom of the tank. Press the Red Zero push button to set the zero point, it is sometimes
necessary to press this button a few times to ensure a correct zero setting.
It is important that the zero point is set above the bottom of the tank, if the sensor is allowed to
drag on the floor of the tank damage can occur and there is a danger that the sensor can become
entangled in the scraper mechanism.
Set Span
Now use the ‘motor up’ position to bring the sensor to the water surface. It is normally
advisable to leave the bottom part of the sensor (approximately 50 mm) under the surface.
Set the rotary switch to ‘motor stop’ and use the Top Limit control to set the 3 digit LED
display to 100.
It is advisable to run the instrument back down to 0 to confirm that the calibration has been
performed satisfactorily.
Controls and Settings
Page 12
