Danfoss AKS 41 Liquid Level Transmitter
Section 9
Publication 9-45
Issue 1 : 10/11
Page 17 of 18
When the programming push-button is pressed, .the 4 to 20 mA signal
increases in 2 mA steps, where each step is maintained for 4 seconds. If
the programming button is released at a certain step, the actual liquid
level is calibrated to the value the current has reached.
Release the programming button when the current has reached 4, 6, 8 or
10 mA to calibrate for minimum liquid level, wait until the current has
reached 12, 14, 16, 18 or 20 mA to calibrate for maximum liquid level.
Example:
AKS 41-12, insertion length 1200 mm
Lowest attainable liquid level = 100 mm measured from the end of
the rod.
Highest attainable liquid level = 950 mm measured from the end of
the rod.
A change in liquid level over the whole insertion length of 1200 mm will
give a change in the output signal of 20 mA – 4 mA = 16 mA
(disregarding the lowermost 35 mm of the rod and the uppermost 45 mm
which do not count). Therefore, a 1 mA change in signal current
corresponds to a change in liquid level of 1200/16 = 75 mm.
A signal current of 6 mA therefore corresponds to a liquid level of 2 x 75
= 150 mm and a signal current of 12 x 75 = 900 mm. As the liquid level
can be adjusted between 100 and 950 mm, it is possible to calibrate the
liquid level transmitter at the 6 mA minimum point and the 16 mA
maximum point.
(a)
Measure the 4 to 20 mA signal and use the shorting strap as
already described.
(b)
Bring the liquid level to its lowest point, 50 mm above the end of
the rod.
(c)
Press the programming button and keep it pressed. When the
output signal reaches 6 mA, release the button.
(d)
Wait 10 seconds until the signal has adjusted itself to 4 mA, the
minimum calibration point has now been saved to memory.
(e)
Bring the liquid level to its highest point, 900 mm above the end of
the rod.
(f)
Press the programming button and keep it pressed. When the
output signal reaches 16 mA, release the button.
(g)
Wait 10 seconds until the signal has adjusted itself to 4 mA, the
maximum calibration point has now been saved to memory.
(h)
After calibration is complete, remove the meter from the DIN plug
and reassemble. Remove the shorting strap from across the two
pins and store by placing over one of the two pins.
12.5.
Signal Damping (Early Version)
Same as the later version of the AKS 41; refer to 6.4.
