Danfoss AKS 41 Liquid Level Transmitter
Section 9
Publication 9-45
Issue 1 : 10/11
Page 5 of 18
The capacitive rod can measure the level of conducting as well as non-
conducting liquids.
If the rod is partially immersed in a conducting liquid, for example, R717
(ammonia) or R718 (water).
On the part of the rod that is surrounded by liquid, the outer tube is
short-circuited to the teflon insulation. This produces an effect as if
the distance between the outer tube and the centre electrode has
become smaller which will cause an increase in the rod’s
capacitance. This change of capacitance is converted into an
output signal between 4 and 20 mA.
If the rod is partially immersed in a non-conducting liquid, for example,
R134a.
When the liquid rises between the outer tube and the inner
electrode, it displaces the gas otherwise present. As the liquid has
a higher dielectric constant than the gas, a rising liquid level is
registered as an increase in the rod’s capacitance and hence
results in a higher 4 to 20 mA output signal.
4.
Technical Data
P
ARAMETER
D
ETAILS
General
Enclosure
IP 65
Max working press
100 bar g
Temperature range
-60 °C to +100 °C
Refrigerant
R717 (factory setting), R22, R404a, R134a, R744 and R718 (R717 and
R718 give the same output signal)
Materials
Thread: stainless steel AISI 303
Reference tube: stainless steel AISI 304
Inner electrode: steel, PTFE coated
Top housing: cast aluminium
Environment
-25 to +55 °C during operation, -40 to +70 °C during transit.
20 to 80 % Rh (not condensed).
No shock influence or vibrations.
Approvals
EMC directive 89/336/EEC
EMC directive 92/31/EEC
EN 50081-1 and EN 50082-1
Electrical
Power supply
24 V ac -15 %/+25 % 50/60 Hz or 24 V dc ±10 %
Power consumption
1.5 W
Transmitter output
4 to 20 mA
Max load resistance
500
Ω
Connection
4-pole plug DIN 43650
Nomenclature
X X X X X X
Consecutive number
Serial number
Production year
Production month
Product type (code number)
Version number
The nomenclature code can be found inside the transmitter housing.
Table 1 Technical Data