Function, simulation and test with
COS 3, COS 3-S, COS 3HD
If a sensor with analogue on-site electronics is
connected (COS 3, COS 3-S, COS 3HD, COS
1, TriOxmatic
®
), this is recognised by the
COM 2x3 and the operating mode is auto-
matically switched to »analogue input«.
These sensors also require a ± 8.5 VDC
voltage supply from the COM 2x3. Because of
the analogue on-site signal processing, a
limited
simulation of sensor signals is
possible.
Test possibilities in analogue mode:
• Measure supply voltages (see above)
• Connect intact COS 3 or compatible sensor
• Measure sensor current consumption
(max. 0.5 mA at COS 3)
• Check O
2
measured variable or
temperature value on Liquisys M
or
• connect temperature equivalent resistor of
30 kOhm at terminals 96 and 97
(Display 25 °C)
The table in Chapter 8.8.1 can be used for
additional tests.
• The O
2
input can be tested by measuring
the output DC voltage.
The reference is terminal »0«, the O
2
input
is terminal 18:
. 0 mV
. = 0.0 mgO
2
/l
. –150 mV = O
2
saturation
(at 25 °C = 8.1 mgO
2
/l. Value indicated
dependent on last calibration)
• In measurement mode, the sensor voltage
can be displayed in mV by pressing the
»-« key.
• Due to missing data transfer, Fields E 151
to 159 are empty in analogue mode.
The air pressure measurement in the COM
2x3-WX/-WS can be checked in Field S11.
Caution!
The absolute pressure is displayed
(a normal barometer indicates the relative
pressure referred to sea level and cannot be
used as a comparison).
8.7.2
Oxygen sensors COS 31 / COS 71
Please refer to the operating instructions for
the COS 31/ COS 71 with regard to sensor
maintenance and troubleshooting!
The operating instructions contain detailed
information including:
• Sensor design and function
• Mounting and installation
• Electrical connection
• Start-up and calibration
• Calculation examples and tables for
verification of measured values
• Maintenance, regeneration, cleaning
• Troubleshooting table
• Accessories and spare parts
• Technical data and ordering information
8.7.3
Assembly
Refer to the assembly operating instructions
for maintenance and troubleshooting. The
following assemblies can be used for
COS 31/ COS 71:
• Suspension assembly holder CYH101-A
with immersion pendulum assembly
CYA 611
• Suspension assy. holder CYH101-D with
stainless steel immersion tube
CYH 101-D / -E
• Basin wall mount CYY 106-A with stainless
steel immersion tube CYY 105-A / -B
• Flow assembly COA 250
• Float assembly COA 110-50
8.7.4
Connecting lines and junction boxes
COS 31 / 71 sensors work with a digital inter-
face and therefore are sensitive to electrical
faults and shunting by humidity. Nevertheless,
keep to the recommendations in Chapter
8.8.4. For safe data transfer, always use an
extension cable with twisted wire pairs, e.g.
OMK.
COS 3 sensors and compatibles work with
analogue signal processing and therefore are
also sensitive to electrical faults and shunting
by humidity. For extension purposes, you
require a 7-wire screened cable.
Recommendation: Use original OMK cable.
OM253D08.CHP
Liquisys M COM 223 / 253
Diagnostics and corrective maintenance
Hauser
71
