COMAC CAL FLOW 38 Use and care manual

Manual FLOW 38 Page 1 (total 54) COMAC CAL s.r.o.
FLOW 38
Ver.8.2x
Installation and technical conditions
Date of issue 31/10/2019

Manual FLOW 38 Page 2 (total 54) COMAC CAL s.r.o.
Contents:
Description of device................................................................................................................................4
Scope of delivery ..................................................................................................................................4
Storage conditions....................................................................................................................................5
Warranty...................................................................................................................................................5
Installation in pipeline.............................................................................................................................6
Important information for selection of location....................................................................................6
Sources of disturbances.........................................................................................................................6
Installation examples.............................................................................................................................7
Actual installation in pipeline...............................................................................................................9
Installation check ................................................................................................................................16
Wiring.....................................................................................................................................................17
Important information.........................................................................................................................17
Installation of the meter's detached evaluation unit............................................................................18
Meter wiring........................................................................................................................................19
OUT1 / OUT2....................................................................................................................................20
Current output .....................................................................................................................................21
The external button to reset the user volume Vnull............................................................................22
Data output..........................................................................................................................................22
Protection degree.................................................................................................................................22
Replacement of tube fuse in the meter................................................................................................23
Wiring check.......................................................................................................................................23
Putting into operation............................................................................................................................24
FLOW 38 OPERATING INSTRUCTIONS..........................................................................................25
Basic button functions.........................................................................................................................25
Special button functions......................................................................................................................25
Password setting..................................................................................................................................25
Basic menu..........................................................................................................................................26
Flow meter settings.............................................................................................................................27
Expansion module..................................................................................................................................38
Turning the FLOW 38 display...............................................................................................................41
User adaptation ...............................................................................................................................41
Technical data........................................................................................................................................43
Factory settings ......................................................................................................................................45
Table with flow ranges for individual DN sizes....................................................................................46
Basic sensor sizes ...................................................................................................................................47
Nomogram for quick proposal of the measured place..........................................................................51
Reduction in DN pipe.............................................................................................................................51
Faults and their symptoms during measurement .................................................................................52

Manual FLOW 38 Page 3 (total 54) COMAC CAL s.r.o.
Flow sensor cleaning .............................................................................................................................52
Servicing.................................................................................................................................................52
Order code ..............................................................................................................................................53
Returning the meter to COMAC CAL s.r.o...........................................................................................54

Manual FLOW 38 Page 4 (total 54) COMAC CAL s.r.o.
Description of device
The FLOW 38 meter is based on measurement principle by a well-known Faraday's electromagnetic
induction law according to which an electric voltage is induced during the flow of a conductive liquid
through the flow meter magnetic field. This is picked up by two electrodes in direct contact with the
measured medium and evaluated in the electronic unit.
The FLOW 38 type of induction meters are suitable exclusively for measurement of volumetric flow of
electrically conductive liquid substances with a minimum conductivity of 20 S/cm (at a lower
conductivity, upon agreement with the manufacturer).
Meters are designed for flow measurement where the velocity of liquid is in the range of 0.01...12 m/s.
The best measurement accuracy can be obtained in the range of 1...10 m/s.
Scope of delivery
Accessories vary according to the variant of flow sensor and above standard optional features.
Threaded design
Electronic evaluation unit with a fixing bracket for wall mounting (not for the compact design), flow
sensor (in case of compact design, the electronic unit is integral part of the flow sensor), connecting
grounding cable, installation manual.
Sandwich design
Electronic evaluation unit with fixing adapter for wall mounting (not for the compact design), flow
sensor (in case of compact design, the electronic unit is integral part of flow sensor).
Flanged design
Electronic evaluation unit with fixing adapter for wall mounting (not for the compact design), flow
sensor (in case of compact design, the electronic unit is integral part of flow sensor), connecting
grounding cable, installation manual.
Food industry design
Electronic evaluation unit with a fixing bracket for wall mounting (not for the compact design), flow
sensor (in case of compact design, the electronic unit is integral part of the flow sensor), adapter piping
connection according to DIN 11851, installation manual.
In case of detached design, a special cable for connection of the meter (it must not be extended or cut
short) is part of the flow sensor.

Manual FLOW 38 Page 5 (total 54) COMAC CAL s.r.o.
Storage conditions
The temperature during transportation and storage of the meter must be within the range of -10 °C to
50 °C.
Wooden boards installed on the flanges in the factory are used for protection of lining on the flanges
during storage and transportation (for PTFE lining). Remove these protective boards just before
installing in the pipeline!!!
Do not lift the flanged meters by the transducer head or by the connecting box of the detached design
during transportation! Use slings and place them round both process connections for transportation of
meters up to DN150 (chains may damage the meter head)! Use only the holes between the flanges and
sensor for transportation, lifting and installation of the sensor in piping in case of DN200 and bigger!!!
Warranty
Unprofessional installation or using the induction meters (devices) may result in a loss of warranty as
well as failure to comply with installation or operating conditions according to this manual.

Manual FLOW 38 Page 6 (total 54) COMAC CAL s.r.o.
Installation in pipeline
Important information for selection of location
!!! In case of detached design, the cable must not be extended or cut short !!!
Outdoor conditions
It is necessary to ensure that the flow sensor is not exposed to weather effects and that the measured
medium cannot freeze in the flow sensor as it would damage the measuring tube.
In case of outdoor location of the electronic evaluation unit, the manufacturer recommends using a
protective box or a roof to avoid direct solar exposure so that the evaluation electronics cannot get
overheated.
Sources of disturbances
The following items rank among the most frequent sources of disturbances to the steady flow of liquid:
•Abrupt changes in pipe cross-section if not performed as a cone with an angle of 7° (where 
is the angle made by bevelled walls of the pipe reduction).
•Incorrectly centred sealing, low ID sealing or sealing made of soft elastic materials which are
pushed out into the interior pipe cross-section after flanges are tightened.
•Anything interfering in the flow of liquid, for example thermowells, branch pipes, T-pieces, bends,
elbows, slide valves, cocks, flap valves, shut-off valves, control valves, butterfly valves and check
valves. Pipe outlets from tanks, heat exchangers and filters.
•No intensive magnetic fields in the proximity of the induction flow sensor (detector) must be
present.
No sources of disturbances affecting the steady flow must be present in the straight pipeline sections.
They must be located in the piping after the flow sensor or at the farthest distance before it. Sources of
disturbances may substantially reduce the measuring range and accuracy of the flow meters.
Vibration
We recommend supporting the connecting pipes on both sides of the meter for partial elimination of
vibrations. Levels and range of vibrations must be under 2.2 in the frequency range of 20...50 Hz
according to IEC 068-2-34. If the pipeline is exposed to excessive vibrations (e.g. from pumps), using
compact meters is not recommended.
Actual location
The flow sensor (detector) must not be at the top position of the pipe which may be airlocked, or in
declining or even in horizontal pipelines with open ends in which air may penetrate. Impurities may
accumulate during long-term measurement of very low flow rates Q < 0.1 m/sec. There must be a
sufficient pressure in the place of flow sensor installation so that the expulsion of gas or vapour bubbles
from the liquid is avoided. Little bubbles that always occur in liquids may accumulate at any of the
electrodes and this may result in incorrect operation of the meter. Gas bubbles are expelled also at an
abrupt pressure drop. Therefore, butterfly valves and similar elements should be located after the flow
sensor. For the same reason, the flow sensor should not be placed at the suction side of the pump. To
prevent the bubbles from accumulation at a low flow in the flow sensor, it is suitable, e.g. that the pipe
is slightly ascending or that the flow sensor is located in the vertical section of the pipeline.

Manual FLOW 38 Page 7 (total 54) COMAC CAL s.r.o.
If the meter is populated with measuring electrodes only (2 or 3 electrodes located beyond the upper
profile of the tube), it is necessary for proper function of the meter, to fill up the flow sensor with the
fluid to be measured so that erroneous readout of quantity of liquid passing through the meter can be
avoided when the pipe is empty. It is necessary to select the location of the meter in such a way that the
flow sensor aeration can be avoided. In the case of an open system, the flow sensor is placed in the
bottom position of the U-profile pipework, ensuring that the fluid will not flow out of the sensor.
In the case that the sensor is equipped with an empty pipe testing electrode (3rd or 4th electrode in the
upper part f the measuring tube profile), there is no risk of erroneous readout of quantity of liquid passing
through the meter due to aeration of measuring electrodes. This function must be activated in
PARAMETERS (EMPTY TUBE TEST) menu. If it be to the contrary, the same conditions apply as if
the testing electrode is not populated.
The function of empty tube detection in horizontal mounting position
operates correctly only if the evaluation unit is oriented upwards (see Fig.
below). Alternatively, it is not possible to ensurethat the activation of empty
tube detection in case of partly filled or empty pipes will take place.
Due to the principle, it is necessary that the maximum
conductivity of medium is 6000 µS for ensuring the
functional evaluation of empty tube. Beyond this limit, errors
may occur in empty tube test, and in this case, it is necessary
to deactivate the empty tube test. If the conductivity of
medium is beyond the permissible range, the meter may,
despite the flooded system, register empty pipeline and the
measurement will not start.
In case of any intervention into the measuring circuit must be accessed like a pipe is fulfilled of medium,
and regardless of the displayed information “empty pipe test” on the display meter !!!
Installation examples
Trouble-free and exact operation of the meter is dependent on its correct location in the system. The
most frequent methods of the placement are shown in the following figures:
Recommended installation locations Downtake pipe
Install an air bleed valve
after the sensor 
Pipeline is
empty;
erroneous
measurement
Correct
location
Bubbles are accumulated in the
pipeline; erroneous measurement

Manual FLOW 38 Page 8 (total 54) COMAC CAL s.r.o.
Horizontally laid pipeline Long pipeline
Free inlet or outlet Pumps
The flow of liquid flow in the flow sensor should be steady and free of whirling. For this reason,
straight sections of pipeline with the same ID as that of the flow meter before and after the flow sensor
(with permissible deviation of +5%). Recommended minimum length of straight sections is 5d before
the flow sensor and 3d after the flow sensor where d is the inside diameter of the meter in millimetres.
The same principles apply before and after the flow sensor in case of bi-directional flow measurement.
Recommendations
•In case of whirled up flow, extend the calming sections of pipeline or integrate a flow conditioner.
•When blending a mixture of substances, it is necessary to install the flow meter either before the
point of blending or at a sufficient distance after it (30d min. where d is the inside diameter of
the meter in millimetres), otherwise it will result in instability of indication.
•When plastic pipeline is used or in case of metallic pipes with internal non-conductive layer,
earthing rings are needed.
•Do not install the sensor at the suction side of the pumps; this will eliminate the risk of vacuum
and possible damage to the measuring tube lining.
•Pumps, bends and elbows found closely in succession in various levels should be at a distance
of 20d at least before the flow sensor. In case of a separate elbow or bend, the placement 10d
before the meter is recommended.
•When piston pumps, diaphragm pumps, and flexible tube pumps are used, it is necessary to install
a pulse damper in the system.
•In order to provide the highest accuracy, it is important to ensure permanent flooding for the
sensor (for example, by installation of the sensor in the U-shaped pipeline) even if the sensor is
equipped with empty tube test. This will serve as an additional safety measure for detection of
non-flooded tube.
The responsibility for suitability and adequacy of application of induction flow meters is borne by the
designer or possibly the user himself.
Place the sensor in a slightly
ascending pipeline
Install controls and shut-off
valves always after the sensor
Built in the U-shaped pipeline
The flow meter must not be installed
in the suction side of the pump
free flow

Manual FLOW 38 Page 9 (total 54) COMAC CAL s.r.o.
Actual installation in pipeline
When welding both counter-flanges to the pipelines, it is necessary to maintain their alignment so that
levelness of bearing surfaces of the flanges onto the front faces of the detector is ensured (at the same
time, this must not be achieved by unequal tightening of the bolts as there is a risk of leakage due to
thermal loading in the future or the measuring tube may break during such tightening). The difference
of LMAX and LMIN distances of the sealing surfaces of the flanges before the flow sensor is installed
must not be greater than 0.5 mm.
The opposition of the holes in the counter-flanges for the bolts should be ensured in the same manner
and a sufficient room behind the flanges should be available for the bolts and nuts so that the actual
installation of the sensor in pipeline and its attachment with the bolts is made possible.
The manufacturer recommends using an intermediate piece during welding. It is absolutely excluded to
use the flow sensor as an intermediate piece due to thermal damage. The welding current must not run
through the flow sensor during electrical welding. The installation of the flow sensor is carried out after
welding, coating, building and similar works are completed.
The actual installation is performed by the fixation between the counter-flanges that are welded to the
calming pipeline (5×d before and 3×d after in the direction of flow) whereas the liquid must run through
the flow sensor in the direction indicated by the arrow on the sensor name plate.
During installation, do not lift the meter by the evaluation unit housing (in case of detached design, by
the sensor terminal box), possibly under the meter's metallic housing but always use slings round the
process connection or use the lifting lugs on the flanges.
Installation position
The inductive flow sensor is installed in arbitrary position in
vertical piping. In case of horizontal piping, it is necessary to
make sure that the sensor is installed with its measuring
electrodes in horizontal position. In case of the earthing
electrode design, possibly with testing for empty pipeline, then
the installation is always performed with the earthing
reference electrode facing down (with the sensor terminal box,
eventually with the evaluation unit facing upwards). Then the
earthing reference electrode is in the bottom position and the
empty tube sensing electrode is in the top position of the flow
sensor.
Every time when the empty tube testing electrode is not
covered with a liquid for 5sec at least, the flow meter will
display the "Empty tube" status, and if it is necessary, it sends
out an error message and stops taking measurement.

Manual FLOW 38 Page 10 (total 54) COMAC CAL s.r.o.
The measurement accuracy is maintained in this way. Once the electrode is covered with the liquid again,
the error message disappears and the flow meter starts taking measurement again.
Measurement error caused by incorrect mounting installation
1) correct installation (flow sensor should be install in arbitrary position in vertical piping)
EMPTY TEST –ON EMPTY TEST –OFF
2) incorrect installation (placing the unit diagonally, Empty test –ON)

Manual FLOW 38 Page 11 (total 54) COMAC CAL s.r.o.
Installation in piping and placement of measuring electrodes in flow sensor
1) in the version without the earthed reference electrode and/or empty piping test (2 electrodes)
2) in the version with earthed electrode and/or empty piping test electrode (3/4 of the electrode)
During installation, beware of:
-dropping the meter onto the ground and damaging the measuring tube or electronics
-contamination of the electrodes (do not touch the electrodes, otherwise they get contaminated)
-when additional sealing is used, avoid its interference in the flow profile of the detector
between the flanges and the pipeline, otherwise the flow measurement error may be increased

Manual FLOW 38 Page 12 (total 54) COMAC CAL s.r.o.
Tightening torques
It is absolutely necessary to tighten the bolts and nuts equally by alternating sides and in the order
shown in figure applying the maximum torque according to the table.
If the bolts are tightened too much during the installation of pipework components, deformation of the
sealing surface may occur. In consequence, the torque values indicated in the table are used as a
guidance for tightening the screws and bolts.
Table with tightening torques for screws/bolts (EN 1092-1):
Diameter
nominal
PN 10
PN 16
DN
Screws
Tightening torque [Nm]
Screws
Screws
Rubber
PTFE,PFA
ETFE, PVDF
Rubber
PTFE,PFA
ETFE, PVDF
10
4 x M12
10
15
4 x M12
10
15
15
15
20
15
20
20
20
25
20
25
25
20
25
20
25
32
4 x M16
20
25
4 x M16
20
35
40
20
25
20
35
50
20
45
20
45
65
20
46
20
46
80
8 x M16
20
48
8 x M16
20
48
100
20
50
20
50
125
20
80
20
65
150
8 x M20
24
90
8 x M20
27
90
200
27
115
12 x M20
35
80
250
12 x M20
35
95
12 x M24
55
100
300
50
100
80
110
350
16 x M20
60
70
16 x M24
95
105
400
16 x M24
75
120
16 x M27
140
150
500
20 x M24
100
150
20 x M30
250
230
600
20 x M27
165
240
20 x M30
400
360

Manual FLOW 38 Page 13 (total 54) COMAC CAL s.r.o.
Diameter
nominal
PN 25
PN 40
DN
Screws
Tightening torque [Nm]
Screw
Tightening torque [Nm]
Rubber
PTFE, PFA,
ETFE,PVDF
Rubber
PTFE, PFA,
ETFE,PVDF
10
4 x M12
15
15
4 x M12
15
15
15
20
20
25
25
20
25
25
25
25
25
25
25
25
25
32
4 x M16
25
35
4 x M16
25
40
40
25
35
35
50
50
35
45
35
60
65
8 x M16
35
46
8 x M16
45
55
80
40
48
45
60
100
8 x M20
40
55
8 x M20
50
75
125
8 x M24
50
110
8 x M24
70
120
150
57
115
75
136
200
12 x M24
68
100
12 x M27
85
145
250
12 x M27
88
120
12 x M30
105
220
300
16 x M27
95
125
16 x M30
115
250
350
16 x M30
115
200
16 x M33
140
-
400
16 x M33
135
255
16 x M36
165
-
500
20 x M33
350
430
20 x M36
-
-
600
20 x M36
600
740
20 x M45
-
-
In case of using a corundum or thermoplastic tube, the same torques apply as in case of using the PTFE
tube according to the given pressure series.
Threaded connection (EN 10226-1):
Diameter
nominal
DN
Process connection
[inch]
Tightening torque
[Nm]
10
3/8”
8
15
½“
10
20
¾“
21
25
1“
31
32
1 ¼“
60
40
1 ½“
80
50
2“
5
65
2 ½“
6
80
3“
15
100
4“
14
If you do not find your size or structure in the Torque Table, it is a special or non-standard design. In
such a case, contact the manufacturer for more detailed information.

Manual FLOW 38 Page 14 (total 54) COMAC CAL s.r.o.
It is necessary to do the tightening three times, whereas for the first time, to 50% of the maximum torque
according to the above given Table. For the second time, to 80% and for the third time, to 100% of the
maximum torque. We recommend checking the screws/bolts for tightening some 24 hours after
installation of the meter.
When installing the flow sensors over 200 mm, it is necessary to follow, except for the above mentioned
rules, also simultaneous tightening of parallel screws on both opposite flanges to avoid possible
damaging the electrodes or the measuring tube (symmetrical tensioning of the lining).
If the flanged joint is not tight, although all of the screws are tightened closely, these must not be
tightened more but slackened on the opposite side to the untightness and tightened on the other side. If
the untightness manifests itself even after that, it is necessary to check the sealing surfaces for scratches
or mechanical impurities. If the scratches or any other damage are deeper than some 15% of the thickness
of the flange, it is possible to remove them using fine emery paper.
In case of the threaded connection, it is necessary to check, while tightening, the screwed connection on
the sensor so that torsional displacement is be avoided.
Seal
The turned up part of the lining does not carry out the function of sealing so it is necessary to insert the
appropriate seal precisely centred between the sensor and the pipeline. If the sealing extends in some
place into the flow profile, it makes whirls and reduces the measurement quality. Use the seals
compatible with the liquid and 5mm thick. Do not use graphite or any other electrically conductive
material to hold the sealing in place during installation. It could influence the measuring signal accuracy.
Earthing
For reliable and correct operation of the induction sensor it is necessary nto provide proper protective
and working eathing. The earth line must not transmit interference voltages so the other electrical
devices must not be earthed by means of this line.
The flow sensor is provided with the M5 earthing screw of stainless steel with a washer and nut for
proper connection of the sensor body with both counter-flanges of the metallic pipeline. The earthing
cable lug is screwed there and it should be conductively connected with the counter-flanges. On the
counter-flanges, it is recommended their connection to the welded crews or into a threaded hole.
Connecting under the fixing screws of the flange is not suitable as they may corrode with time and cause
failures in measurement.
However, if it is not ensured that the counter-flanges are in dicert contact with the measured media and
they are conductive, the earthing rings must be used, refer hereinafter.

Manual FLOW 38 Page 15 (total 54) COMAC CAL s.r.o.
Earthing rings
Using for a plastic pipeline or in case of metallic pipelines with internal plastic lining turned up or pulled
out to the front faces of the pipeline flanges. Conductive earthing rings of stainless steel create
conductive connection with the measured substance. Usually, potential equalization is carried out by
means of the reference earthing electrode in the measuring tube. In exceptional cases, the equalizing
currents may run through the reference electrode based on the device earthing conception. This may lead
to deterioration of the sensor, e.g. by electrochemical disintegration of the electrodes. In such cases, it is
necessary to use the earthing rings for potential equalization. This holds true for two-phase or two-
component flows in which the medium is blended badly or its components cannot be blended. In general
it can be said that using the earthing rings is always the protection against stray currents and the warranty
of correct measurement at the same time.
The flow sensor is provided with the earthing screw of stainless steel for the earthing cable supplied with
the mounting accessories. Then this cable must be conductively connected with the earthing rings.
The earthing rings are not part of our standard package and must be ordered separately. Chemical
durability of the material must correspond with the liquid to be measured; it is usually made of the same
material as the sensor electrodes. While mounting, it is necessary to insert seals in both sides of the
earthing ring and take care that no part extends to the internal profile of the sensor (whirling and
turbulence of the medium).

Manual FLOW 38 Page 16 (total 54) COMAC CAL s.r.o.
Electrodes
The electrode material must be selected according to chemical resistance to the liquid to be measured.
The purity of the electrodes may have an influence on measurement accuracy, their heavy foulness may
cause even the interruption of the measuring function (isolation from the liquid). It is not necessary to
clean the electrodes right after delivery before their installation in the pipeline. If the electrodes indicate
signs of foulness, clean them with a soft cloth or use a chemical cleaning agent. Mind damaging to the
lining! During routine operation, in case of a great majority of liquids, it is not necessary to clean the
flow meter for the entire operation period of the flow sensor; self-cleaning by flow of the liquid is
sufficient (recommended velocity is over 2 m/sec).
PTFE, PFA, EFTE lining
Meters with PTFE lining are equipped with protective covers to prevent the sealing surfaces from
damaging during transportation or storage and from changing the shape (due to elastic memory of the
PTFE material, it is restraightened to the tube). Protective covers may be removed only right before the
installation. If these covers are removed due to a check, it is necessary to replace them immediately.
Carry out the installation at the lowest point of the pipeline to avoid the occurrence of vacuum. Never
detach and damage the rim of the PTFE lining turned up to the of flow sensor faces. Remove the covers
from the inlet and outlet sides right before insertion of the sensor between the pipeline flanges and
replace them with metal plates (0.3...0.6 mm thick). After insertion of the sensor, remove the metal plates
and install the screws/bolts.
High temperature pipeline
High temperature medium
At temperatures of the medium to be measured over 100°C, it is necessary to compensate the forces
caused by thermal expansion of the pipeline dueto its temperature rise. For short pipelines, it is necessary
to use flexible seals, for long pipelines, use flexible pipe elements (e.g. bends).
The flow sensor must never by thermally insulated. In case that the sensor is placed in a thermally
insulated pipeline, the thermal insulation must be interrupted and the flow sensor is installed without
thermal insulation.
When a compact meter is used (evaluation unit placed on the sensor body), it is necessary to respect the
temperature of medium up to 90 °C. In case of exceeding this temperature, the correct functionality of
the electronic evaluation unit is not guaranteed, or there is a risk of its destruction.
Installation check
After installation of the flow sensor in the pipeline, the following must be checked:
-According to the name plate, if there is a relevant meter in the given measuring point (pressure,
temperature, dimension, etc.).
-If the direction of the arrow on the device is in agreement with the direction of the flow in the
pipeline.
-Correct position of the measuring electrodes (horizontally).
-Correct position of the electrode for empty pipeline detection (up).
-If all bolts (screws) are tightened properly.
-If earthing rings are used, then their correct installation and connection with the sensor.
-Accuracy of flow sensor earthing.
-Accuracy of execution of the pipeline calming section lengths
-If the sensor is protected against vibrations and mechanical damage.
-If the name plate (serial number) on the sensor corresponds to the one on the electronics.

Manual FLOW 38 Page 17 (total 54) COMAC CAL s.r.o.
Wiring
Workers performing wiring are subject to the requirements of Decree No. 50/1978 Coll. on activities on
electrical equipment!!! When the operations described below are performed unprofessionally, the claim
on warranty becomes extinct!!! Prior to any opening of the evaluation unit, switch off the power!!! It is
necessary to bear in mind that in case of detached design, the electronic evaluation unit and the flow
sensor form an integral unit which is calibrated and matched uniquely. In consequence, make sure that
the serial numbers of both parts are always identical!!!
Important information
Flow sensor connecting cable
The signal cable of the detached induction flow sensor cannot be led in parallel (even partly) with the
cables for power distribution voltage or in the proximity to electric motors, electromagnets, contactors,
frequency converters and similar sources of electromagnetic interference. In unavoidable situations, it is
necessary to put the cable in an earthed iron tube. Primarily in media with a low conductivity, cable
movements and interference may result in distortion of the measured signal. The maximum length of the
cable between the sensor and the evaluation unit is 30 metres provided that the conductivity is over
50µS/cm. In case of lower conductivities, it is recommended to use the shortest possible cable length,
however, 10m max.
In case of detached designs, it is possible to interconnect only the sensor and the transducer with the
same serial numbers. The special cable for connection of the detached meter design must not be extended
or cut short. In case of infringement of these requirements, measurement failures and significant
inaccuracies may occur once the meters are connected.
If it is possible to expect an increased level of unwanted electromagnetic field, we do not recommend
using the detached design. In places with strong electromagnetic interference (in the proximity of
frequency converters, electric motors, transformers, etc.), we recommend putting a line filter before the
meter in the power supply circuit.
Evaluation unit
As standard, the evaluation unit is delivered for mains power supply 230V / 50...60Hz.
It is possible to specify also DC power (as standard, 24V AC/DC / 250mA).
For securing the tightness of the evaluation unit cover, it is necessary to keep the seal intact and clean
(replace the damaged seal immediately). If the holes for cable entries are not occupied, it is necessary to
do it.
The flow meter signal outputs may only be connected to devices where accident protection is provided
by a safe low voltage and where generated voltages do not exceed the limits defined for safe low voltage.
In case of mains power 230V / 50...60Hz, the meter is fed by a switched power supply which may contain
beats in acoustic spectre whereas this symptom does not indicate a failure of the meter.
Never make kinks on the cable and on individual conductors and do not let them cross mutually in the
terminal board area and always use a separate cable grommet for power supply.
Cover the unoccupied grommets with a piece of cable or a plastic plug (securing of tightness).

Manual FLOW 38 Page 18 (total 54) COMAC CAL s.r.o.
Installation of the meter's detached evaluation unit
The design HEAD (H) –it is a standard design with a possibility of installation both in compact and
detached designs (as per purchase order)
Firstly decide if you want to install the fixing bracket behind, or under the electronics (the bracket with
holes upward or downward). Install the fixing bracket on the meter's aluminium housing; place the unit
as required on the wall or on a structure and mark the holes in this position for the attachment of the
bracket. Unscrew the bracket and attach it to the marked location, e.g. using wall plugs and screws.
Screw down the electronics on to the fixing bracket and connect the sensor cable using the connector.
Attach the cable to the wall or to the structure so that it does not "dangle" from the connector. Make a
"drip loop" downwards so that water cannot trickle onto the connector. Fix the conductors for power and
the outputs in a similar way. After installation of all cables, turn the electronics to the required position
and fix the unit to the bracket by tightening the fastening nut.
The FRONT (F) design –this design can be positioned again as the compact or detached ones
Wall mounting:
At first, unscrew the DIN rail holder from the unit by slackening two screws from the bottom of the box.
After that, attach the unit without the top cover to the wall into the desired position and mark the internal
holes (in corners of the 63x145mm rectangle). Drill the holes and put in the wall plugs, use the screws
to fix the unit to the wall and connect the flow sensor cable using the connector. Attach the cable to the
wall or to the structure so that it does not "dangle" from the connector. Make a "drip loop" downwards
so that water cannot trickle onto the connector. Fix the power conductors (possibly outputs) in a similar
way and complete the installation by closing the unit with the cover and tightening it.
Din rail installation:
Installation is carried out by locking the holder located on the bottom part of the unit into the DIN rail.
After that, connect the connector of the flow sensor cable with the power cable (possibly outputs) and
close the unit with the cover and tighten it in a similar way as in the case of wall mounting.

Manual FLOW 38 Page 19 (total 54) COMAC CAL s.r.o.
The PANEL (P) –this design is modified for building in panel areas, ideally into door, etc. where
Built-in installation is desirable.
The installation of the evaluation unit is carried out by cutting a 110x110mm square opening with an
overall area considered for the 140x140mm unit. Remove the square frame from the unit whereas the
sealing is left on the unit. After pulling the unit through the installation opening, put on the frame from
the rear side and tighten it with four inserted screws in the lateral holes so that the unit is stabilized and
prevented from a possible displacement.
*The necessary mounting depth, including the cable connector from the flow sensor is 200mm.
Meter wiring
The evaluation unit consists of two assemblies:
Front PCB with display unit Input/Output PCB along with power supply
Evaluation unit terminal board wiring:
Terminals No. 1, 2 current output 4…20 mA
Terminals No. 3, 4 OUT1-Imp/Flow switch
Terminals No. 5, 6 RS485 communication
Terminals No. 7, 8 OUT2-Imp/Flow switch/Status
Terminals No. 9,10 reset Total V register (resettable counter) by external button
Terminals No.11,12 output voltage 16 V/100 mA (power supply for changing to active current
and impulse outputs)
Terminals L, N, PE mains voltage 230 VAC (standard), available also in 24 VAC/VDC version
which does not matter on the polarity of the power connection.
(Install as an independent supply circuit with its own protection 0.5…1 A)
Note: Terminal board and jumper connection is always indicated on the power supply cover sheet and
on the rear cover.

Manual FLOW 38 Page 20 (total 54) COMAC CAL s.r.o.
OUT1 / OUT2
Impulse outputs / FlowSwitch / Status
OUT1 and OUT2 outputs are freely configurable and implemented by the optocoupler with an NPN
switching transistor. Limit parameters of this optocoupler are 80V/50mA/100mW max. The output can be
connected as a passive one or active one when terminals 11 and 12 are used. In active mode, the meter makes
use of its internal galvanically separated 16V power supply. In this case, the switch voltage for logical high
is 16V with the recommended current consumption of approx. 2mA with regard to optocoupler transfer. The
output in off-state is found in high impedance state and so it is necessary to use a pull down or pull up
resistors for defining the steady-state level.
Configuration:
1) The Impulse output is used for remote transmission of volumetric impulses. The conversion constant is
arbitrarily variable using buttons or user software. The adjustment must be carried in such a manner that the
frequency at maximum flow rate fout<400Hz.
2) The FlowSwitch is used for flow rate value monitoring. When the set limit flow rate is exceeded, the
contact will be switched (contact making/breaking). The level of contact making and contact breaking is
different –the contact has hysteresis The hysteresis is adjustable in %.
3) The Status output is used for evaluation of meter’s status – failure, warning, failure+warning.
Wiring connection examples –passive output: Terminal board wiring
connection:
Examples of connection –active output: Terminal board connection:
Due to CTR≈100% and If=2.5mA, it is suitable to select collector current up to 2.5mA.