Schmidt SS 23.700 Ex User manual

SCHMIDT®Flow Sensor
SS 23.700 Ex
Instructions for Use

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 2
SCHMIDT®Flow Sensor SS 23.700 Ex
Table of Contents
1Important information.......................................................................3
2Application range - General.............................................................4
3Application range - ATEX................................................................6
4Mounting instructions - General ......................................................7
5Mounting instructions - ATEX........................................................17
6Electrical connection - General .....................................................19
7ATEX - Electrical connection and protective sleeve assembly .....24
8ATEX type plate - Labelling...........................................................26
9Signaling........................................................................................27
10 Commissioning..............................................................................32
11 Information concerning operation..................................................32
12 Service information........................................................................33
13 Dimensions....................................................................................36
14 Technical data ...............................................................................37
15 Declarations of conformity.............................................................39
16 Type Examination Certificate ........................................................41
Imprint:
Copyright 2023 SCHMIDT Technology GmbH
All rights reserved
Version: 570454.02
Subject to modifications

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 3
1 Important information
The instructions for use contain all required information for a fast commis-
sioning and a safe operation of SCHMIDT®flow sensors.
These instructions for use must be read completely and observed care-
fully, before putting the unit into operation.
Any claims under the manufacturer's liability for damage resulting from
non-observance or non-compliance with these instructions will become
void.
Tampering with the device in any way whatsoever - with the exception
of the designated use and the operations described in these instructions
for use - will forfeit any warranty and exclude any liability.
The unit is designed exclusively for the use described below (refer to
chapter 2). In particular, it is not designed for direct or indirect protection
of personal or machinery.
SCHMIDT Technology cannot give any warranty as to its suitability for
a certain purpose and cannot be held liable for errors contained in these
instructions for use or for accidental or sequential damage in connection
with the delivery, performance or use of this unit.
Symbols used in this manual
The symbols used in this manual are explained in the following section.
Danger warnings and safety instructions. Read carefully!
Non-observance of these instructions may lead to injury of the
personal or malfunction of the device.
Risk of explosion - Read carefully!
Important instructions for use in areas subject to explosion haz-
ards.
General note
All dimensions are given in mm.

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 4
2 Application range - General
The SCHMIDT®Flow Sensor SS 23.700 Ex (art. no.: 569700) is designed
for the stationary measurement of flow velocity as well as the temperature
of air and gas with operating temperature from -20 … +120 °C and working
pressure
1
up to 16 bar.
The sensor is based on the measuring principle of a thermal anemometer
and measures the mass flow of the measuring medium as flow velocity
which is output in a linear way as standard velocity
2
wN(unit: m/s), based
on standard conditions of 1013.25 hPa and 20 °C. Thus, the resulting out-
put signal is independent of the pressure and temperature of the medium
to be measured.
When using the sensor outdoors, it must be protected against di-
rect exposure to the weather.
Version “PWIS-compliant”
It differs from the standard version in the following points:
Use of a special PWIS-compliant compression fitting (abbr.: DGV),
completely made of stainless steel, which seals by means of a cutting
ring (i.e. there is no O-ring or other plastic in contact with the medium).
The cutting ring is designed relatively "soft" so that it does not bite too
much when tightened and can therefore be easily loosened again, mak-
ing it unnecessary to use a lubricant. The internal thread of the com-
pression nut is finished with a coating (DURNI-COAT®) which prevents
jamming.
The packaging (foil pouch) of the sensor is also PWIS-compliant.
In addition, the sensor, together with its supplied mounting accessories
(pressure safety kit) and optional accessories, is specially cleaned in
accordance with the IEC/TR 60877:1999 standard.
The PWIS-compliant zone is limited to the actual sensor probe part only!
Only the tube-shaped probe itself (incl. its DGV and pressure
protection components) is PWIS-compliant.
By opening the shipping package, the customer assumes respon-
sibility for maintaining or restoring the PWIS-compliance of the
probe as well as the cleanliness of the rest of the sensor and its
accessories in accordance with IEC/TR 60877:1999.
1
Overpressure
2
Corresponds to the actual velocity under standard conditions

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 5
Information concerning PWIS-compliant handling
In general, it is essential to avoid contamination, especially of the PWIS-
compliant sensor component:
- Before installing the sensor, carefully clean its mounting location.
- Make sure to use only clean tools and material for the installation.
- Before opening the packaging foil, remove dirt such as dust from its sur-
face, if necessary.
- If possible, open the packaging film and take out the sensor directly at
the installation site.
- Otherwise open the package foil at an appropriate and clean workplace
and store the sensor in an appropriate, PWIS-compliant container.
- Don’t touch the PWIS-compliant sensor parts with bare hands.
- Use clean and non-fluffy gloves or cloths or similar to handle the sensor,
preferably in PWIS-compliant models.
Version for “special gases”
The version of the SS 23.700 Ex for “special gases” receives a gas-spe-
cific adaption for the measurement of certain gases and gas mixtures.
The sensor is adjusted and calibrated in air. Then a special correction
function for the medium to be measured is applied to the sensor. This cor-
rection has been determined for many gases in real gas ducts. For gas
mixtures, the correction adaption is calculated according to the volume
based mixing ratio.
Mechanical versions
The sensor SS 23.700 Ex is available in two mechanical versions:
- Compact sensor:
The sensor probe is fixed to the main enclosure.
- Remote sensor:
The sensor probe is mechanically separated from the main enclosure.
Connection is realized by an electrical signal cable that cannot be de-
tached on either side.
The different construction types and their dimensions can be found in the
dimensional drawings in chapter 13.
The customer is responsible for observing all relevant statutory
provisions, standards and directives relating to the use of gases.

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 6
3 Application range - ATEX
As a category 3 device, the SCHMIDT®Flow Sensor SS 23.700 Ex is
equipped with the following types of protection:
o Gases (Zone 2): II 3G Ex ec ic IIC T4 Gc
o Dusts (Zone 22): II 3D Ex ic tc IIIC T135°C Dc
The sensor is only suitable for use in combustible, conductive
dusts with a smoldering temperature higher than 210 °C.
Special conditions for use ("X"):
o The internal intrinsically safe circuit is isolated
3
from the en-
closure only up to 30 V.
o A power supply with protection class III is required (PELV).
o The permissible pulling force at the connecting cable of the
remote version is limited to 20 N (25 % of the nominal value
of the standard according to Annex A, chapter A.2.3.2).
The permissible operating temperatures are:
o Electronics: -20 ... +70 °C
o Sensor probe (medium): -20 ... +120 °C
Electrical data:
o Rated voltage: 24 VDC ± 20 %
o Rated current: 250 mA
o Measurement outputs: 0 … 10 V / 4 … 20 mA
o Impulse output: f = 0 … 100 Hz
Umax = 28.8 VDC
Imax = 100 mA
o Relay output: f = 0 … 100 Hz
Umax = 30 VDC
Imax = 50 mA
Enclosure:
o Degree of protection: IP66 (main enclosure)
IP67 (sensor probe)
3
Limitation by varistor inside the sensor between GND and enclosure (ESD-protection).

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 7
4 Mounting instructions - General
Handling
The flow sensor SS 23.700 Ex is a precision instrument with high meas-
uring sensitivity. In spite of the robust construction of the sensor head,
soiling of the sensor elements can lead to distortion of measurement re-
sults (see also chapter 12).
During procedures such as transport, installation or dismounting of the
sensor that facilitates soiling as well as represent a mechanical load on
the sensor head, the protective cap supplied by SCHMIDT Technology
should generally be attached to the sensor head and only removed during
installation.
To avoid soiling and mechanical stress on the sensor head, the
protective cap should be placed over it during transport or instal-
lation.
Mounting method
The sensor SS 23.700 Ex can be mounted only by means of a compres-
sion fitting which supports the sensor tube and ensures frictional clamping.
The compression fitting as well as a pressure protection kit is included in
the scope of delivery.
Due to the variety of applications the compression fitting exists in different
versions. On the one hand they are determined by the design of the ex-
ternal thread (order option: G½ or R½), on the other hand by the materials
and properties of the sealing:
Standard: Sealing with O-Ring (NBR)
PWIS-compliant: Sealing with clamping ring (stainless steel), only G½
Systems with overpressure
The SS 23.700 EX is designed for a maximum working pressure of 16 bar.
As long as the medium to be measured is operated with overpressure,
make sure that:
There is no overpressure in the system during mounting.
Mounting and dismounting of the sensor can be carried out
only as long as the system is in a depressurized state.
Only suitable pressure-tight mounting accessories are used.
Appropriate safety measures are installed to avoid unintended discard-
ing of the sensor due to overpressure. If other accessories than the de-
livered pressure protection kit or alternative mounting solutions are
used, the customer must ensure the corresponding safety measures.

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 8
For measurements in media with overpressure, appropriate
safety measures must be taken to prevent unintended discard-
ing of the sensor.
The pressure-tight mounting, the fastening of the screw pipe
connection and the discarding protection must be checked be-
fore pressure is applied. These tightness checks must be re-
peated at reasonable intervals.
The components of the pressure protection kit (bolt, chain and
bracket) have to be checked regularly for integrity.
Thermal boundary conditions
In the case of medium temperatures that don’t correspond to the permis-
sible operating temperature of the electronics, cross-talk of the tempera-
ture into the electronics housing must be prevented by a thermal decou-
pling section of the sensor tube having a free-standing length of at least
50 mm (see Figure 4-1) or by means of other suitable measures.
Figure 4-1
The permissible operating temperature range of the electronics
must not be exceeded by crosstalk of the medium temperature on
the sensor housing.
Flow characteristics
Local turbulences of the medium can cause distortion of measurement
results. Therefore, appropriate mounting conditions must be guaranteed
to ensure that the gas flow is supplied to the sensor in a laminar
4
state,
i.e. quiet and low in turbulence. The corresponding measures depend on
the system properties (pipe, chamber, etc.) which are described in the fol-
lowing subchapters for different mounting variants.
Correct measurements require a (laminar) flow, low in turbulence.
4
The term “laminar” means here an air flow, low in turbulence (not according to its physical
definition saying that the Reynolds number is < 2300).
> 50 mm
2

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 9
Installation conditions
The sensor head of the SS 23.700 Ex consists of two basic elements:
Heater
The longer of the two sensor tubes at the tip of the sensor head is the
so-called heater. It consists of a heated, temperature-dependent resis-
tor that is used to measure flow velocity.
The end of the heater element, to which the length specification (L) of
the sensor also refers, represents the actual measuring point of the flow
measurement and should be placed as favourably as possible in the
flow, e.g. in the middle of the pipe.
Temperature sensing element
The shorter of the two sensor tubes at the tip of the sensor head is the
temperature sensor. It consists of an unheated, temperature-dependent
resistor, which measures the temperature of the medium.
The aerodynamically optimized design allows tilting around the longitudi-
nal axis of the sensor up to ±3° relative to the ideal measuring direction
(see Figure 4-2) without significant impact on the measurement result
5
.
The axial tilting of the sensor head relative to flow direction should
not exceed ±3°.
Position the sensor head always at the most advantageous posi-
tion for flow measurement.
The sensor measures unidirectional (see “flow arrow” in Figure
4-2) and must be adjusted correctly relative to the flow direction.
View on probe head View on enclosure cover
Figure 4-2 Alignment of sensor relative to flow direction
5
Deviation < 1 % of measured value
Alignment plane

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 10
Mounting in pipes with circular cross-section
Typical applications for this type are compressed air networks or burner
gas supply lines. They are characterized by long thin pipes with a typically
quasi-parabolic flow profile.
The easiest method to achieve a low-turbulence flow is to provide a suffi-
ciently long and absolutely straight distance without disturbances (such as
edges, seams, bends etc.) in front (inlet) and behind the sensor (outlet)
(see installation drawing Figure 4-3). It is also necessary to pay attention
to the design of the outlet distance because the flow is also influenced by
disturbances generating turbulences against the flow direction.
Figure 4-3
L1
Length of run-in distance
L2
Length of run-out distance
D
Inner diameter of measuring distance
The absolute length of the respective distances are determined by the in-
ner diameter D of the pipe because the flow abatement effect depends
directly on the aspect ratio of measuring distances to the diameter. There-
fore, the required abatement distances are specified as a multiple of the
inner pipe diameter D. Besides, the degree of turbulence generation by
the corresponding disturbing object plays an important role. A slightly
curved bend directs the air with a relative low-disturbance level, whereas
a valve generates massive turbulences with its abrupt change of the flow-
guiding cross-section, requiring a relatively long distance for abatement.
The following Table 1 shows the required straight pipe lengths depending
on the inner tube diameter D and different causes of disturbances.
This table lists the minimum values required in each case. If the listed
straight pipe lengths cannot be achieved, measurement accuracy may be
impaired or additional actions are required like the use of flow rectifiers
6
.
6
E.g., honeycombs made of plastic or ceramics.
Run-in distance L1
Run-out distance L2
Ø D

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 11
Flow obstacle upstream of measuring distance
Minimum distance length of
Run-in (L1)
Run-out (L2)
Light bend (< 90°)
10 x D
5 x D
Reduction
expansion
90° bend
T-junction
15 x D
5 x D
Two 90° bends in
one plane
(2-dimensional)
20 x D
5 x D
Two 90° bends
with 3-dimensional
change in direction
35 x D
5 x D
Shut-off valve
45 x D
5 x D
Table 1 Run-in and run-out distances
The profile factors specified in Table 2 may become void by the use of
flow rectifiers.
Calculation of volume flow
Under the conditions described previously, a quasi-parabolic velocity pro-
file forms over the pipe cross-section, whereby the flow velocity at the pipe
walls remains practically zero and reaches its maximum wNin the center
of the pipe (the optimum measuring point). This measured variable can be
converted into an average flow velocity
N
w
that is constant over the pipe’s
cross-section using the so-called profile factor PF.
The profile factor depends on the inner pipe diameter
7
(see Table 2).
7
Both inner air friction and sensor locking are responsible.

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 12
PF
Pipe Ø
Volume flow [m3/h]
Inner
Outer
Min. @
@ Sensor measuring range
[mm]
[mm]
0.2 m/s
10 m/s
20 m/s
60 m/s
90 m/s
140 m/s
220 m/s
0.748
39.3
44.5
0.7
32.7
65.3
196.0
294.0
457.3
718.6
0.772
51.2
57.0
1.1
57.2
114.4
343.3
515.0
801.1
1258
0.786
70.3
76.1
2.2
109.8
219.7
659.0
988.5
1537
2416
0.797
82.5
88.9
3.1
153.4
306.8
920.3
1380
2147
3374
0.804
100.8
108.0
4.6
231.0
462.0
1385
2078
3233
5081
0.812
125.0
133.0
7.2
358.7
717.5
2152
3228
5022
7892
0.817
150.0
159.0
10.4
519.8
1039
3118
4677
7276
11434
0.829
206.5
219.1
20.0
999.5
1999
5997
8995
13993
21989
0.835
260.4
273.0
32.0
1700
3201
9605
14408
22412
35219
0.840
309.7
323.9
45.6
2278
4556
13668
20502
31892
50116
0.841
339.6
345.6
54.8
2742
5484
16454
24681
38393
60331
0.845
388.8
406.4
72.2
3611
7223
21669
32504
50562
79455
0.847
437.0
457.0
91.5
4573
9146
27440
41160
64027
100614
0.850
486.0
508.0
113.5
5676
11353
34059
51088
79471
124883
0.852
534.0
559.0
137.4
6869
13738
41216
61824
96170
151125
0.854
585.0
610.0
165.3
8263
16526
49580
74371
115688
181796
0.860
800.0
311.2
15562
31124
93373
140059
217870
342368
0.864
1000
488.6
24429
48858
146574
219861
342006
537438
0.872
1500
1109
55474
110948
332845
499268
776639
1220433
0.877
2000
1983
99186
198372
595118
892677
1388609
2182100
Table 2 Profile factors and volume flows of different pipe diameters
Thus, it is possible to calculate the standard volume flow of the medium
using the measured standard flow velocity in a pipe with known inner di-
ameter:
AwV
wPFw
DA
NN
NN




2
4

D
Inner diameter of pipe [m]
A
Cross-section area of pipe [m2]
N
w
Flow velocity in the middle of pipe [m/s]
N
w
Average flow velocity in pipe [m/s]
PF
Profile factor (for pipes with a circular cross-section)
N
V

Standard volume flow [m3/s]
SCHMIDT Technology provides a "flow calculator" on its homepage for
the calculation of flow velocity or volume flow in (circular) pipes or (rectan-
gular) ducts for the different sensor types:
www.schmidt-sensors.com or www.schmidttechnology.de

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 13
Installation in systems with square cross-section
For most applications, two limit cases can be distinguished with regard to
flow conditions:
Quasi-uniform flow field
The lateral dimensions of the flow-guiding system are approximately as
large as its length in the flow direction and the flow velocity is small so
that a stable trapezoidal
8
speed profile of the flow is formed. The width
of the flow gradient zone at the wall is negligible in relation to the cham-
ber width so that a constant flow velocity can be expected over the
whole chamber cross-section (in this case the profile factor is 1). The
sensor must be mounted here so that its sensor head, located at a suf-
ficient distance from the wall, measures in the area with the constant
flow field.
Typical applications are:
oExhaust ventilation ducts for drying processes
oChimneys
oOpen spaces (e. g. clean room)
Quasi-parabolic flow profile
The system length is large compared to the cross-section surface and
the flow velocity is so high that the ratios correspond to that of the cir-
cular pipe. This means that the same requirements apply here to the
installation conditions.
Since the situation is similar to that in a pipe
9
, the volume flow in a
square chamber can be calculated by equating the hydraulic diameters
of both cross-section forms.
A rectangular duct (see Figure 4-4) has a hydraulic “pipe diameter” DH:
bR: Width of rectangular channel
hR: Height of rectangular channel
DH: Hydraulic pipe diameter

󰇛󰇜 󰇛󰇜 
Figure 4-4
8
A uniform flow field prevails in the largest part of the space cross-section.
9
The profile factors are equal for both cross-section forms.

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 14
According to this, the volume flow in this duct is calculated as:



        
 
󰇗   󰇡
󰇢
bR/ hR
Width / height of square duct [m]
DH
Hydraulic inner diameter of duct [m]
AH
Cross-section area of equivalent pipe [m2]
N
w
Maximum flow velocity in the middle of duct / pipe [m/s]
N
w
Average flow velocity in pipe [m/s]
PF
Pipe profile factor
N
V

Standard volume flow [m3/s]
Typical applications are:
oVentilation ducts
oExhaust air ducts
Mounting with compression fitting
The compression fitting is mounted using its external thread (G½ or R½).
Typically, a bushing (sleeve) is welded as a fitting onto a bore in the me-
dium-guiding system wall. In most applications, latter are pipes which are
taken as an example for describing the mounting procedure below (details
see Figure 4-5).
Figure 4-5
L
Probe length [mm]
DO
Outer diameter of pipe [mm]
SL
Length of weld-in sleeve [mm]
E
Sensor tube setting length [mm]
AL
Projecting length [mm]
R
Reference length [mm]
Ø DO
AL
DA/2
SL
L
36
R
E
54
2

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 15
Installation process:
Depressurize the system for measurements with overpressure
media and mount the pressure protection kit.
Drill a mounting bore in pipe wall.
Weld pipe sleeve with an internal thread G½ or R½ on to the pipe, in
the center above the mounting bore.
Recommended length of sleeve: 15 ... 40 mm
Plug holding bracket of pressure protection chain into thread of the
compression fitting.
Screw threaded part of compression fitting tightly into the pipe sleeve
(hexagon AF27).
Observe correct seat and alignment of chain bracket.
Check if there is an O-ring seal available and if it is fitted tightly.
Unscrew spigot nut of compression fitting so that the sensor probe can
be inserted without jamming.
Remove protective cap from sensor head. Carefully insert sensor into
the duct of the compression fitting so that the end of the heater (longer
tube) is positioned in the middle of the pipe.
Adjust sensor manually at sensor enclosure by turning it counterclock-
wise by approx. 80° to flow direction (observe flow arrow on enclosure
cover). Make sure that immersion depth is maintained.
Tighten spigot nut slightly by means of a key wrench (AF24) to fasten
the sensor.
Apply a key wrench (AF27) to hexagon bolt of the compression fitting
to lock it. Use another key wrench (AF24) to tighten spigot nut of the
compression fitting until the arrow on the sensor enclosure complies
with the direction of the pipe flow.
Check the set angular position carefully, for example by placing a bub-
ble level on resp. at the alignment plane of the sensor enclosure.
The angular deviation should not be more than 3°, related to
the ideal measuring direction. Otherwise, measurement accu-
racy may be affected.
In case of wrong adjustment, the compression fitting has to be loosened
and the alignment procedure must be repeated.
Shorten safety chain by removing superfluous chain links so that the
chain is slightly tensioned after being locked at the enclosure. Finally,
secure chain with a its padlock.
General note:
Do not use the alignment plane of the enclosure for mechanical
adjustment, e.g. for locking. There is risk of damage to the sensor.

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 16
Mounting of remote version
The sensor probe of the remote version is mounted with a compression
fitting in the same way as the compact sensor.
A wall mounting bracket is provided for fastening the sensor enclosure.
Accessories
The accessories required for mounting and operation of the SCHMIDT®
Flow Sensor SS 23.700 Ex are listed in Table 3 below.
Type / Art. no.
Drawing
Assembly
Connecting cable
Standard with
fixed length:
5 m 524921
- Threaded ring, knurl
- Plug injection-moulded
- Material:
Brass, nickel-plated
PUR, PVC
Connecting cable
Standard10 with
optional length:
x m 524942
- Threaded ring, knurl
- Material:
Brass, nickel-plated
Polyamide, PUR, PP
Halogen-free11
Sleeve12
a.) 524916
b.) 524882
- Internal thread G½, R½
- Material:
a.) Steel, black
b.) Stainless steel 1.4571
Table 3 Accessories
Informations about further accessories for mounting and display are avail-
able on the SCHMIDT®homepage:
www.schmidt-sensors.com or www.schmidttechnology.de
10
Shielded, but shield not connected to cable socket.
11
According to IEC 60754
12
According to EN 10241; must be welded.
L=5m
14,5
5,1
42
L=XXm
20
54
5,9
26,6
34
Rp 1/2

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 17
5 Mounting instructions - ATEX
Prior to installation in potentially explosive atmospheres, the following
safety measures must be observed:
Check if the device category corresponds to the specified
zones.
Check if the operation approval of the operator is available.
Check if there is no explosive atmosphere during assembly,
maintenance or other activities.
Compliance with the applicable regulations and the entire rele-
vant documentation for this device.
ATEX-relevant operating conditions
Pressure-tight accessories
Only use suitable, pressure-tight accessories if media separation
is required.
Observe pressure safety measures.
Opening of enclosure
It is not allowed to open the enclosure (sealed housing screws).
Unauthorized opening of the enclosure renders the explosion
protection null and void!
Remote version
The connecting cable between sensor probe and main enclosure
comprises intrinsically safe circuits. It is connected by the factory
and must not be disconnected or modified in any way.
Mounting of earth or equipotential bonding conductor
The metallic enclosure of the sensor must be connected electrically to
earth or an equipotential bonding according to EN 60079-0.
The cable required for this must be fastened at the terminal screw of the
enclosure, for the remote version at the sensor probe additionally.
In general the following applies to grounding:
The external ground connections of the enclosure must be con-
nected to the equipotential bonding of the hazardous area with
low ohmic resistance.
No equipotential current must flow between the hazardous
area and non-hazardous area.
Minimum cable cross-section: 1 x 4 mm2
The screw must be tightened firmly at the terminal so that the
conductor cannot be loosened or twisted.

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 18
The potential difference between the GND of the operating
voltage and the earth potential13 must be ≤ 30 VPeak.
Figure 5-1 Grounding contacts (red), remote version
Figure 5-2 Grounding contacts (red), compact sensor
13
Limitation by varistor inside the sensor between GND and enclosure (ESD-protection).

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 19
6 Electrical connection - General
The sensor is operated via a plug connector which is integrated in the
enclosure (pin assignment see Table 4), with the following data:
Number of connection pins: 8 (plus shield connection at the metallic enclosure)
Type: M12, A-coded, male
Fixation of connecting cable: M12 thread (spigot nut at connecting cable)
Type of protection: IP67 (with screwed cable)
Model: Binder, series 763
Pin numbering:
View on connector of sensor
Figure 6-1
Pin
Name
Function
Wire color
1
Pulse 1
Output signal: Flow / volume (digital: PNP)
White
2
UB
Operating voltage: +24 VDC ± 20 %
Brown
3
Analog TM
Output signal: Temperature of medium (Auto-U/I)
Green
4
Analog wN
Output signal: Flow velocity (Auto-U/I)
Yellow
5
AGND
Reference potential for analog outputs
Gray
6
Pulse 2
Output signal: Flow / volume (digital: relay14)
Pink
7
GND
Operating voltage: Ground
Blue
8
Pulse 2
Output signal: Flow / volume (digital: relay13)
Red
Shield15
Electromechanical shielding
Meshwork
Table 4
The specified wire colors are valid when one of the SCHMIDT®connecting
cables is used (see subchapter Accessories, Table 3).
The analog signals have an own reference potential “AGND”.
Make sure that no supply voltage is active during electrical instal-
lation and that it cannot be switched on inadvertently.
The metallic sensor enclosure is indirectly coupled to GND (varistor
16
, in
parallel to 100 nF) and has to be grounded, as well as the sensor probe
of the remote version (for details refer to chapter 7).
The appropriate protection class III / PELV (acc. to EN 50178) has
to be considered.
14
Galvanically decoupled
15
For cable with mat. no. 524942, the shield is not connected to the cable socket.
16
Voltage-dependent resistor (VDR); breakthrough voltage 30 V @ 1 mA

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 20
Operating voltage
The SCHMIDT®Flow Sensor SS 23.700 Ex is protected against reverse
polarity of the operating voltage. It requires a DC voltage of 24 VDC with a
tolerance of ±20 % for the intended operation.
Operate the sensor only within the specified voltage range and
type of 24 VDC ± 20 %.
Undervoltage may result in malfunction; overvoltage may lead to
irreversible damage.
Specifications of the supply voltage apply to the connector of the sensor.
Voltage drops generated due to line resistances (especially “mass offset”)
must be taken into account by the customer.
The operating current of the sensor (analog signal currents included, with-
out any of the pulse outputs) is normally approx. 80 mA. With pulse out-
put
17
, the required current consumption increases to max. 200 mA
18
.
Wiring of analog outputs
Both analog outputs (flow velocity and temperature of medium) are de-
signed as high-side driver with “Auto-U/I” feature and are permanently
short-circuit protected against both rails of the operating voltage.
Nominal operation
The measuring resistance RLmust be connected between the corre-
sponding signal output and the electronic reference potential of the sen-
sor (see Figure 6-2).
Figure 6-2
17
Without signal current of the semiconductor relay
18
Both signal outputs with 22 mA (maximum measurement values); supply voltage minimal