Schmidt SS 20.400 User manual

SCHMIDT®Flow Sensor
SS 20.400
Instructions for Use

Instructions for Use –SCHMIDT®Flow Sensor SS 20.400 Page 2
SCHMIDT®Flow Sensor SS 20.400
Table of Contents
1Important Information ......................................................................3
2Application Range ...........................................................................4
3Mounting Instructions ......................................................................5
4Electrical Connection.....................................................................10
5Signalizing .....................................................................................15
6Startup...........................................................................................18
7Information on Continuous Operation ...........................................18
8Service Information........................................................................19
9Technical Data...............................................................................22
10 Declarations of Conformity............................................................23
Imprint:
Copyright 2021 SCHMIDT Technology GmbH
All rights reserved
Revision: 504301.02G
Errors and technical modifications subject to change

Instructions for Use –SCHMIDT®Flow Sensor SS 20.400 Page 3
1 Important Information
These instructions for use contain all required information for a fast com-
missioning and a safe operation of SCHMIDT®Flow sensors of the
SS20.400 type.
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 instruc-
tions for use - will forfeit any warranty and exclude any liability.
The unit is designed exclusively for the use described below (see chap-
ter 2). In particular, it is not designed for direct or indirect protection of
personal and machinery.
SCHMIDT Technology cannot give any warranty as to its suitability for
certain purpose and cannot be held liable for errors contained in these
instructions for use or for accidental or sequential damage in connec-
tion with the delivery, performance or use of this unit.
Symbols used in this manual
In the following section, all the symbols used in this manual are explained.
Danger warnings and safety instructions - read carefully!
The non-observance of these instructions may lead to personal
injury or malfunction of the device.
General information
All dimensions are indicated in mm.
!

Instructions for Use –SCHMIDT®Flow Sensor SS 20.400 Page 4
2 Application Range
The SCHMIDT®Flow sensor SS 20.400 (article number: 518210) is de-
signed for stationary use in clean rooms, air ducts or air shafts under at-
mospheric pressure conditions and clean environmental conditions.
The sensor measures flow velocity of the measuring medium as standard
velocity
1
wN(unit: m/s) relative to standard pressure of 1,013.25 hPa and
standard temperature of 20 °C. The output signal is linear and independ-
ent of pressure and temperature of the medium.
Optionally the sensor is able to measure both directions (see chapter 5).
The decisive characteristics of the product are listed below:
Measuring task
oMeasurement of flow velocity
oDetection of flow direction (bidirectional version)
Application examples
oLaminar-flow monitoring in cleanrooms
oMonitoring of room cross-flow
oCooling air monitoring
oFlow measurement in test benches
Only suitable for use in clean gases.
In particular, the medium to be measured must not contain oils,
residue forming substances or abrasive particles.
When transporting the sensor or when carrying out not approved
cleaning measures, always place the protective cap on the sen-
sor.
The SCHMIDT®Flow sensor SS 20.400 is designed for applica-
tions inside closed rooms and is not suitable for outdoor use.
1
Corresponds to the actual velocity under standard conditions.
!
!
!

Instructions for Use –SCHMIDT®Flow Sensor SS 20.400 Page 5
3 Mounting Instructions
For installation the following accessories are available:
Type / art. no.
Drawing
Assembly
Compressing
fitting
532160
G1/2
39
SW17
SW27
14 Ø9,2+0,1
- Immersion sensor
- Pipe (typ.)
- Wall
- Screwing into a clamp2
- Material:
Stainless steel 1.4571
Clamp collar PTFE
Wall mounting
flange
520181
- Immersion sensor
- Wall (plain surface)
- Attachment with:
2 screws M53
- Material:
Stainless steel 1.4404
PTFE
O-ring Viton
Wall mounting
bracket
(an. Aluminium)
503895
- Room-to-room overflow
- Wall (plain surface)
- Attachment with:
2 screws M5 x 12
- Material:
Aluminium, anodised
Wall mounting
bracket
(stainless steel)
551740
- Room-to-room overflow
- Wall (plain surface)
- Attachment with:
2 screws M5 x 12
- Material:
Stainless steel 1.4404
Table 1
All mounting fixtures fasten the sensor by means of frictional clamping on
the sensor tube. This enables stepless positioning of the sensor in the
holder both axially in direction of the longitudinal sensor axis (immersion
depth) as well as in rotational direction around the same axis (tilting).
The angle of tilt
4
to flow direction should not exceed ±5° in order to
avoid significant measuring errors (> 1 %).
2
Commercially available welding stud (not included in delivery) must be welded.
3
Countersunk head, not included in the delivery.
4
Deviation between measuring direction of sensor head and flow direction.
Clamping screw
Set screw M4x3
Stainless A4

Instructions for Use –SCHMIDT®Flow Sensor SS 20.400 Page 6
In inhomogeneous, laminar flow fields (e.g. a quasi-parabolic speed
profile in a tube), the sensor tip should be positioned at the place at
which the highest speed occurs (adjustment of the immersion depth
see Figure 3-1) since this point has normally the largest distance to
interfering elements such as boundary surfaces.
If correctly mounted, both the compression fitting and the wall mounting
flange are tight up to a gauge pressure of 500 mbar
5
.
The customer himself must ensure that the sensor is protected
against an unintentional pressing out caused by the overpres-
sure.
Tube-related flow
Installation in a flow guiding tube is carried out by means of a compression
fitting (532160, see Figure 3-1):
Screw the threaded part of the compression fitting into the pipe union
(hexagon AF 27). Unscrew the spigot nut (AF17) to such an extent that
the sensor can be inserted without jamming.
Introduce sensor into the compression fitting until its tip is located in
the middle of the tube. Then tighten the spigot nut slightly using the
fork wrench AF17 to fix the sensor.
Align sensor to nominal flow direction (direction of arrow) considering
that immersion depth must be maintained.
The angular deviation should not be greater than 5° refer-
enced to the ideal direction of the gaseous flow. Otherwise
measurement accuracy may be affected (deviation > 1 %).
Tighten spigot nut by turning the fork wrench (AF17) by a quarter while
maintaining the sensor in position.
Figure 3-1
5
The screw-in thread of the compression fitting must be sealed, e.g. with a teflon tape.
!
!
Threaded part
532160

Instructions for Use –SCHMIDT®Flow Sensor SS 20.400 Page 7
To reach the accuracy specified in its data sheets, the SS 20.400 has to
be positioned in a straight conduit and at a place with undisturbed flow
profile. An undisturbed flow profile can be achieved if a sufficiently long
distance in front of the sensor (run-in distance) and behind the sensor
(run-out distance) is held absolutely straight and without disturbances
(such as edges, seams, bends, etc.).
Correct measurements require laminar6flow with as low turbu-
lence as possible.
The design of the run-out distance is also important, since disturbances
do not only act in direction of the air flow but also lead to turbulences
opposite to flow direction.
L
= Length of whole measuring distance
L1
= Length of run-in distance
L2
= Length of run-out distance
D
= Inner diameter of measuring distance
Figure 3-2
The following Table 2 shows the required straight conduit lengths depend-
ing on tube diameter and different disturbances.
This table lists the minimum values required in each case. If the listed
straight conduit lengths cannot be achieved, measurement accuracy may
be impaired or additional actions are required like the use of flow rectifi-
ers
7
.
6
Here the term “laminar” means an air flow low in turbulence (not according to its physical
definition saying that the Reynolds number is < 2300).
7
E. g. honeycombs made of plastics or ceramics; profile factor may change therefore.
!

Instructions for Use –SCHMIDT®Flow Sensor SS 20.400 Page 8
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 2
When mounting the sensor in a tube with a known cross section area, the
output signal of the flow velocity can be used to calculate the standard
volumetric flow of the medium:
AwV
wPFw
DA
NN
NN




2
4

SCHMIDT Technology provides on its homepage a convenient calcula-
tion tool to compute flow velocity or volume flow in pipes (circular or rec-
tangle) for all its sensor types and measuring ranges:
www.schmidt-sensors.com or www.schmidttechnology.de
D
Inner diameter of pipe [m]
A
Cross section area of tube [m2]
N
w
Flow velocity in the middle of tube [m/s]
N
w
Average flow velocity in tube [m/s]
PF
Profile factor (for tubes with a circular cross section A)
N
V

Standard volumetric flow [m3/s]

Instructions for Use –SCHMIDT®Flow Sensor SS 20.400 Page 9
Wall mounting
The wall mounting flange (520181) is designed for installation of the sen-
sor SS 20.400 as an immersion sensor through a wall (e.g. wall of a flow
box). The threaded bush included in the delivery has a base provided with
a plane contact surface and two holes which allow a fast and easy instal-
lation by means of two screws.
All advantages, requirements and installation instructions regarding the
stepless sensor installation are applicable for the compression fitting (see
subchapter: Tube-related flow).
Mounting for measuring room-to-room overflow
A room-to-room overflow sensor is fixed by means of a wall mounting
bracket (503895 made of anodized aluminium or 551740 made of stain-
less steel). The sensor should be placed in flow direction behind the wall
opening, whereas the sensor tip must be located in the middle of the open-
ing (see Figure 3-3 for exemplary use of 503895).
Figure 3-3
The application of a SS 20.400 with bidirectional measurement
capability allows the detection of backflow and is therefore able
to signalize critical operating conditions.
!
Wall opening
Setscrew M5
For fixation of sensor
Cylinder screw M5
Internal hexagon (2x)
Flow

Instructions for Use –SCHMIDT®Flow Sensor SS 20.400 Page 10
4 Electrical Connection
Plug-in connector
The Flow Sensor SS 20.400 is equipped with a plug-in connector which
is firmly integrated in the housing. The connector has the following data:
Number of connection pins: 7 (plus shield connection on the metallic housing)
Type: Male
Fixation of connecting cable: Screw M9 (on cable)
Protection type: IP67 (with properly attached cable)
Model: Binder, series 712
Pin numbering:
Figure 4-1
The pin assignment of the plug-in connector can be found in Table 3.
Pin
Designation
Function
Wire colour
1
Power
Operating voltage : +UB
White
2
TXD
Do not connect8
Brown
3
RXD
Do not connect8
Green
4
OC1
Switching output 1: Direction or threshold
Yellow
5
OC2
Switching output 2: Threshold
Grey
6
Analogue
Velocity signal wN
Pink
7
GND
Operating voltage : Mass
Blue
Shield
Electromechanical shielding
Shield meshwork
Table 3
All signals use GND as electric reference potential.
The wire colours mentioned in Table 3 are applicable for the use of a
SCHMIDT®cable (article no.: 505911-4, 535279 and 535281).
8
Usable with the obsolete Programming Interface (505960).
View on connector of sensor