Schmidt SS 20.415 Twin User manual

SCHMIDT®Flow Sensor
SS 20.415 Twin
Instructions for Use

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 Twin Page 2
SCHMIDT®Flow Sensor
SS 20.415 Twin
Table of Contents
1Important information.......................................................................3
2Application range.............................................................................4
3Mounting instructions.......................................................................5
4Electrical connection........................................................................7
5Signalizing .....................................................................................10
6Startup...........................................................................................11
7Information concerning operation..................................................11
8Service information........................................................................12
9Technical data ...............................................................................14
10 Declarations of conformity.............................................................15
Imprint:
Copyright 2022 SCHMIDT Technology GmbH
All rights reserved
Version: 568106.02
Subject to modifications

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 Twin 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 model
SS 20.415 Twin.
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
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 - please read them!
Non-observance of these instructions may lead to personal injury
or malfunction of the device.
General note
All dimensions are given in mm.
!

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 Twin Page 4
2 Application range
The SCHMIDT®Flow Sensor SS 20.415 Twin (566950) is designed for
stationary use in cleanrooms under atmospheric pressure conditions and
clean environmental conditions.
The sensor consists of two independent, spatially closely
1
positioned sen-
sor heads. Both of them are measuring the flow velocity of the measured
medium as standard velocity
2
wN(unit: m/s) relative to standard conditions
of 1,013.25 hPa and 20 °C. The respective output signals are linear and
independent of pressure and temperature of the medium. The decisive
characteristics of the product are listed below:
Measuring task
oRedundant measurement of flow velocity at one spot of the laminar
flow field.
oOutput of the measured values via two independent analog signals.
Application examples
oSimultaneous control and monitoring of laminar flow in cleanrooms.
Special operating notes
Only suitable for the use in clean gases.
The medium to be measured must not contain oils, residue form-
ing substances or abrasive particles.
Correct measurements require a laminar3flow with as low turbu-
lence as possible.
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 20.415 Twin is designed for
applications inside closed rooms and is not suitable for outdoor
use.
Note:
The positions "A" respective "B" are assigned to both probes (see Figure
1) in order to be able to clearly assign their output signals (wNA resp. wNB;
see also Figure 2 and Table 2).
1
Aerodynamic cross influences are eliminated by the common adjustment.
2
Corresponds to the real velocity under standard conditions.
3
The term “laminar” means here an air flow low in turbulence (not according to its physical
definition saying that the Reynolds number is < 2300).
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!
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Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 Twin Page 5
3 Mounting instructions
The following five mounting options are available for installtion:
Type 1
For mounting in
ceilings or frames
with wall thickness
from 1 … 22 mm.
Opening Ø 26 mm
necessary (mount-
ing with counter
nut) or a thread
M25 x 1.5 in ceiling
frame.
Type 2
For mounting in
ceiling frames with
existing opening
with PG21 winding
(e.g. sprinkler
opening in ceiling
frames).
Type 3
For mounting in
ceiling frames with
thickness of 21 …
40 mm, especially
for ceiling frames
out of hollow pro-
files.
Openings required
with Ø 26 mm and
Ø 28.5 mm.
Type 4
For welding in
stainless steel
ceilings.
Type 5
For mounting under
a ceiling or at a wall
with two screws M6.
Opening of Ø 15 mm
for cable necessary
and 2 threads M6.
Pressure-tight up to
300 mbar.
Table 1
Mounting sequence
If not yet in place, first drill a bore into the wall or ceiling for installing the
mounting bush. Then the mounting bush is fastened in the wall or ceiling.
Feed connecting cable from cleanroom side through the mounting bush
(open cable ends at first) until the cable jack protrudes by about 5 cm out
of the receptable. There must be enough room behind the mounting bush,
to allow the cable to be pushed backward when screwing in the sensor.
Then connect sensor with connection cable (plug in cable connector and
screw on sleeve nut), insert sensor into mounting bush and tighten mount-
ing screw by hand. Now the sensor can still be aligned accurately by hand,
if required. Finally, the holding fixture screw must be tightened with a key
wrench (wrench size 22) until the sensor is sufficiently secured against
twisting (hold sensor, if necessary).
Prior to commissioning the sensor, remove the protective caps.

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 Twin Page 6
Mounting beneath a ceiling
The angled sensor has been designed for mounting beneath a ceiling.
After screwing the sensor into the ceiling sleeve, its tip is automatically in
the correct position to measure the vertical downdraft flow beneath the
filter outlet. Only the torsional angle of the sensor arm (parallel to ceiling)
has to be aligned. Then tighten the assembly screw using the key wrench
until the sensor is secured against twisting (SW22; hold sensor, if neces-
sary).
Mounting at a wall
The straight sensor has been designed for installation at a wall.
After screwing the sensor into the receptable (tighten by hand), aligned it
as follows:
First, the sensor must be positioned in the flow field so that its measuring
direction corresponds to the flow direction. For this, the arrow engraved
on the housing’s surface (see Figure 1) must point approximately in the
direction of the air flow. For finer adjustment align the housing line visible
on the front of the sensor tip in parallel to the flow direction as precisely
as possible (e.g. in case of a vertical downdraft the sensor arrow has to
point downward to the floor and the housing line is also vertically).
Figure 1
The angular deviation should not be greater than 3° referenced
to the ideal direction of the gaseous flow. Otherwise measure-
ment accuracy may be affected (deviation > 1 %).
Finally, fully fasten the assembly screw using the fork wrench (SW22; hold
sensor, if necessary) to prevent the sensor from unintentional rotating.
!

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 Twin Page 7
4 Electrical connection
Plug-in connector
The SCHMIDT®Flow Sensor SS 20.415 Twin is equipped with a plug-in
connector which is firmly integrated in the probe. The connector has the
following data:
Number of connection pins: 7 (plus shield connection on the metallic enclosure)
Type: Male
Fixation of connecting cable: Screw M9 (on cable)
Model: Binder, series 712
Pin numbering:
View on plug-in connector of sensor
Figure 2
Pin assignment
The pin assignment of the plug-in connector can be found in Table 2.
Pin
Designation
Function
Wire color
1
Power
Operating voltage : +UB
White
2
RS485 A
Do not connect4
Brown
3
RS485 B
Do not connect
Green
4
Aout Flow B
Probe B: Velocity signal wNB
Yellow
5
RS_Select
Do not connect
Grey
6
Aout Flow A
Probe A: Velocity signal wNA
Pink
7
GND
Operating voltage : Mass
Blue
Shield
Electromechanical shielding
Shield meshwork
Table 2
All signals use GND as electrical reference potential.
The wire colours mentioned in Table 2 are applicable for the use of a cable
delivered by SCHMIDT®(article numbers: 505911-4, 535279, 535281,
561972, 561973, 565072).
4
Manufacturer use only - risk of destruction in case of incorrect connection

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 Twin Page 8
Electrical assembly
During electrical installation ensure that no voltage is applied and
inadvertent activation is not possible.
The cable shield is electrically connected to the metallic enclosure of the
plug-in connector and the sensor which are coupled to GND (VDR
5
, in
parallel with 100 nF). The shield and / or the enclosure should be con-
nected to an anti-interference potential, e.g. ground (depending on shield-
ing concept).
The appropriate protection class III (SELV) respective PELV (ac-
cording to EN 50178) has to be considered.
Operating voltage
The SCHMIDT®Flow Sensor SS 20.415 Twin is protected against a po-
larity reversal of its operating voltage.
It has a nominal operating voltage range of UB= 24 VDC ± 10 %.
Only operate sensor within the defined operating voltage range
(21.6 ... 26.4 VDC).
Undervoltage may result in malfunction, overvoltage may lead to
irreversible damage to the sensor.
The specifications for the operating voltage are valid for the connection at
the sensor. Voltage drops generated due to line resistances must be con-
sidered by the customer.
Current consumption of the sensor (incl. both signal outputs) in the con-
figuration with voltage outputs is typically
6
26 mA and at maximum 32 mA.
With current interfaces the sensor requires typically 30 mA and at maxi-
mum 45 mA.
5
Voltage dependent resistor; breakdown voltage 27 V @ 1 mA
6
Typical: wN= 0.45 m/s and UB= UB,Nenn ; maximum: wN= overflow and UB= UB,min
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Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 Twin Page 9
Analog signal outputs
The signal characteristic as current or voltage interface is defined on or-
dering and applies to both analog outputs commonly (see Table 3):
Current interface:
Signal range: 4 ... 20 mA
Type: High side driver, load resistance against GND
Maximum load resistance RL: 300 Ω
Maximum load capacity CL: 100 nF
Maximum cable length: 100 m
Wiring:
Voltage output:
Signal range: 0 ... 10 V
Type: High side driver, load resistance against GND
Minimum load resistance RL: 10 kΩ
Maximum load capacity CL: 10 nF
Maximum short-circuit current: 35 mA (current limited)
Maximum cable length: 10 m (recommended)
Wiring:
The voltage drop in the GND wire7of the connecting cable (mass
offset) may cause a significant distortion of the analog voltage
output signal.
7
The specific resistance of a lead of the nominal cable (0.14 mm2) is 0.138 /m (20 °C);
at L = 10 m a current of IB,U,max = 32 mA can cause a voltage drop up to 50 mV.
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Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 Twin Page 10
5 Signalizing
Analog outputs
The following applies to both output variants of the SS 20.415 Twin:
Representation of measuring range:
The measuring range of flow velocity (0 … wN,max) is mapped in a linear
way to the signal range of the respective interface type (see Table 3).
Voltage interface (U)
Current interface (I)

  

  󰇛  󰇜
Table 3
Overflow:
Flow speeds exceeding the measuring range are furthermore output in
a linear way up to 110 % of the measuring range (11 V or 21.6 mA), to
signalize clearly that there is an overflow.
For higher values of flow the output signal remains constant.
Error signaling:
The voltage version (0 … 10 V) is set to 0 V.
The current interface (4 … 20 mA) signalizes 2 mA.
Response time (damping of measured values):
By default the response time of flow measurement is 5 s.
LED light ring
The SS 20.415 Twin indicates its current operating state via a light ring in
its bracket:
Colour signal
Function / failure
None
Supply voltage: None / reversed / too low
Green pulsing (2 Hz)
Supply voltage: Too high
Green blazing
Sensor operational
Table 4

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 Twin Page 11
6 Startup
The SCHMIDT®Flow Sensor SS 20.415 Twin is ready within 5 seconds
after switch-on.
If the sensor has a temperature different from that of the installation site,
this time will be extended until the sensor has become acclimatized.
7 Information concerning operation
Sterilization
The SS 20.415 Twin can be sterilized during operation.
Approved disinfectants are alcohol (drying without leaving residues) and
hydrogen peroxide. On wetting a sensor element with cleaning liquid, the
"soiling detection" can be triggered, causing the associated analog signal
to enter error state (0 V or 2 mA). As soon as the sensor element is dried,
the sensor automatically returns to its normal function.
Due to its capillarity, the gap of the measurement chamber can
be filled completely with cleaning liquid. In this case, it is possible
that it will take more than one hour until the liquid is evaporated
and the sensor works again without problems. To accelerate the
drying process, the measuring gap can be cleaned by means of
a short and soft blast of compressed air or similar methods.
Cleaning of the system
If it is necessary to clean the system in which the sensor is installed by
using another cleaning agent than mentioned above, the sensor heads
must be protected by means of the supplied protective caps.
This applies in particular to cleaning agents that do not dry without leaving
residues or cleaning processes may flush into the measurement cham-
bers.
In case of problematic cleaning measures (e.g. with inadmissible
cleaning agents), the supplied yellow protective caps must be
placed on both sensor heads to protect their sensor elements.
See also chapter 8Service information, subchapter Cleaning of sensor
head.
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Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 Twin Page 12
8 Service information
Maintenance
Contaminations in the measuring chamber of a sensor head may result in
a distortion of the measured value. Therefore the sensor heads must be
checked for soiling at regular intervals.
In case of heavy contamination or wetting of any of the sensor head’s
measurement chamber, the sensor provides an error signal (0 V or 2 mA)
at the respective analog output. In this case, clean sensor as described
below.
If the error signal does not disappear after cleaning and drying, the sensor
must be sent in to the manufacturer for repair.
Cleaning of sensor head
In case of contamination or wetting of the measuring chamber of a probe
it may be carefully blown out using compressed air (avoid strong pressure
impulses!).
If this procedure is not successful, the sensor head can be cleaned by
immersing and washing it in alcohol or a similar cleaning agent, which
dries without leaving residues (e.g. isopropyl alcohol).
Do not shake or tap the wet sensor!
Do not try to clean the sensor tip by any type of mechanical
methods. Any contact with the sensor element embedded in
the measuring chamber leads to irreversible damage to it.
Do not use strong cleaners, brush or other objects, fluffy cloths
etc. to clean the sensor tip!
Inappropriate cleaning agents may be deposited on the sensor
element and therefore lead to incorrect measurements or even
damage it permanently.
If the measuring chamber of a sensor head is completely filled
with cleaning agent, accelerate the drying process by blowing
it out, if necessary.
As soon as the cleaning agent has been evaporated without residues, the
sensor is again ready for operation.
Transport / dispatch of the sensor
When transporting or dispatching the SS 20.415 Twin, the sup-
plied protective caps should be placed over the sensor’s heads.
Avoid soiling of or mechanical impacts on the sensor’s heads.
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!

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 Twin Page 13
Calibration
If the customer has made no other provisions, we recommend repeating
the calibration at a 12-month interval. To do so, the sensor must be sent
in to SCHMIDT Technology.
Spare parts or repair
No spare parts are available, since a repair is only possible at SCHMIDT
Technology. In case of defects, the sensors must be sent in to the sup-
plier for repair.
When the sensor is used in systems important for operation, we recom-
mend keeping a replacement sensor in stock.
Test certificates and material certificates
Every newly produced sensor is accompanied by a certificate of compli-
ance according to EN10204-2.1. Material certificates are not available.
Upon request, we shall prepare, at a charge, a factory calibration certifi-
cate, traceable to national standards.

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 Twin Page 14
9 Technical data
Measuring quantity
Normal velocity wNof air based on normal conditions of
20 °C and 1013.25 hPa
Medium to be measured
Clean air or nitrogen; more gases on request
Measuring range
0 ... 1 / 2.5 m/s
Lower detection limit
0.05 m/s
Measuring accuracy8
- Standard
- High precision
±(3 % of measured value + 0.05 m/s)
±(1 % of measured value + 0.04 m/s)
Response time (t90)
5 s
Storage temperature
-20 ... +85 °C
Operating temperature
0 ... +60 °C
Humidity range
Measuring mode: Non-condensing (< 95 % RH)
Operating pressure
Atmospheric (700 ... 1,300 hPa)
Operating voltage
24 VDC ± 10 %
Current consumption9
Typical 26 (32) mA; max. 32 (45) mA
Analog outputs
- Current
- Voltage
Short circuit protected (type by ordering)
2 x 4 ... 20 mA (RL≤ 300 Ω; CL≤ 100 nF)
2 x 0 ... 10 V (RL≥ 10 kΩ; CL≤ 10 nF)
Electrical connection
Plug (male), M9, screw, 7-pin (shielded)
Max. line length
100 m / voltage output: 10 m (recom.)
Protection type10
IP65
Protection class
III (SELV) or PELV (EN 50178)
Mounting position
±3° relative to flow direction (unidirectional; straigt version)
Dimensions / material:
- Sensor head
- Sensor tube:
Straight (L)
Angled (H x L)
- Bracket
- Screw nut
- Light ring
Ø 9 mm x 10 mm Stainless steel 1.4404
Ø 9 mm Stainless steel 1.4404
300 mm
150 / 270 mm x 300 mm
Ø 18 mm x 17,7 mm Stainless steel 1.4404
Ø 25 mm (SW22) Edelstahl 1.4404
Ø 14 mm PC
Table 5
8
Under reference condition
9
Values in brackets apply to the variant with current interfaces
10
Only with correctly attached connecting cable

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 Twin Page 15
10 Declarations of conformity
SCHMIDT Technology GmbH herewith declares in its sole
responsibility, that the product
SCHMIDTFlow Sensor SS 20.415 Twin
Part-No. 566 950
is in compliance with the appropriate
European guidelines and standards
and
UK statutory requirements and designated
standards.
The corresponding declarations of conformity can be down-
load from SCHMIDT®homepage:
www.schmidt-sensors.com
www.schmidttechnology.de

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 Twin Page 16
SCHMIDT Technology GmbH
Feldbergstraße 1
78112 St. Georgen
Germany
Phone [phone] / 899-0
Fax [phone] / 899-101
Email [e-mail]
URL www.schmidt-sensors.com
www.schmidttechnology.de