Schmidt SS 20.415 LED User manual

SCHMIDT®Flow Sensor
SS 20.415 LED
Instructions for Use

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 LED Page 2
SCHMIDT®Flow Sensor
SS 20.415 LED
Table of Contents
1Important information.......................................................................3
2Application range.............................................................................4
3Mounting instructions.......................................................................5
4Electrical connection........................................................................7
5Signalizing .....................................................................................12
6Startup...........................................................................................15
7Information concerning operation..................................................15
8Service information........................................................................16
9Technical data ...............................................................................18
10 Declarations of conformity.............................................................19
Imprint:
Copyright 2022 SCHMIDT Technology GmbH
All rights reserved
Version: 551742.02D
Subject to modifications

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 LED 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
SS 20.415 LED 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-observanceor 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 LED Page 4
2 Application range
The SCHMIDT®Flow Sensor SS 20.415 LED (551490) is designed for
stationary use in cleanrooms under atmospheric pressure conditions and
clean environmental conditions.
The sensor measures the flow velocityof the measuring medium as stand-
ard velocity
1
wN(unit: m/s) relative to standard conditions of 1,013.25 hPa
and 20 °C. The output signal is linear and independent of pressure and
temperature of the medium. 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
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 requires laminar2flow 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 LED is designed for applications
inside closed rooms and is not suitable for outdoor use.
1
Corresponds to the real velocity under standard conditions.
2
The term “laminar” means here an air flow low in turbulence (not according to its physical
definition saying that the Reynolds number is < 2300).
!
!
!

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 LED Page 5
3 Mounting instructions
Five different mounting options are available:
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.
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). The cable plug should project from the mounting
bush by about 5 cm. 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 canstill be aligned accurately byhand,
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 cap.
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 a vertical downdraft flow from 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 (hold sensor, if necessary).

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 LED Page 6
Mounting at a wall
The straight sensor has been designed for installation at a wall.
After screwing the sensor into the sleeve, its tip must be aligned in main
direction of the gas flow which means the arrow engraved on the surface
of the housing must show approximately in the direction of positive flow.
For fine adjustment align the housing line visible on the front of the sensor
tip 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; the dashed line on the sensor tube is then
exactly on the topside of the tube).
The angular deviation should not be greater than 5° referenced
to the ideal direction of the gaseous flow. Otherwise measure-
ment accuracy may be affected (deviation > 1 %).
After finishing adjustment tighten the assembly screw using the fork
wrench until the sensor is secured against twisting.
!

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 LED Page 7
4 Electrical connection
Plug-in connector
The SCHMIDT®Flow Sensor SS 20.415 LED is equipped with a plug-in
connector 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)
Model: Binder, series 712
View on plug-in connector of sensor
Figure 4-1
Pin assignment
The pin assignment of the plug-in connector can be found in Table 1.
Pin
Designation
Function
Wire color
1
Power
Operating voltage : +UB
White
2
TXD
Do not connect3
Brown
3
RXD
Do not connect3
Green
4
OC1
Switching output 1: Direction / threshold
Yellow
5
OC2
Switching output 2: Threshold
Grey
6
Analogue
Flow velocity signal wN
Pink
7
GND
Operating voltage : Mass
Blue
Shield
Electromechanical shielding
Shield meshwork
Table 1
All signals use GND as electrical reference potential.
The wire colours mentioned in Table 1 are applicable for the use of a
SCHMIDT®cable (article nos. : 505911-4, 535279, 535281, 565072,
561972, 561973).
3
Usable with the obsolete Programming Interface (505960).

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 LED 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 housings of the
plug-in connector and the sensor which are coupled to GND (VDR
4
, in
parallel with 100 nF). The shield and / or the housing should be connected
to an anti-interference potential, e.g. ground (depending on the shielding
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 LED is protected against a po-
larity reversal of the 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 is typically 35 mA and at maximum
150 mA (including all maximal signal output currents).
4
Voltage dependent resistor; breakdown voltage 27 V @ 1 mA
!
!
!

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 LED Page 9
Analog signal output
The analog output is protected against a short circuit towards both rails.
It is available in two basic versions which differ in the representation range
(signal interval, bipolarity) additionally (see Table 2):
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: 25 mA
Maximum cable length: 10 m (recommended)
Wiring:
The voltage drop in the GND wire5of the connecting cable (mass
offset) can significantly affect the analog signal of the voltage out-
put.
5
The specific resistance of the lead of the nominal cable (0.14 mm2) is 0.138 /m (20 °C);
at L = 10 m a current of IB,max = 150 mA can cause a voltage drop up to 240 mV.
!

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 LED Page 10
Switching outputs
The SCHMIDT®Flow Sensor SS 20.415 LED is equipped with two cur-
rent limited and short-circuit proved switching outputs with following tech-
nical data:
Type: Low side driver, open collector
Maximum switching voltage US,max: 26.4 VDC
Maximum switching current IS,max: 55 mA (typ. 50 mA)
Maximum off-state resistance
6
ROff: 1.5 MΩ
Minimum load resistance RL, min: Depending on switching voltage US(see below)
Maximum load capacity CL: Depending on switching current IS(see below)
Maximum cable length: 100 m
Wiring:
Each switching output can be used as follows:
Direct driving of ohmic or inductive loads (e.g. LED or relay) with a
maximum current consumption of 50 mA.
Direct activation of digital inputs with (integrated) pull-up resistor RL
(e.g. PLC input).
Due to the internal measuring resistorwhich is connected in parallel to
the transistor, the switching stage has a comparatively low off-state re-
sistance of 1.5 M. This should be taken into account in case of a (high
resistance) pull-up resistor RL. For a digital evaluation, it is recommended
to choose a value of RL< 167 kso as to achieve an active high level
(locked transistor) which is 10 % below switching voltage USor higher.
Because of its open collector design, the switching voltage USis independ-
ent of the operating voltage UBof the sensor. Thereby it does not behave
like an ideal switch (in particular in combination with the protective mech-
anism) but exhibits in conductive condition a drop voltage UOC with follow-
ing behaviour:
Well below the maximum current IS,max, the open circuit voltage UOC
results from voltage drop via the emitter resistance REplus saturation
voltage over the collector emitter path of the switching transistor:
    
6
Measuring resistor and switching transistor; additional leakage current of the TVS diode
connected in parallel (UOC ≈ US,max): < 100 µA

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 LED Page 11
If the maximum current IS,max of 50 mA is almost reached, the emitter
resistance locks the switching transistor by an inverse feedback so that
the voltage drop over the transistor (increasing from UOC ≈ 2.6 V) rises
significantly while the current remains constant (analog current limit-
ing). From this borderline case, the minimum allowed (static) load re-
sistance RL,min at an defined voltage UScan be calculated
7
:
 

Example:
RL,min = 476 at maximum switching voltage US,max = 26.4 V.
If the load resistance is too low (e.g. short-circuit), a digital short-circuit
protection will become active which clocks the output (switch through
impulse of approx. 1 ms duration, 300 ms switched off) then on again
(transistor is conductive). This procedure is carried out until the cause
of the faulty switching is removed.
In case of a high capacitive load CL, the inrush current impulse
may trigger the quick-reacting short-circuit protection (perma-
nently) although the static current requirement is below the
maximum current IS,max. An additional resistor connected in se-
ries to CLcan eliminate the problem.
Each switching output is protected against voltage peaks by an unipo-
lar TVS diode
8
(see wiring diagram). Positive voltage impulses (e.g.
due to an inductive load) are limited to approx. 30 V, negative impulses
are short-circuited against GND (conducting-state voltage of a diode).
7
Basic current of the switching transistor can be neglected.
8
Transient Voltage Suppressor diode

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 LED Page 12
5 Signalizing
Analog output
The following is valid for all output versions of the SCHMIDT®Flow Sen-
sor SS 20.415 LED:
Representation of measuring range:
The measuring range of the flow velocity (0 … wN,max or ±wN,max) is
mapped in a linear way to the signaling range of the used analog output
type (see Table 2).
Voltage interface (U)
Current interface (I)

  

  󰇛  󰇜
Table 2
Overflow:
Flow speeds exceeding the measuring range are furthermore output in
a linear way up to 110 % of this 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.
Indication of flow direction
9
:
Depending on its type, the sensor measures flow only in one (unidirec-
tional) or in both directions (bidirectional).
In an unidirectional version (see Figure 5-1), the switching output OC1
(factory setting)
10
is used to signalize explicit a zero flow. The output
transistor locks if the flow is higher than 0 m/s and conducts if it is lower
or equal to 0 m/s.
9
Related to nominal measuring direction (defined as positive) of the sensor head.
10
OC1 can be configured optionally to any threshold value within measuring range.

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 LED Page 13
Figure 5-1
To distinguish between positive and negative flow direction, bidirec-
tional versions use either switching output OC1 (see Figure 5-2) or the
representation area of the analogue signal output is halved, that means
zero flow is defined at 50 % of signalling range (see Figure 5-3).
Figure 5-2 Figure 5-3
Error signaling:
The voltage version (0 … 10 V) is set to zero.
The current interface (4 … 20 mA) signalizes 2 mA.
Response time (damping of measured values):
By default the response time of flow measurement is 1 s.
Optionally it could be configured in the range of 0.01 … 10 s.

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 LED Page 14
Switching outputs
Both switching outputs are used as threshold value switches which mean
they change their switching condition during normal measuring operation
as soon as the measured flow velocity exceeds or falls below the adjusted
value.
Switching hysteresis:
The threshold value is symmetrically superimposed by a fixed hystere-
sis. The hysteresis width is 5 % of the threshold value (but at least
0.05 m/s) and is not configurable.
Switching polarity:
The switching polarity is defined as the change in direction of the
switching state during a certain procedure (from "locked" to "conduc-
tive" or vice versa).
Both switching outputs are configured by factory with positive polarity,
which means that a previously conducting transistor locks if switching
threshold is exceeded (and, in connection with the switching load,
switches to a positive voltage level of US).
Switching polarity is configurable by ordering.
Configuration OC1:
If the analogue indication area of the bidirectional version corresponds
to the absolute value of the measuring range, OC 1 is used to signalize
the direction (see Figure 5-2).
Otherwise it is used as an optionally programmable threshold switch
that is set to a threshold value of 0 m/s by factory.
Configuration OC2:
OC2 can generally be used as a freely programmable threshold switch
(ordering). By default the middle of the positive measuring range is
considered as the threshold value.
Error signaling:
Both switching outputs are conducting independent of their configured
switching polarity

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 LED Page 15
LED light ring
The SCHMIDT®Flow Sensor SS 20.415 LED indicates its current oper-
ating state via a light ring in the holder using coloured light code:
Colour signal
Function / failure
None
Supply voltage: None / reversed / too low
Green pulsing (2 Hz)
Supply voltage: Too high
Red pulsing (2 Hz)
Sensor defective
Red blazing
Only with current interface: Load too big (> 350 )
Green blazing
Sensor operational
Orange flashing (2 Hz)
LF-Status indicator (option)
Table 3
The function “LF-Status indicator” signals a drop out of the admissible flow
velocity range of 0.45 m/s ± 20 % (wN< 0.36 m/s or wN> 0.54 m/s).
6 Startup
The SCHMIDT®Flow Sensor SS 20.415 LED is ready within 5 seconds
after switch-on. If the sensor has a temperature different from that of the
place of use, this time will increase until the sensor has reached ambient
temperature.
7 Information concerning operation
Sterilization
The SCHMIDT®Flow Sensor SS 20.415 LED can be sterilized during
operation.
Approved disinfectants are alcohol (drying without leaving residues) and
hydrogen peroxide. If too much cleaning agent is applied to the sensor,
the "soiling detection" can be activated and the analog signal is set to error
state (0 V or 2 mA). As soon as the sensor element is dried, the sensor is
automatically reset to its normal function.
Due to its capillarity, the chamber head gap in the sensor tip can
be filled with cleaning agent. 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
compressed air blast or similar methods.
!

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 LED Page 16
Cleaning of the system
If it is necessary to clean the system in which the sensor is included using
another cleaning agent than mentioned above, the sensor tip must bepro-
tected against the penetration of inappropriate cleaning agents by means
of the protective cap included in the delivery. This is especially applicable
for cleaning agents which do not dry without leaving residues or cleaning
processes during which dirt may come into the sensor tip.
Prior to carry out problematic cleaning measures (e.g. using inad-
missible cleaning agents), the (yellow) protective cap included in
the delivery must be placed on the sensor head to protect its sen-
sor element.
See also chapter 8Service information, subchapter Cleaning of sensor
head.
8 Service information
Maintenance
A soiled sensor tip may distort the measured value. Therefore the sensor
tip must be checked for soiling at regular intervals. If it is soiled or wetted
by a liquid, the sensor sends an error signal via the analog output (0 V or
2 mA). 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
If the sensor tip is soiled or dusty, it must be carefully cleaned by means
of compressed air (avoid strong pressure impulses!). If this procedure is
not successful, the sensor tip can be cleaned by immersing and washing
it in alcohol which dries without leaving residues (e.g. isopropyl alcohol).
As soon as the alcohol has been evaporated, the sensor is again ready
for operation.
Do not shake or tap the wet sensor!
Do not try to clean the sensor tip by any type of mechanical
methods. Do not touch the sensor element located in the
chamber head. This may irreversibly damage the sensor.
Do not use strong cleaners, brush or other objects, fluffy cloths
etc. to clean the sensor tip!
Inappropriate cleaning agents may leave residues on the sen-
sor element and therefore lead to faulty measurements or re-
sult in permanent damage to the sensor element.
!
!

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 LED Page 17
If the chamber head gap of the sensor tip is completely filled
with cleaning agent, accelerate drying process by blowing it
out, if necessary.
Transport / dispatch of the sensor
Before transport or dispatch of the sensor, the delivered protec-
tive cap must be put over the sensor head. Avoid soiling or me-
chanical stress.
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 LED Page 18
9 Technical data
Measuring quantity
Normal velocity wNof air based on normal conditions
20 °C and 1013.25 hPa
Medium to be measured
Clean air or nitrogen; more gases on request
Measuring range
(±) 0 ... 1 / 2.5 / 5 / 10 m/s
Unidirectional or bi-directional
Lower detection limit
(±) 0.05 m/s
Measuring accuracy11
- Standard
- High precision
±(3 % of measured value + 0.05 m/s)
±(1 % of measured value + 0.04 m/s)
Repeatability
±1.5 % of measured value
Response time (t90)
1 s (configurable: 0.01 ... 10 s)
Storage temperature
-20 ... +85 °C
Operating temperature
0 ... +60 °C
Humidity range
Not condensing (< 95 % rel. humidity)
Operating pressure
Atmospheric (700 ... 1,300 hPa)
Operating voltage
24 VDC ± 10 %
Current consumption
Typical < 35 mA (max. 150 mA12)
Analog output
- Current
- Voltage
Short circuit protected (type by ordering)
4 ... 20 mA (RL≤ 300 Ω; CL≤ 100 nF)
0 ... 10 V (RL≥ 10 kΩ; CL≤ 10 nF)
Switching outputs
2 pc., open-collector, current-limited, short-circuit-protected
Switch 1 (OC1): Direction or threshold
Switch 2 (OC2): Threshold
Max. Load: 26.4 V DC / 55 mA
Threshold: 0 ... 100 % of end value; min. ±0.05 m/s
Hysteresis: 5 % of switching threshold; min. 0.05 m/s
Configuration: Polarity, threshold value (by ordering)
Electrical connection
Plug (male), M9, screw, 7-pin (shielded)
Line length (max.)
Voltage output: 10 m / current output: 100 m
Protection type13
IP65
Protection class
III (SELV) or PELV (EN 50178)
Mounting position
Arbitrary postioning of bracket
Dimensions / material:
- Sensor head
- Sensor tube:
Straight (L)
Angled (H x L)
- Screw nut
Ø 9 mm x 10 mm Stainless steel 1.4404
Ø 9 mm Stainless steel 1.4404
300 / 301 …1,000 mm
150 / 270 mm x 300 mm
Stainless steel 1.4404
11
Under reference condition
12
Including all signal output currents
13
Only with correctly attached connecting cable

Instructions for Use - SCHMIDT®Flow Sensor SS 20.415 LED Page 19
10 Declarations of conformity
SCHMIDT Technology GmbH herewith declares in its sole
responsibility, that the product
SCHMIDTFlow Sensor SS 20.415 LED
Part-No. 551 490
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 LED Page 20
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