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