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:

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

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.

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

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

to flow direction should not exceed ±5° in order to

avoid significant measuring errors (> 1 %).

Commercially available welding stud (not included in delivery) must be welded.

Countersunk head, not included in the delivery.

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

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

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.

= Length of whole measuring distance

= Length of run-in distance

= Length of run-out distance

= 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

Here the term “laminar” means an air flow low in turbulence (not according to its physical

definition saying that the Reynolds number is < 2300).

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







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

Inner diameter of pipe [m]

Cross section area of tube [m2]

Flow velocity in the middle of tube [m/s]

Average flow velocity in tube [m/s]

Profile factor (for tubes with a circular cross section A)



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.

Designation

Function

Wire colour

Power

Operating voltage : +UB

White

TXD

Do not connect8

Brown

RXD

Do not connect8

Green

OC1

Switching output 1: Direction or threshold

Yellow

OC2

Switching output 2: Threshold

Grey

Analogue

Velocity signal wN

Pink

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).

Usable with the obsolete Programming Interface (505960).

View on connector of sensor

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