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EW0826A2_en - rev. A 

Oxygen detectors 

 URS20SI 

05/10/2020 

Gas detection systems for industrial environments 

2/8

 

 

Technical 
characteristics 

 

Type of sensor 

Electrochemical cell 

Detectable Gas 

O

excess 

O

2

 deficiency 

Power supply 

11÷28Vdc 

Max power consumption 

2.5W 

Measuring range  

0…30% O

2

 

Precision 

 2,5% of full scale range (in air) 

Repeatability 

 2,5% of full scale range 

Measurement resolution 

0.1% O

2

 

Microprocessor resolution 

1024 points (10 bit) 

Digital filter system 

Kalman Filter 

Watchdog 

Internal 

Warm-up time 

< 2m 

Stabilization time 

< 2m 

Response time 

< 10s (T20), < 45s (T90) 

Average Sensor life (in air) 

120 weeks 

Sensor type settings 
(O

2

 excess or deficiency) 

S1.7 DIP switch 

OFF (O

2

 excess) 

S1.7 DIP switch 

ON (O

2

 deficiency) 

Threshold limit settings  
(S1.8 = OFF, default): 

Pre-alarm 

1

st

 threshold alarm 

2

nd

 threshold alarm 

 
 

23% O

2

 

25% O

2

 

27% O

2

 

 
 

19% O

2

 

17% O

2

 

15% O

2

 

Threshold limit settings  
(S1.8 = ON): 

Pre-alarm 

1

st

 threshold alarm 

2

nd

 threshold alarm 

 
 

22% O

2

 

23% O

2

 

24% O

2

 

 
 

20% O

2

 

19% O

2

 

18% O

2

 

4..20mA Output 

Proportional mode 
(default) 

 

Consumption mode 
(applications at 1 or 2 
thresholds) 
4…20mA Output reference 
selection: 

 
-   4mA   =   0% O

2

 

- 20mA   = 30% O

2

 

 
-   0mA   = no alarm 
- 10mA   = 1

st

  threshold alarm 

- 20mA   = 2

nd

  threshold alarm 

 
by jumper selectable polarity 

4…20mA output load resistor 

- up to 200

 at 12Vdc power supply 

- 200

 

 700

 at 24Vdc power supply 

Operating Temperature 
Storage Temperature

 

-20 

 50 °C 

-20 

 70 °C

 

Relative Humidity 

(without condensing) 

-

 

Operation 

-

 

Storage

 

 

15 

 90 %RH 

45 

 75 %RH

 

Operating pressure (KPa) 

80 

 110 

Air speed (m/s) 

 6 

Visual warnings 

Red LED visible with detector energised 

Dimensions and weight 

See dedicated section 

Options & Accessories 

 

Card with 4 SPDT relays 

UZR20.4

 

NO or NC contacts available, jumper 
selectable 

See threshold limit settings 

Maximum relay capacity: 

50mA at 24Vac/dc, 100mA at 12Vac/dc 

Relay operating mode: 

-

 

direct: relay ON when an event is 
detected 

-

 

reverse: relay ON when no event is 
detected 

TUL40..

 Gas calibration kit 

See installation and commissioning chapter 

TUS40   

Handheld terminal   

for service and maintenance  

See installation and commissioning chapter 

CRG40

   Gas collecting cone 

See dedicated data sheet 

PAP40

   Powerful jets protection 

See dedicated data sheet 

 
EC Conformity 
EMC Directives / Standards 
 
LVD Directives / Standards 

 
 

Electromagnetic Compatibility Directive 
2014/30/EU / EN50270 / EN 61326-1 
Not applicable 

Summary of Contents for EsiWelma Sensigas URS20SI

Page 1: ...ore in general where oxygen is stored Oxygen deficiency is an indirect measurement of the presence of other explosive or asphyxiant gases that deplete the oxygen in the air URS20SI sensors can be used...

Page 2: ...esholds 4 20mA Output reference selection 4mA 0 O2 20mA 30 O2 0mA no alarm 10mA 1st threshold alarm 20mA 2nd threshold alarm by jumper selectable polarity 4 20mA output load resistor up to 200 at 12Vd...

Page 3: ...nstructions for location of the detectors The detectors must be installed 1 where accidental gas leakages are possible 2 at least 1 5m away from heat sources or from vent holes 3 not in spaces where v...

Page 4: ...or are shown in the Technical Specifications chapter In order to change the default settings switch off the power supply input the new settings at the JP2 jumper circuit or at the S1 DIP switch as sho...

Page 5: ...ep 1 Insert the connection slot provided with the relay card into the control card making sure the flexible tab is towards the main terminal board Find CN3 connector CN3 connector Connection slot flex...

Page 6: ...nstallation The sensors are factory calibrated so they normally do not require any other calibration once installed Still after installation an operational check of the sensors is recommended The dete...

Page 7: ...return the sensor concerned to the supplier installer who in turn will send it back to the manufacturer Sensors may need to be re calibrated using the TUL40 calibration kit and the TUS40 20 handheld t...

Page 8: ...in by Installer Installer s stamp and signature Installation site Product order number Part Number Manufacturing date Installation date Replacement date Routine checks To be filled in by Installer Se...

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