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Product Detail
Paramagnetic oxygen Sensor SPM-O2 Module II
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Paramagnetic oxygen Sensor SPM-O2 Module II
Type: SPM-O2 Module II
Measurement Gas: Oxygen
Accuracy: 1% FS
Response time: ~3s
Warm-up time: 30min
Resolution: 1.0E-4
Linearity error: 1% FS
Input Temp.: 5 - 35℃
Input flow: (0.2-1)L/min(Flow change≤0.02L/min)
Output signal: 4-20mA
Work Temp.: -5℃~50℃
Storage Temp.: -20℃~60℃
Humidity: 0% RH~90% RH
Power: 24 VDC
Dimension: 162mm*106mm*110mm(withpackage)

The paramagnetic sensor utilizes the paramagnetic susceptibility of oxygen.

The sensor incorporates two glass spheres mounted on a rotating suspension. This assembly is suspended in a strong magnetic field. The oxygen in the surrounding gas is attracted to the magnetic field, resulting in a force on the lass spheres. The strength of torque acting on the suspension is proportional to the oxygen content of the surrounding gases.

Refer to the Figure, the measuring system  isnull-balance. First thezeroposition of the suspension assembly, as measured in nitrogen, is sensed by a phot0-sensor that receives light reflected from a mirror attached to the suspension assembly. The feedback achieves two objectives.

First, when oxygen is introduced to the cell, the torque acting upon the suspension assembly is balanced by a restoring torque due to the feedback current in the coil. The feedback current is directly proportional to the volume magnetic susceptibility of the sample gas and hence, after calibration, to the partial pressure of oxygen in the sample. Therefore the current gives an accurate measurement of the concentration ofoxygen in the gas mixture.

Second, the electromagnetic feedback stiffenthe suspension, damping it heavily and increasing its natural frequency, making the suspension resilient to shock.

As the instrument uses an absolute measurement principle, once built and factory calibrated, it does not require any further factory calibration.


Product Name




Measuring range:


Warm up time:


Response time:

about 3s

Detection Limit (3sigma)

1 %  O2


1% of O2

Stability (zero)   :

<0.2 % of  O2  per week

Stability (span)  :  


Temperature Drift. (zero):

<0,06 % of O2 per °C

Flow rate influence

<0.1% of O2

Effect of oblique

<0.02% of O2 per 1°

Effect of humidity vol.% O2 at N2:

<0.5% at 20°C

Analog Output :

4 20 mA

Power Supply:


Power  Inlet

Weipu SP1310/S7I

Inlet Gas requirement:

Gas Inlet Flow

(0.2-1)L/min(Flow fluctuations0.02L/min)

Inlet Gas pressure:  

Min 0.01bar, Max 1bar

Inlet  Gas Temp.


Moisture in Gas

not condensing

inlet gas dew point5±0.1

Dust in gas flow

100µg/m³, ≤1µm

Calibration Reference Gases Requirement:

Zero calibration gas

99.999% N2

Span calibration gas

85% FS~110% FS


For O2 channel, could use dry and clean air to make span calibration if the measuring range is (0…25)%.

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