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We are a proud member of


German Biogas Association

EngineSens Motorsensor GmbH

Mannheimer Str. 44 b

E-Mail  info@enginesens.com

D-68519 Viernheim / Germany

phone  +49 6204-986 08 23

fax       +49 6204-986 08 25

Sensing the future

Our Portfolio:

Temperature Probes, Differential Pressure Sensors for Particle Filters, Airflowmeters, NOx-Probes and consultancy regarding Exhaust Gas Purification and Exhaust Gas Sensors.




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NOx 0-1500 ppm 24 V small

NOx-Probe  24 V 1500 ppm

part-no. 70501

Our NOx-sensor is a reliable heavy-duty version of common components used in passenger cars. As it is a heavy duty version the life-time expectance is much longer. It can measure from very low levels of NOx up to 1500 ppm. Mainly it is used in marine diesels that are running in the ECAs of the Baltic and North Sea. Further applications are in the emission monitoring of stationary engines. The sensor principle is based on several cavities. In the first cavity the exceeding oxygen is pumped away, In the second cavity two electrodes measure a very low voltage signal that is created by reforming the NOx-content. As those currents are at a minimmum level the distance of the sensor tip to the controller is limited to 59 cm. There is a big cross-sensitivity between ammonia and NOx. Up to a level of 300 ppm it is not possible to distinguish

between both gases. Furtheron the sensor is sensitive against moisture and vapor. After starting the sensor it heats up to approximately 90C and waits for the dewpoint bit. As soon as the dew point bit has been sent by CAN-bus the ceramic will be heated up to 800C. Usually after starting the engine some seconds or even better some minutes should pass by before the dew point bit is sent. Condensating moisture on the ceramic surface will destroy the sensor immediately. Due to the oxygen pumping system it is only possible to determine a NOx-content under lean conditions. It  is not recommeded to use the sensor in Lambda = 1 engines or in gasoline engines running rich.



measuring principle

ZrO₂-based multilayer-sensor

output signal

NOx - content / binary lambda (lean/Rich) / linear lambda

supply voltage



CAN 2.0 Standard-Bus (250 kBaud, 50msec repetition)


detection open and short circuit

Exhaustgastemp.- range


measuring range for NOx

0-1500 ppm

accurancy NOx signal

@ 500 ppm 10%; @ 0 ppm 10 ppm

measuring range for oxygen

ƛ = 0,75… air

order code

Art.-Nr. 70501


Art.-No. 70550 connector kit NOx / Art.-No. 40102 welding socket SO-NOx M20x1,5

drawing part No. 70501 as PDF

NOx-Transmitter 4...20 mA

part-no. 70570

NOx-Transmitter MTH

The transmitter converts the CAN bus signal from the nitrogen oxide probe into 4-20 mA. The NOx probe also outputs the oxygen content under lean exhaust gas conditions. Both values ​​are transmitted in 4..20 mA according to a conversion table. The nitrogen oxide concentration is measured in ppm and the oxygen concentration in vol.%. Both values are given in mA. Nitrogen oxide sensors are generally are sensitive against water vapor and condensate. The risk of water hammer is greatest immediately after starting the engine. The ceramic sensor tip is heated to 800 C during measuring operation. If this is hit by a drop of water, it shatters immediately. For this reason, the probe preheats to 80 C after switching on the tip. The transmitter requests five minutes until the engine runs normally, i.e. emits little water vapor, and then sends the dew point end signal to the probe. This then heats up in stages up to the operating temperature and begins measuring the nitrogen oxide content in the exhaust gas, which will now become mA values. The transmitter is intended for top hat rail mounting and shows the operating status via status LED.


NOx-Monitoring System

Operators of a CHP system (combinedheat and power) in the European Union with a thermal output >1 MW are obliged to measure and record the nitrogen oxide concentration in the exhaust gas continuously. Most of the existing CHP engines are controlled by individual PLC controls. In combination with our transmitter it is easy to integrate the NOx-sensor in already existing and running PLC systems. One additional line for the NOx signal and another line for the oygen content are required.

NOx-Monitoring System

To integrate your NOx Monitoring System you need the parts listed underneath:

- 70501 NOx Probe

- 40102 SO-NOx welding socket to fix the sensor tip in the exhaust

SO-NOx small

- 70551 cable set with connectors and 3 m cable between sensor electronics and transmitter. Other lengths (max. 5 m) on demand.

- 70570 NOx Transmitter

Further required from customer side are:

- 24 V DC power supply with 3A (12V to 24V converter is available on demand)

- PLC control with 2 free ports 4...20 mA and knowlege how to integrate the signal input in your software.

70553 cable NOx sensor 5m