Evaluation of analytical parameters of electrochemical ammonia gas sensors provided by N.E.T. S.r.l. – a report by RUBIX S&I

Our PREMIUM LINE of Electrochemical cells has been designed with optimal performance and superior reliability in mind, in order to respond to the common challenges of industrial safety gas detection, even in harsh environments. In fact, the PREMIUM LINE meet or exceed the performance requirements of European Standard EN 45544-2 (Workplace atmospheres. Electrical apparatus used for the direct detection and direct concentration measurement of toxic gases and vapours. Performance requirements for apparatus used for exposure measurement).

The performances of our Ammonia (NH3) cell are particularly strong when compared to most alternatives available on the market. It has great resistance to a light presence of ammonia in the environment and a capability of recovering sensitivity after high exposures, dramatically reducing calibration and substitution frequency. It has also low cross-sensitivity with other gases.

Last spring, our valued customer RUBIX Senses & Instrumentation has taken the care to independently test our 0-100 ppm Ammonia sensor performances against two others with identical range. We hereby publish the complete report of the tests for the benefit of other users.

The whole N.E.T. organization wish to heartily thank RUBIX S&I for sharing the test results and allowing it to be released on our website.

About RUBIX Senses & Instrumentation

RUBIX S&I is an analytical company dedicated to monitoring different forms of pollution indoors and outdoors – with a portfolio of micro-sensors and algorithms – to improve security and wellness at work. The company has an experience of more than 100 man/years in the field of sensors and particularly gas sensors, COV and smells.

RUBIX S&I is one of today’s leaders in monitoring wellness and comfort with an on-line follow-up of cartographies of the inside or outside of buildings, of physical, chemical and biological pollution. RUBIX S&I also uses its expertise to develop miniaturized bespoke multi-sensor modules used for the environment, smart homes or health sector.  More information on www.rubixsi.com

 

Report

Evaluation of analytical parameters of electrochemical ammonia gas sensors provided by N.E.T. S.r.l.,”

 

Object:  Evaluation of analytical parameters of electrochemical ammonia gas sensors from N.E.T. (denotes as NET), supplier A (denotes as Sensor A), supplier B (denotes as Sensor B) with identical detection range 0-100 ppm NH3.

Conditions

All tests were realized at RH: 45±5% , T: 21±2°C in ambient air with addition of certificated gas mixtures from AirProducts:

H2S : N2 – 79.1% vol, O2 – 20.91 %vol, H2S – 25.3 ppm.

NH3 : N2 – 79.1% vol, O2 – 20.89 %vol, NH3 – 27.5 ppm.

Report composition.

  1. Calibration of N.E.T sensors
  2. Evaluation of cross sensitivity of N.E.T sensors to H2S injection.
  3. Simultaneous evaluation of sensors from different supplier sensors to H2S injection.
  1. Calibration of NET sensors

Unpacked sensors were installed into evaluation test bench – in enclosed controlled volume chamber.  After 15 min of signal stabilization the calculated volumes of NH3-air mixture was injected into the test chamber.  Measured value was taken 60 second after injection.  Calibration of NET NH3 sensors are presented below.

Fig 1. Calibration of NET HN3 sensors

Tested sensors show good linear behavior with small average deviation <5%

 

 

 

 

 

 

 

2. Evaluation of cross sensitivity of N.E.T sensors to H2S injection.

Sensors were installed into evaluation test bench – in enclosed controlled volume chamber. After 35 min of signal stabilization the calculated volumes of H2S-air mixture was injected into the test chamber. Continuous measurements are presented below. Simultaneous detection of H2S presence was controlled by H2S selective sensor.

Fig 2. Evaluation of cross-sensitivity to 1, 2 and 5 ppm of H2S of N.E.T. Sensors.

Tested sensors show reproducible and weak variation of output signal at presence up to 5 ppm H2S.

 

 

 

 

 

 

 

3. Simultaneous evaluation of sensors from different supplier to H2S.

Sensors from N.E.T and supplier A and B (denotes as Sensor A and Sensor B) were installed into evaluation test bench – in enclosed controlled volume chamber. After 2h of signal stabilization the calculated volumes of H2S-air mixture were injected into the test chamber. Continuous measurements are presented below on Fig 3. Simultaneous detection of H2S presence was controlled by two H2S selective sensor.

Fig 3. Evaluation of cross-sensitivity to 3, 5.7 and 8 ppm of H2S of NH3 sensors from N.E.T., Suppliers A and B.

Fig 4. Evaluation of sensitivity to NH3 and cross-sensitivity to H2S and sensors from N.E.T., Suppliers A and B

Sensors B and N.E.T. shows good, linear sensitivity to NH3, contrary to Sensor A which is not correctly linear, at same time control H2S sensors are not sensitive to HN3. In presence of H2S signal from sensors A and B increase and follow concentration of H2S. At same time NET sensors shows smooth negative response as denotes in original datasheet. Comparative table represent important advantage or NET NH3 sensor in selectivity contrary to sensors A and B. Comparative table of tested sensors

 

Sensor Comparative signal amplitude at 5 ppm NH3 Reading in ppm NH3 at 5.7 ppm H2S
NET 100 % -0.5
Sensor A 203 % 4.1
Sensor B 109 % 5.4

 

General conclusions

Evaluated ammonia sensors provides from N.E.T. srl. tested by RUBIX SI confirms their analytical characteristics in tests of repeatability and cross-sensitivity vs H2S. The N.E.T. sensors were simultaneously tested and compared to concurrent sensors from Suppliers A and B. Notwithstanding a smaller output signal, the NET sensors has much lower interference to H2S. According to original data obtained by RUBIX SI the NET NH3 sensors could be used for measurement of ammonia in presence up to 5 ppm H2S with average error ≤10% in range 0-10 ppm of NH3.

Notes: *bin – in our digital measuring circuit we use binary number as signal. You can consider the 25000 units as 0 µA of current.