Low values obtained from ZMOD4410 sensor

Hi,

I'm trying to get TVOC and eCO2 from Renesas ZMOD4410 using IAQ 2nd Gen ULP. I am able to get some readings from the algorithm output, but they seem to be suspiciously low (minimal values are returned most of the time, sometimes they get increased a little bit - TVOC most of the time could increase up to around 30-40 ppb, and eCO2 up to 530 ppm. I have compared those results with readings from different TVOC sensor, and those results from other sensor were much higher (and seemed more probable). I would be grateful if you could help me with following questions:

1. Should the ZMOD4410 sensor be able to return the absolute value of TVOC at once? Or does it need to be kept in clean air for some time and only then it will be able to measure the TVOC concetration properly?

2. Are there any other common reasons for which the sensor could give too low values? 

3. I think I saw a bit ambiguous notes regarding cleaning procedure - it was mentioned that it uses sensor's NVM to store information whether the cleaning procedure has been already completed before (since it should only be performed once). On the other hand it was pointed out, that user needs to pay attention not to perform it more than once. How is it, then, can I call function for this procedure every time and assume, that sensor won't perform the cleaning if it has already been performed?

4. In my case I need to get the readings in ppb (parts per billion), according to the information I have found it seems that value in mg/m3 would need to be multiplied by approx. 531,05:

molar volume (0.024465)/ molar mass (46.069) * 10^6

Is that correct?

Parents
  • Hi Wieczorek,

    Thanks for the request. We are happy to assist you. Please see my response mentioned in green:

    1. Should the ZMOD4410 sensor be able to return the absolute value of TVOC at once? Or does it need to be kept in clean air for some time and only then it will be able to measure the TVOC concentration properly?

    >> Yes, the ZMOD needs to see the clean air for better performance. 

    ZMOD4xxx Start-Up And Stabilization Behavior | Renesas Customer Hub

    3. I think I saw a bit ambiguous notes regarding cleaning procedure - it was mentioned that it uses sensor's NVM to store information whether the cleaning procedure has been already completed before (since it should only be performed once). On the other hand, it was pointed out, that user needs to pay attention not to perform it more than once. How is it, then, can I call function for this procedure every time and assume, that sensor won't perform the cleaning if it has already been performed?

    >>The cleaning will only be executed once in the latest FW. A byte for the number of executions is saved in the sensor memory (NVM). Hence, additional execution cannot happen and are skipped. So, need to worry about that. In older version it was mentioned that not to perform more than once.

    ZMOD4xxx Cleaning Library Purpose and Usage | Renesas Customer Hub

    ZMOD4410/ZMOD4510 Run Cleaning More Than Once | Renesas Customer Hub

    4. In my case I need to get the readings in ppb (parts per billion), according to the information I have found it seems that value in mg/m3 would need to be multiplied by approx.

    >>Conversion from mg/m3 to ppm for many common TVOC is by the factor approximately 0.5 (e.g., 10mg/m3 equals approximately 5ppm). Conversion from ppm to ppb is by the factor 1000 (e.g., 0.1ppm equals 100ppb) or another way we can use the conversion formula. 

    ZMOD4410 Datasheet (renesas.com)

    ZMOD4410 Application Note - TVOC Sensing (renesas.com)

    Moreover, I have a couple of questions for our better understanding:

    1. Could you please mention that end application of your project?

    2. How long you have run our sensor and also explain where you are running our sensor (testing environment)?

    3. Please share the RMOX value or RMOX [6] that you are getting or .csv output file. 

    ZMOD4410 Raw Rmox Resistance Readings | Renesas Customer Hub

    For more information, please go through the FAQ.

    Knowledge Base | Renesas Customer Hub 

    Regards:

    Raja.


Reply
  • Hi Wieczorek,

    Thanks for the request. We are happy to assist you. Please see my response mentioned in green:

    1. Should the ZMOD4410 sensor be able to return the absolute value of TVOC at once? Or does it need to be kept in clean air for some time and only then it will be able to measure the TVOC concentration properly?

    >> Yes, the ZMOD needs to see the clean air for better performance. 

    ZMOD4xxx Start-Up And Stabilization Behavior | Renesas Customer Hub

    3. I think I saw a bit ambiguous notes regarding cleaning procedure - it was mentioned that it uses sensor's NVM to store information whether the cleaning procedure has been already completed before (since it should only be performed once). On the other hand, it was pointed out, that user needs to pay attention not to perform it more than once. How is it, then, can I call function for this procedure every time and assume, that sensor won't perform the cleaning if it has already been performed?

    >>The cleaning will only be executed once in the latest FW. A byte for the number of executions is saved in the sensor memory (NVM). Hence, additional execution cannot happen and are skipped. So, need to worry about that. In older version it was mentioned that not to perform more than once.

    ZMOD4xxx Cleaning Library Purpose and Usage | Renesas Customer Hub

    ZMOD4410/ZMOD4510 Run Cleaning More Than Once | Renesas Customer Hub

    4. In my case I need to get the readings in ppb (parts per billion), according to the information I have found it seems that value in mg/m3 would need to be multiplied by approx.

    >>Conversion from mg/m3 to ppm for many common TVOC is by the factor approximately 0.5 (e.g., 10mg/m3 equals approximately 5ppm). Conversion from ppm to ppb is by the factor 1000 (e.g., 0.1ppm equals 100ppb) or another way we can use the conversion formula. 

    ZMOD4410 Datasheet (renesas.com)

    ZMOD4410 Application Note - TVOC Sensing (renesas.com)

    Moreover, I have a couple of questions for our better understanding:

    1. Could you please mention that end application of your project?

    2. How long you have run our sensor and also explain where you are running our sensor (testing environment)?

    3. Please share the RMOX value or RMOX [6] that you are getting or .csv output file. 

    ZMOD4410 Raw Rmox Resistance Readings | Renesas Customer Hub

    For more information, please go through the FAQ.

    Knowledge Base | Renesas Customer Hub 

    Regards:

    Raja.


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