Wireless Air Quality Sensor PR55-45L iaq, gas resistance not changing

Hardware
1

I have two Industrial IoT Long Range Wireless Environmental Temperature Humidity Pressure Air Quality Sensors (PR55-45L) installed and configured, currently streaming to our cloud database using an mqtt gateway.

Since installation I have been watching air temperature, humidity, and pressure behave normally, but the air quality and gas resistance measurements have never moved from their default pre-warm up measurements. I have power cycled both devices with 30min+ wait times before checking many times, and I’ve swapped probes.

These sensors are currently active, they’ve been online for weeks uninterrupted.

Sensor 1:

{macaddress:{"firmware_version":3,"transmission_count":158,"reserve_byte":0,"battery_level":3.29406,"type":27,"node_id":2,"rssi":25,"temperature":4.39,"pressure":952.58,"humidity":51.6,"gas_resistance":1.297691e7,"iaq":21}}

sensor 2:

{macaddress:{"firmware_version":3,"transmission_count":170,"reserve_byte":0,"battery_level":3.29406,"type":27,"node_id":0,"rssi":100,"temperature":35.22,"pressure":951.54,"humidity":6.984,"gas_resistance":1.297691e7,"iaq":21}}

Can you please help me determine why the iaq and gas resistance measurements are not working? Thank you.

2

its quite strange that both are reading same gas resistance.

@TravisE_NCD_Technica can you check the data decoding in the gateway ?

3

This is the parsing code for the Type 27 Air quality sensor in the MQTT Micro Gateway. Let me know if anything looks out of place.

case(27):{
  if(len < 25){
    return false;
  }
  if(newDevice){
    json["Type"] = "Environmental";
    json["SKU"] = "";
  }
  dataObject["temperature"] = (float)signedInt(data, 9, 16) / 100.00;
  dataObject["pressure"] = (float)((data[11]<<24)+(data[12]<<16)+(data[13]<<8)+data[14]) / 100.00;
  dataObject["humidity"] = (float)((data[15]<<24)+(data[16]<<16)+(data[17]<<8)+data[18]) / 1000.00;
  dataObject["gas_resistance"] = (float)((data[19]<<24)+(data[20]<<16)+(data[21]<<8)+data[22]);
  dataObject["iaq"] = (float)(data[23]<<8)+data[24];
  rDevice = true;
  break;
}
4

are the sensor installed a clean area ? if yes than the AQI value could be same.
if you put the sensor in dirty environment does the AQI values change ?

5

There are two sensors. One is installed in a dirty work environment (expected iaq low). The second is installed in a large cooler room that is totally clean with clean air (expected iaq high). There is reason to believe that the air quality would be noticeably worse than average clean air in the dirty work environment.

If the iaq readings were correct at 21 each, I find it very hard to believe that those numbers have never changed over thousands of automated messages out. In addition, the gas resistance also has not changed and shows an identical problem–there is no way that the gas resistance numbers should be equal.

Thanks,
Robby

6

Yes its an unusual case. We will run a test witj mqtt gateway over here.

7

Thank you Bhaskar and Travis for your support. Please let me know if I can provide any additional details to help replicate this finding.

8

Travis has the hardware, we will work on replicating it today/tomorrow