MH-Z14A CO2 sensor



  • Re: MH-Z14A CO2 sensor

    I need to use this sensor but there is very little documentation on the flying lead header pitch. i need to use a connector that will securely fit the flying wire off of the sensor board to my PCB. but i don't know the pitch it is using, from pictures it looks like either the 1.27mm pitch or 1.5mm pitch. Can someone who has this sensor please help me?

    I would also be very interested in what each colour of the flying wire corresponds to which signal.

    cheers,


  • Mod

    Let's bring this thread to @alexsh1's attention



  • This has all the information i need:
    1.25mm pitch (i'm assuming for 7pins it should be interchangeable with a 1.27mm pitch)

    also from left to right: PWM, Tx, Rx, VCC, GND, AOUT, HD

    https://web.opendrive.com/api/v1/download/file.json/NDVfMzUyMzMyM18?inline=0



  • I am glad you work it out yourself
    I think when it comes to this sensor everything is well documented or available in the Internet


  • Hardware Contributor

    The sensor is really simple to use, when attached via serial-ttl (3.3V) and powered with 5 volt.

    MH-Z14 co2 readings - PWM & UART with raspberry pi in C++ – 16:21
    — Gary Travell

    You get the values directly from the sensor and don't need to make calculations. Here is what I use:

    /*
       The MySensors Arduino library handles the wireless radio link and protocol
       between your home built sensors/actuators and HA controller of choice.
       The sensors forms a self healing radio network with optional repeaters. Each
       repeater and gateway builds a routing tables in EEPROM which keeps track of the
       network topology allowing messages to be routed to nodes.
    
       Created by Henrik Ekblad <henrik.ekblad@mysensors.org>
       Copyright (C) 2013-2015 Sensnology AB
       Full contributor list: https://github.com/mysensors/Arduino/graphs/contributors
    
       Documentation: http://www.mysensors.org
       Support Forum: http://forum.mysensors.org
    
       This program is free software; you can redistribute it and/or
       modify it under the terms of the GNU General Public License
       version 2 as published by the Free Software Foundation.
    
     *******************************
    
       DESCRIPTION
    
        MH-Z14 CO2 sensor via rx/tx serial
    
        */
    
    // Enable debug prints to serial monitor
    //#define MY_DEBUG
    
    // Enable and select radio type attached
    //#define MY_RADIO_NRF24
    
    #define MY_RADIO_RFM69
    #define MY_RFM69_FREQUENCY RF69_868MHZ
    #define MY_RFM69_NETWORKID 13
    #define MY_RFM69_ENABLE_ENCRYPTION
    #define MY_IS_RFM69HW
    
    #include <MySensors.h>
    #include <SoftwareSerial.h>
    #include <Wire.h>
    #include "Adafruit_HTU21DF.h"
    
    SoftwareSerial mySerial(A0, A1); // RX, TX соответственно
    
    Adafruit_HTU21DF htu = Adafruit_HTU21DF();
    
    byte cmd[9] = {0xFF, 0x01, 0x86, 0x00, 0x00, 0x00, 0x00, 0x00, 0x79};
    char response[9];
    
    #define CHILD_ID_AIQ 0
    #define CHILD_ID_TEMP  1
    #define CHILD_ID_HUM   2
    
    unsigned long SLEEP_TIME = 30 * 1000; // Sleep time between reads (in milliseconds)
    unsigned int TEMP_HUM_ROUNDS = 5; // wait 5 rounds for sending TEMP_HUM
    unsigned int loop_round = 0;
    boolean preheat = true;  // wait TEMP_HUM_ROUNDS for preheat
    
    int lastppm = 0;
    
    MyMessage msg(CHILD_ID_AIQ, V_LEVEL);
    MyMessage msg2(CHILD_ID_AIQ, V_UNIT_PREFIX);
    MyMessage msgHum(CHILD_ID_HUM, V_HUM);
    MyMessage msgTemp(CHILD_ID_TEMP, V_TEMP);
    
    boolean isMetric = true;
    
    void setup()
    {
      mySerial.begin(9600);
      isMetric = getConfig().isMetric;
    
      if (!htu.begin()) {
        Serial.println("Couldn't find sensor htu21!");
      }
    }
    
    void presentation() {
      // Send the sketch version information to the gateway and Controller
      sendSketchInfo("AIQ Sensor CO2 MH-Z14 Serial, HTU21 Temp Hum", "1.0");
    
      // Register all sensors to gateway (they will be created as child devices)
      present(CHILD_ID_AIQ, S_AIR_QUALITY);
      send(msg2.set("ppm"));
    
      present(CHILD_ID_TEMP, S_TEMP);
      present(CHILD_ID_HUM, S_HUM);
    }
    
    void loop() {
    
      mySerial.write(cmd, 9);
      mySerial.readBytes(response, 9);
      int responseHigh = (int) response[2];
      int responseLow = (int) response[3];
      int ppm = (256 * responseHigh) + responseLow;
    
      if ((loop_round == 0) || (abs(ppm - lastppm) >= 10)) {
        if (!preheat) {
          send(msg.set(ppm));
          lastppm = ppm;
        }
      }
    
    
    
      if (loop_round == 0) {
        float temp = htu.readTemperature();
        if (!isMetric) {
          temp = temp * 9 / 5 + 32; // convert to farenheit
        }
        send(msgTemp.set(temp, 1));
    
        float hum = htu.readHumidity();
        send(msgHum.set(hum, 1));
      }
    
      loop_round++;
      if (loop_round >= TEMP_HUM_ROUNDS) {
        loop_round = 0;
        preheat = false;
      }
    
      // Power down the radio.  Note that the radio will get powered back up
      // on the next write() call.
      sleep(SLEEP_TIME); //sleep for: sleepTime
    }
    

  • Hero Member

    Thanks @FotoFieber for providing the information how to read the MH-Z14 via serial communication.
    Works like a charm.


  • Hero Member

    Seems like my MH-Z14 sensor is faulty after all. My problem was that the sensor reported the value 562 like 80% of the time. I was hoping I could solve this by using the serial method to read the value from the sensor but I stil had the same problem. Luckily I just received another MH-Z14 so I could replace it. Now it seems to work better.


  • Hardware Contributor

    @korttoma
    It is working like a charme for me. Important is, to have 5V for voltage and 3.3 V on the logical level. Here is a graf, the green "Badezimmer" line is the mysensors sensor with MH-Z14A, the others are from netatmo. The mysensors sensor is in the bathroom and therefore it will have usually less CO2.

    0_1479399795680_co2.JPG


  • Hero Member

    @FotoFieber My new sensor is giving me the exact same behaivour. Could it be that the problem is that I'm using a 5V Pro Mini?


  • Hardware Contributor

    @korttoma said:

    @FotoFieber My new sensor is giving me the exact same behaivour. Could it be that the problem is that I'm using a 5V Pro Mini?

    Yes. You have to use a 3.3V arduino and power the sensor with 5V (seperate voltage). The sensor may break with a 5V arduino. I use a 3.3V 8 MHz pro mini.


  • Hero Member

    @FotoFieber

    So the symptom I see as the sensor constantly reporting the value 562 could be because it is already broken?
    Or would a broken sensor just stop communicating via serial?


  • Hardware Contributor

    @korttoma
    As I do not have a broken sensor, I can not tell you.
    If I were you, I would try to fix the voltage issues and check, if it is working then.

    The sensor requires a preheat. Have you used my sketch from above?


  • Hero Member

    @FotoFieber I swapped out the 5V Pro Mini with a 3.3V Pro Mini yesterday and I'm afraid it did not help at all. If the Sensor would have had a problem with the 5V on the serial pins I bet it would no longer communicate.

    I used some parts of your sketch but since I use an Si7021 and a different radio I had to do some modifications:

    /**
     * The MySensors Arduino library handles the wireless radio link and protocol
     * between your home built sensors/actuators and HA controller of choice.
     * The sensors forms a self healing radio network with optional repeaters. Each
     * repeater and gateway builds a routing tables in EEPROM which keeps track of the
     * network topology allowing messages to be routed to nodes.
     *
     * Created by Henrik Ekblad <henrik.ekblad@mysensors.org>
     * Copyright (C) 2013-2015 Sensnology AB
     * Full contributor list: https://github.com/mysensors/Arduino/graphs/contributors
     *
     * Documentation: http://www.mysensors.org
     * Support Forum: http://forum.mysensors.org
     *
     * This program is free software; you can redistribute it and/or
     * modify it under the terms of the GNU General Public License
     * version 2 as published by the Free Software Foundation.
     *
     *******************************
     *
     * DESCRIPTION
     *
     *  MH-Z14 CO2 sensor
     * 
     *  Wiring:
     *   Pad 1, Pad 5: Vin (Voltage input 4.5V-6V) 
     *   Pad 2, Pad 3, Pad 12: GND 
     *   Pad 6: PWM output ==> pin 6
     *
     *  From: http://davidegironi.blogspot.fr/2014/01/co2-meter-using-ndir-infrared-mh-z14.html
     *    MH-Z14 has a PWM output, with a sensitivity range of 0ppm to 2000ppm CO2, an accurancy of ±200ppm.
     *    The cycle is 1004ms±5%, given the duty cicle Th (pulse high), Tl is 1004-Th, we can convert it to CO2 value using the formula:
     *    CO2ppm = 2000 * (Th - 2ms) /(Th + Tl - 4ms)
     *  From: http://airqualityegg.wikispaces.com/Sensor+Tests
     *    - response time is less than 30 s
     *   - 3 minute warm up time
     *  datasheet: 
     * 
    * Contributor: epierre
    **/
    //#define MY_DEBUG 
    
    #define MY_RADIO_NRF24
    
    #define MY_NODE_ID  6
    #define SN "AIQ CO2 MH-Z14 TxRx"
    #define SV "2.1"
    #define MY_BAUD_RATE  9600
    #include <MyConfig.h>
    #include <MySensors.h>
    #include <Wire.h>
    #include <SI7021.h>
    #include <SPI.h>
    #include <RunningAverage.h>
    #include <SoftwareSerial.h>
    // Define a static node address, remove if you want auto address assignment
    
    SoftwareSerial mySerial(6, 7); // RX, TX
    
    byte cmd[9] = {0xFF, 0x01, 0x86, 0x00, 0x00, 0x00, 0x00, 0x00, 0x79};
    char response[9];
    
    // Child sensor ID's
    #define CHILD_ID_AIQ 1
    #define CHILD_ID_HUM   2
    #define CHILD_ID_TEMP  3
    
    //#define AIQ_SENSOR_ANALOG_PIN 5
    
    // TEMP_TRANSMIT_THRESHOLD for temperature threshold.
    #define HUMI_TRANSMIT_THRESHOLD 0.5
    #define TEMP_TRANSMIT_THRESHOLD 0.5
    #define AVERAGES 2
    
    unsigned long SLEEP_TIME = 30000; // Sleep time between reads (in milliseconds)
    
    float valAIQ =0.0;
    float lastAIQ =0.0;
    unsigned int loop_round = 0;
    int lastppm = 0;
    boolean preheat = true;  // wait TEMP_HUM_ROUNDS for preheat
    
    SI7021 humiditySensor;
    
    
    MyMessage msg(CHILD_ID_AIQ, V_LEVEL);
    MyMessage msg2(CHILD_ID_AIQ, V_UNIT_PREFIX);
    MyMessage msgHum(CHILD_ID_HUM, V_HUM);
    MyMessage msgTemp(CHILD_ID_TEMP, V_TEMP);
    
    // Global settings
    
    boolean isMetric = true;
    
    
    // Storage of old measurements
    float lastTemperature = -100;
    int lastHumidity = -100;
    
    RunningAverage raHum(AVERAGES);
    
    void setup()  
    {
    
      mySerial.begin(9600);
        
      humiditySensor.begin();
      
      sleep(SLEEP_TIME);
      
      //pinMode(AIQ_SENSOR_ANALOG_PIN, INPUT);
      
      isMetric = getConfig().isMetric;
      Serial.print(F("isMetric: ")); Serial.println(isMetric);
      raHum.clear();
         wait(200);
    
      send(msg2.set("ppm"));
    }
    
    void presentation()  
    { 
     // Send the sketch version information to the gateway and Controller
      
      sendSketchInfo(SN, SV);
      // Register all sensors to gateway (they will be created as child devices)
      present(CHILD_ID_AIQ, S_AIR_QUALITY);
      present(CHILD_ID_TEMP,S_TEMP);
      present(CHILD_ID_HUM,S_HUM);
    
      wait(200);
    
      send(msg2.set("ppm"));
    }
    
    void loop() { 
    
    
        mySerial.write(cmd, 9);
      mySerial.readBytes(response, 9);
      int responseHigh = (int) response[2];
      int responseLow = (int) response[3];
      int co2ppm = (256 * responseHigh) + responseLow;
      Serial.print(F("c02ppm :"));Serial.println(co2ppm);
      if ( (abs(co2ppm - lastppm) >= 10)) {
       
          send(msg.set(co2ppm));
          lastppm = co2ppm;
        
      }
      
      
      si7021_env data = humiditySensor.getHumidityAndTemperature();
      
      raHum.addValue(data.humidityPercent);
      
      float diffTemp = abs(lastTemperature - (isMetric ? data.celsiusHundredths : data.fahrenheitHundredths)/100.0);
      float diffHum = abs(lastHumidity - raHum.getAverage());
    
      Serial.print(F("TempDiff :"));Serial.println(diffTemp);
      Serial.print(F("HumDiff  :"));Serial.println(diffHum); 
    
      
      if (diffTemp > TEMP_TRANSMIT_THRESHOLD) {
        float temperature = (isMetric ? data.celsiusHundredths : data.fahrenheitHundredths) / 100.0;
        Serial.print("T: ");Serial.println(temperature);
        send(msgTemp.set(temperature,1));
        lastTemperature = temperature;
      }
      if (diffHum > HUMI_TRANSMIT_THRESHOLD) {
        int humidity = data.humidityPercent;
        
        Serial.print("H: ");Serial.println(humidity);
            
        send(msgHum.set(humidity));
        
        lastHumidity = humidity;
        
      }
    
      
      //Serial.println();
      
      // Power down the radio.  Note that the radio will get powered back up
      // on the next write() call.
      sleep(SLEEP_TIME); //sleep for: sleepTime
    }
    

    I hope I made a mistake in the sketch since I'm running out of ideas and I don't want the sensors to be broken.
    From where did you buy your sensor? I got them from aliexpress...


  • Hardware Contributor

    @korttoma
    Where is the preheat logic in your sketch?

    Values in the preheat time could be wrong....


  • Hero Member

    @FotoFieber Yeah, I don't have preheat logic but that would only account for values when I first plug it in. I get the strange values even if it has been running for weeks. I will try to get a graph of what I see this evening so you can see what I mean. I'm seriously considering to just exclude the value 562 from being sent to the controller.



  • @korttoma Sounds like you have a faulty sensor. Did you try analogue output? This is just to make sure the sensor is working.

    There are PWM or UART.
    Did you try both of them? I am using 5V Arduino Nano with no problem.

    The digital pins communicate via PWM or UART. Output (and input for UART) of these ports work on 3.3 Volts - this means you should change the ARef of your Arduino - or rescale your values
    
    

  • Hero Member

    0_1479910781525_InluftCO2.JPG



  • @korttoma try to put it outside for some time to recalibrate. If it does not help, you may need to calibrate it.

    Or you just got a bad one.


  • Hero Member

    @alexsh1 Will the sensor really recalibrate by itself if I put it outside?

    I could send a "zero calibration" command via serial but then I would need to "input Nitrogen gas for 5 minutes when make zero calibration. "

    Instead of exposing it to nitrogen gas could I just like you said put it outside and then send the "zero calibration" command?

    To do the " span calibration" I would need to know what kind of values to send to it and I have no idea.

    btw, here are some values I read now via serial at the office (I do not get the 562 value so far) but does these values seem reasonable for a well ventilated office?

    
    HiResp :3
    LoResp :-21
    Tem.channel :63
    c02ppm :747 
    
    HiResp :3
    LoResp :124
    Tem.channel :63
    c02ppm :892
    
    
    HiResp :3
    LoResp :21
    Tem.channel :63
    c02ppm :789
    
    HiResp :2
    LoResp :-57
    Tem.channel :63
    c02ppm :455
    
    HiResp :2
    LoResp :-110
    Tem.channel :63
    c02ppm :402
    
    HiResp :2
    LoResp :99
    Tem.channel :63
    c02ppm :611
    
    HiResp :2
    LoResp :51
    Tem.channel :63
    c02ppm :563
    
    HiResp :2
    LoResp :20
    Tem.channel :63
    c02ppm :532
    
    HiResp :1
    LoResp :-2
    Tem.channel :63
    c02ppm :254
    
    HiResp :1
    LoResp :-32
    Tem.channel :63
    c02ppm :224
    
    HiResp :1
    LoResp :-55
    Tem.channel :63
    c02ppm :201
    
    HiResp :1
    LoResp :-68
    Tem.channel :63
    c02ppm :188
    
    HiResp :1
    LoResp :-75
    Tem.channel :63
    c02ppm :181
    
    HiResp :1
    LoResp :-79
    Tem.channel :63
    c02ppm :177
    
    HiResp :1
    LoResp :-98
    Tem.channel :63
    c02ppm :158
    
    HiResp :1
    LoResp :-102
    Tem.channel :63
    c02ppm :154
    
    HiResp :1
    LoResp :-109
    Tem.channel :63
    c02ppm :147
    
    HiResp :1
    LoResp :-116
    Tem.channel :63
    c02ppm :140
    
    HiResp :1
    LoResp :-125
    Tem.channel :63
    c02ppm :131
    
    HiResp :1
    LoResp :-124
    Tem.channel :63
    c02ppm :132
    
    HiResp :1
    LoResp :111
    Tem.channel :63
    c02ppm :367
    
    HiResp :1
    LoResp :115
    Tem.channel :63
    c02ppm :371
    
    HiResp :1
    LoResp :121
    Tem.channel :63
    c02ppm :377
    
    HiResp :1
    LoResp :114
    Tem.channel :63
    c02ppm :370
    
    HiResp :1
    LoResp :-62
    Tem.channel :63
    c02ppm :194
    
    HiResp :1
    LoResp :-7
    Tem.channel :63
    c02ppm :249
    
    HiResp :1
    LoResp :-53
    Tem.channel :63
    c02ppm :203
    
    HiResp :1
    LoResp :-68
    Tem.channel :63
    c02ppm :188
    
    HiResp :1
    LoResp :-96
    Tem.channel :63
    c02ppm :160
    
    HiResp :1
    LoResp :-111
    Tem.channel :63
    c02ppm :145
    
    HiResp :1
    LoResp :-121
    Tem.channel :63
    c02ppm :135
    
    HiResp :1
    LoResp :-127
    Tem.channel :63
    c02ppm :129
    
    HiResp :1
    LoResp :-124
    Tem.channel :63
    c02ppm :132
    
    HiResp :1
    LoResp :-126
    Tem.channel :63
    c02ppm :130
    
    HiResp :1
    LoResp :-126
    Tem.channel :63
    c02ppm :130
    
    HiResp :1
    LoResp :-110
    Tem.channel :63
    c02ppm :146
    
    HiResp :1
    LoResp :-110
    Tem.channel :63
    c02ppm :146
    
    HiResp :1
    LoResp :-60
    Tem.channel :63
    c02ppm :196
    
    HiResp :1
    LoResp :-69
    Tem.channel :63
    c02ppm :187
    
    HiResp :1
    LoResp :-101
    Tem.channel :63
    c02ppm :155
    
    HiResp :1
    LoResp :-104
    Tem.channel :63
    c02ppm :152
    
    HiResp :1
    LoResp :-114
    Tem.channel :63
    c02ppm :142
    
    HiResp :1
    LoResp :-128
    Tem.channel :63
    c02ppm :128
    
    HiResp :1
    LoResp :-122
    Tem.channel :63
    c02ppm :134
    
    HiResp :1
    LoResp :122
    Tem.channel :63
    c02ppm :378
    
    HiResp :1
    LoResp :119
    Tem.channel :63
    c02ppm :375
    
    HiResp :1
    LoResp :-128
    Tem.channel :63
    c02ppm :128
    
    HiResp :1
    LoResp :-86
    Tem.channel :63
    c02ppm :170
    
    HiResp :1
    LoResp :-110
    Tem.channel :63
    c02ppm :146
    
    HiResp :1
    LoResp :-123
    Tem.channel :63
    c02ppm :133
    
    HiResp :1
    LoResp :-101
    Tem.channel :63
    c02ppm :155
    
    HiResp :1
    LoResp :-75
    Tem.channel :63
    c02ppm :181
    
    HiResp :1
    LoResp :-92
    Tem.channel :63
    c02ppm :164
    
    HiResp :1
    LoResp :-101
    Tem.channel :63
    c02ppm :155
    
    HiResp :1
    LoResp :-123
    Tem.channel :63
    c02ppm :133
    
    HiResp :1
    LoResp :-114
    Tem.channel :63
    c02ppm :142
    
    HiResp :1
    LoResp :-127
    Tem.channel :63
    c02ppm :129
    
    HiResp :1
    LoResp :-120
    Tem.channel :63
    c02ppm :136
    
    HiResp :1
    LoResp :126
    Tem.channel :63
    c02ppm :382
    
    HiResp :1
    LoResp :118
    Tem.channel :63
    c02ppm :374
    
    HiResp :1
    LoResp :-127
    Tem.channel :63
    c02ppm :129
    
    HiResp :1
    LoResp :118
    Tem.channel :63
    c02ppm :374
    
    HiResp :1
    LoResp :120
    Tem.channel :63
    c02ppm :376
    
    HiResp :1
    LoResp :118
    Tem.channel :63
    c02ppm :374
    
    HiResp :1
    LoResp :115
    Tem.channel :63
    c02ppm :371
    
    HiResp :1
    LoResp :124
    Tem.channel :63
    c02ppm :380
    
    HiResp :1
    LoResp :120
    Tem.channel :63
    c02ppm :376
    
    HiResp :1
    LoResp :-119
    Tem.channel :63
    c02ppm :137
    
    HiResp :1
    LoResp :-126
    Tem.channel :63
    c02ppm :130
    
    HiResp :1
    LoResp :-127
    Tem.channel :63
    c02ppm :129
    
    HiResp :1
    LoResp :-124
    Tem.channel :63
    c02ppm :132
    
    HiResp :1
    LoResp :121
    Tem.channel :63
    c02ppm :377
    
    HiResp :1
    LoResp :114
    Tem.channel :63
    c02ppm :370
    
    HiResp :1
    LoResp :108
    Tem.channel :63
    c02ppm :364
    
    HiResp :1
    LoResp :108
    Tem.channel :63
    c02ppm :364
    
    HiResp :1
    LoResp :119
    Tem.channel :63
    c02ppm :375
    
    HiResp :1
    LoResp :-110
    Tem.channel :63
    c02ppm :146
    
    HiResp :1
    LoResp :124
    Tem.channel :63
    c02ppm :380
    
    HiResp :1
    LoResp :127
    Tem.channel :63
    c02ppm :383
    
    HiResp :1
    LoResp :-43
    Tem.channel :63
    c02ppm :213
    
    HiResp :1
    LoResp :-72
    Tem.channel :63
    c02ppm :184
    
    HiResp :1
    LoResp :-77
    Tem.channel :63
    c02ppm :179
    
    HiResp :1
    LoResp :-63
    Tem.channel :63
    c02ppm :193
    
    HiResp :1
    LoResp :-92
    Tem.channel :63
    c02ppm :164
    
    HiResp :1
    LoResp :-105
    Tem.channel :63
    c02ppm :151
    
    HiResp :1
    LoResp :-116
    Tem.channel :63
    c02ppm :140
    
    HiResp :2
    LoResp :41
    Tem.channel :63
    c02ppm :553
    
    HiResp :2
    LoResp :47
    Tem.channel :63
    c02ppm :559
    
    HiResp :2
    LoResp :26
    Tem.channel :63
    c02ppm :538
    
    HiResp :2
    LoResp :-107
    Tem.channel :63
    c02ppm :405
    
    HiResp :2
    LoResp :-76
    Tem.channel :63
    c02ppm :436
    
    HiResp :2
    LoResp :-97
    Tem.channel :63
    c02ppm :415
    
    HiResp :2
    LoResp :-109
    Tem.channel :63
    c02ppm :403
    
    HiResp :2
    LoResp :106
    Tem.channel :63
    c02ppm :618
    
    HiResp :2
    LoResp :-96
    Tem.channel :63
    c02ppm :416
    
    HiResp :2
    LoResp :80
    Tem.channel :63
    c02ppm :592
    
    HiResp :2
    LoResp :69
    Tem.channel :63
    c02ppm :581
    
    HiResp :2
    LoResp :40
    Tem.channel :63
    c02ppm :552
    
    HiResp :2
    LoResp :84
    Tem.channel :63
    c02ppm :596
    
    HiResp :2
    LoResp :45
    Tem.channel :63
    c02ppm :557
    
    HiResp :2
    LoResp :3
    Tem.channel :63
    c02ppm :515
    
    HiResp :1
    LoResp :-30
    Tem.channel :63
    c02ppm :226
    
    HiResp :1
    LoResp :-62
    Tem.channel :63
    c02ppm :194
    
    HiResp :1
    LoResp :-73
    Tem.channel :63
    c02ppm :183
    
    HiResp :1
    LoResp :-75
    Tem.channel :63
    c02ppm :181
    
    HiResp :1
    LoResp :-96
    Tem.channel :63
    c02ppm :160
    
    HiResp :1
    LoResp :-89
    Tem.channel :63
    c02ppm :167
    
    HiResp :1
    LoResp :-101
    Tem.channel :63
    c02ppm :155
    
    HiResp :1
    LoResp :-112
    Tem.channel :63
    c02ppm :144
    
    HiResp :1
    LoResp :-107
    Tem.channel :63
    c02ppm :149
    
    HiResp :1
    LoResp :-112
    Tem.channel :63
    c02ppm :144
    
    HiResp :1
    LoResp :-110
    Tem.channel :63
    c02ppm :146
    
    HiResp :1
    LoResp :-124
    Tem.channel :63
    c02ppm :132
    
    HiResp :1
    LoResp :-120
    Tem.channel :63
    c02ppm :136
    
    HiResp :1
    LoResp :-75
    Tem.channel :63
    c02ppm :181
    

    Some of the values seem a bit low to me. Especially while the HiResp is 1 or the LoResp is negative.

    I will do this test again at home when I get the chance.


  • Hardware Contributor

    @korttoma
    In the technical specification I only find the calibration with nitrogen. I don't think, that putting it outside, will help, as it is usually at around 400 ppm at the moment. (AFAIK netatmo sets the lowest measured value in the last one or two weeks to 400 for calibration).


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