nRF91 BME680 Read The Temperature with vs without battery

[Hoang]

Dear, 

I am using THINGY:91 

I am trying to read the data from BME680 sensor:

1. config: ( i used conf file from asset_tracking)

# Sensors
CONFIG_SENSOR=n
CONFIG_BATTERY_MONITOR=y
CONFIG_ACCEL_USE_EXTERNAL=y
CONFIG_ACCEL_DEV_NAME="ADXL362"
CONFIG_ADXL362=n
CONFIG_ADXL362_TRIGGER_OWN_THREAD=n
CONFIG_ADXL362_ABS_REF_MODE=1
CONFIG_ADXL362_ACTIVITY_THRESHOLD=800
CONFIG_ADXL362_INACTIVITY_THRESHOLD=800
CONFIG_ADXL362_INTERRUPT_MODE=1

CONFIG_ENV_USE_EXTERNAL=y
CONFIG_ENV_DEV_NAME="BME680"
CONFIG_ENVIRONMENT_DATA_SEND_INTERVAL=10

CONFIG_USE_BME680_BSEC=n
CONFIG_BME680=y
CONFIG_SPI_NRFX_SPIM_MISO_NO_PULL=y

and, get the temperature: 

env_sensor_data_t env_data_m;
if (env_sensors_get_temperature(&env_data_m, NULL) == 0) {
    sprintf(tmp_tmp,"%.1f",env_data_m.value);
    printk("fTemp: %s \r\n",tmp_tmp); 
   }

It works, but I found a funny thing: 

(USB cable is connecting from THINGY:91 to my laptop to adapt outputs, and it will charge for the battery)

1. The temperatures when the THINGY:91 has and does NOT have the battery are a total difference 

   with battery                                 |                    without battery 

  31 (C)                                         ><                    24 (C)

The battery is 59(%) and of course, it is charging 

I tried to move the THINGY:91 far away from the battery, the same result. 

I tried to remove the connect THINGY and laptop ( STOP charging for battery), the value of temperatures will send to my webserver : 24 (C) ( after 10mn stable)

I am confusing: the temperature is measured on the battery or of the environment? 

Thanks., 

BR, 

Hoang Nguyen

[Kenneth]

Sounds to me that it is not the battery that is heating the circuitry, but for instance regulators and other charging circuitry the dissipate heat enough to heat up the pcb and ic during charging. 

Kenneth

[Hoang]

Kenneth said:

Sounds to me that it is not the battery that is heating the circuitry,

ja, first time, i thought the charging battery stays close to the BME sensor, but NO, I tried to move the battery far away from the sensor, the result was the same.

Kenneth said:

but for instance regulators and other charging circuitry the dissipate heat enough to heat up the pcb and ic during charging. 

looks like that. you need to check again  by yourself and if the same problem, it will be a bug for pcb design 

[Hoang]

what do you think  Kenneth?

[Kenneth]

It's a valid point, and I have asked the team to consider adding a note in documentation that charging circuitry should be moved away from the temperature sensor in a final design to avoid dissipating heat to reach the temperature sensor. May also need to consider wrapping of the plastic casing may be keeping heat inside the closure.