How accurate is die temperature using sd_temp_get()

[Antonio]

Hi,

I am measuring die temperature of the nRF51822 using sd_temp_get() at the timeout handler of the RTC1 timer every 2 seconds.

I am using the battery service for a quick test.

After dividing the result by 4 I am getting 39 C (0x27 at the master control panel) when the room temperature is 26.

Am I doing something wrong?

Thanks,

This is a piece of my code:

static void battery_level_update(void) { uint32_t err_code; int32_t p_temp; uint8_t temperature;

	err_code = sd_temp_get(&p_temp);
            APP_ERROR_CHECK(err_code);
	temperature = (uint8_t)(p_temp / 4) ;

err_code = ble_bas_battery_level_update(&m_bas, temperature);
if ((err_code != NRF_SUCCESS) &&
    (err_code != NRF_ERROR_INVALID_STATE) &&
    (err_code != BLE_ERROR_NO_TX_BUFFERS) &&
    (err_code != BLE_ERROR_GATTS_SYS_ATTR_MISSING)
)
{
    APP_ERROR_HANDLER(err_code);
}

}

[FormerMember]

Well, the datasheet says that the temperature sensor peripheral is +/- 4 C accurate in its measurement. I was also surprised when i first saw it showing a lot more than room temperature. As an experiment, you could unplug it for sometime so that it is in room temperature so that you can see if the value increases after running for a while.