Troubleshooting My Avent soother thermometer readings aren't accurate. If you find the readings from the Philips Avent soother thermometer to be inaccurate, there might be a simple way to solve this. Just follow these tips and tricks. Measure longer If you take out the soother thermometer too soon the measurement will be inaccurate. Place the soother back into your baby's mouth and measure again. Wait If your baby has consumed hot or cold liquids before you measure the temperature, wait 30 minutes before you place the soother in the baby's mouth. Assembled correctly? Check that the measurement unit of the soother thermometer is firmly attached to the soother and turned completely to the closed lock position.