A variety of thermometers are available to parents now a days..
Electronic Ear Thermometer
Ear thermometer is not as accurate as rectal or oral/axillary thermometers. It reads the infrared heat that comes from inside of the ear. To measure temperature accurately in the ear one must pull the child’s outer ear backward before inserting the thermometer and hold the ear probe inside for approximately 2 seconds. If the child has been outside on a cold day, wait 15 minutes before measuring the ear temperature (big disadvantage). Ear infections do not affect the accuracy of an ear temperature however if there is too much wax in the ear it can interfere with correct reading. Also, if the baby is younger than three months the results might be incorrect. For older babies and children they can be quicker and easier to use though more expensive. Their use should be reserved by professionals only in a busy office practice for a quick screening.
These thermometers are not as reliable as Oral/Axillary or Rectal thermometers. Forehead thermometers (contact and non contact) are placed on the temporal artery of the forehead and will read the infrared heat that comes off of the head.
Plastic “fever” strip thermometers
They are placed on the forehead. Local sweating alters the readings significantly. These strips can not be relied on for infants and young children. They are least accurate in measurement of temperatures.
Glass thermometers that contain mercury are not recommended any more due to the potential risks of exposure to mercury if the thermometer is broken. Its use should be discouraged.
The most widely used digital thermometers for Oral or Axillary measurement are inexpensive and are fairly accurate and give minimum variations in home use by parents.
Very good knowledge improving site.