Maximum Minimum Thermometer

The maximum minimum thermometer — also known as a Six’s thermometer after its inventor James Six — records the highest and lowest temperatures reached over a period on a single instrument. It’s a staple of school and college science labs, weather stations, greenhouses and home gardens, giving a clear picture of temperature fluctuations for meteorology, environmental science and everyday monitoring.

How the maximum and minimum thermometer works

The thermometer uses a U-shaped glass tube with a temperature-sensitive liquid that expands and contracts as the temperature changes. As it moves, it pushes a small metal index up each arm of the U: one index is left at the highest (maximum) temperature reached, the other at the lowest (minimum). The indices stay in place so you can read both extremes at any time, and a magnet resets them back against the liquid to start a new reading period. Traditional models used mercury; many modern versions are mercury-free.

Dual Celsius and Fahrenheit scale

Each arm of the tube carries its own scale, and the thermometer is marked in both Celsius and Fahrenheit. This dual (double) scale makes it easy to compare readings and suits users in different regions, whether the thermometer is used in a laboratory, classroom, greenhouse or at home.

Common uses

• Recording daily maximum and minimum temperatures at weather stations
• Teaching temperature, weather and climate in schools and colleges
• Monitoring conditions in greenhouses, gardens and nurseries
• Laboratory and environmental-science measurements
• Home weather observation and general temperature tracking

How to read a maximum minimum thermometer

Read the two indices: the one in the maximum arm shows the highest temperature since the last reset, and the one in the minimum arm shows the lowest. Note both values, then hold the magnet against each index to reset it to the current temperature, ready for the next observation period.

Specifications

• Type: Six’s maximum and minimum thermometer
• Tube: U-shaped glass with two metal indices
• Scale: dual Celsius (°C) and Fahrenheit (°F)
• Frame: moulded ABS plastic
• Reset: magnet reset

Frequently asked questions

What is a maximum minimum thermometer?

It’s an instrument that records the highest (maximum) and lowest (minimum) temperatures reached over a period, usually 24 hours, so you can see how much the temperature has fluctuated.

Why is it called a Six’s thermometer?

It’s named after James Six, who invented the design in 1780. The “Six’s” maximum and minimum thermometer refers to the classic U-shaped tube that captures both temperature extremes at once.

How does a maximum and minimum thermometer work?

A temperature-sensitive liquid in a U-shaped tube expands and contracts with temperature, pushing a small metal index up each arm. One index is left at the maximum temperature and the other at the minimum, and a magnet resets them for the next reading.

Where can you use a maximum minimum thermometer?

It’s used in weather stations, schools, laboratories, greenhouses, gardens and homes to track temperature changes and teach weather and climate.

How do you read a maximum minimum thermometer?

Read the maximum index for the highest temperature and the minimum index for the lowest since the last reset. Record both, then use the magnet to reset the indices at the start of each observation period.