Maximum Minimum Thermometers

How to read the thermometer

The minimum temperature is read on the left hand side – note red indicates below freezing point

The maximum temperature is read on the right hand side – black indicates above freezing point

A		Current temperature top of the mercury – arrow 1 – 5°C Minimum temperature bottom of left blue metal float – arrow 2 -2°C Maximum temperature bottom of right blue metal float – arrow 3 – 21°C
To reset the max/min thermometer depress the central button (A) and allow the metal floats to decend to the top of the mercury miscus. This might need a mild tap.

Common problems associated with a max/min thermometer

Broken beads of mercury – inaccurate readings. Rejoin mercury by light tapping. Sometimes accompanied with “air” often rendering thermometer broken.	Mercury above the metal floats – arrow 1 This is very difficult to fix and generally the thermometer will be inaccurate and should be replaced. Air bubbles within oil (multiple) – arrow 2 These also tend to indicate a broken thermometer

Breakdown of a maximum/minimum thermometer
Front A Thermometer B Magnet C Backing D

If the max/min thermometer indicates that there is a problem a digital temperature logger can be placed in the area and the records plotted on a graph against time.

The following is an example from a medicine fridge where normal expectations is 2-8°C:

Time