Temperature: How To Measure And Control

One of the most important concepts in reptile keeping – and one of the most misunderstood – is temperature control. -+

All pet reptiles are completely reliant upon us to provide them with the environmental temperatures they need to control their own body temperatures. As reptiles cannot regulate their body temperature internally as we do, they need to be able to move between warm and cool areas to enable their bodies to function normally.

There are many ways to produce heat in the confines of an enclosure – which we’ll cover in a separate article – but what we are concerned with here are the most efficient and effective ways of monitoring and controlling it. First of all, there are two terms that are often mixed up: thermometer and thermostat.

A Thermometer is a piece of equipment that is used to measure temperature. These can be digital or analog, and must be used properly to maintain accuracy. They read temperature, they do not control it.

A Thermostat controls temperature. It does this by using a sensor to read the temperature inside the enclosure then regulating the power being sent to the heating equipment (mat, bulb, ceramic etc).

Both are vital to making sure that your temperatures remain where they should be for your pet.

There are two scales that record temperature, celsius (ºC) and fahrenheit (ºF). It doesn’t matter which one you use, although fahrenheit is the more traditional reading and still mostly used in the United States, as long as you choose one and stick to it. We use centigrade here, as it is a little simpler.

Let’s start with measurement.

What is the best way to measure temperature in your enclosure?

Always use a digital thermometer. The dial type of analog thermometers are notoriously inaccurate, and due to their design react very slowly to changes in air temperature as they are usually adhered to the wall of the vivarium. Self adhesive liquid crystal thermometers can work, but their placement is absolutely critical and they can be very hard to read.

Infrared thermometers can be incredibly accurate, but it’s worth bearing in mind that they need to be held at the correct distance from the surface being measured – they are calibrated for different distances – and they read surface, not air temperature. This can be very useful when measuring basking spot temperature or substrate in an incubator, but can be misleading when you want ambient air temperature in the vivarium.

The most effective piece of equipment is a good quality digital thermometer with a maximum/minimum function. This will not only tell you the current air temperature in the area where the probe is placed, but at the touch of a button you can check the minimum and maximum temperatures read in that area (provided the probe hasn’t been moved, of course). This is especially useful when checking on nighttime temperatures, or looking to see if midday temperatures are rising too high.

Sometimes confusion arises over where the probe should be placed. We want to be reading the temperatures in the places where our reptile will be spending time; it’s no good reading the temperature near the roof if your reptile lives on the ground, or on the ground if it lives higher up in branches. So, to read the warm end for a bearded dragon would need the probe to be placed on or just above the substrate outside of the hottest area (directly under the bulb). The basking temperature would be taken by placing – or attaching – the probe directly under the heat bulb in the place where the dragon will sit. Don’t worry, your pet won’t chew on the cables like a mammal would!

The temperatures that you need to know are:

Basking area/hot spot
Warm end daytime
Cool end daytime
Warm end nighttime
Cool end nighttime

What type of thermostat do I need?

A lot will depend on the design of your enclosure, the ventilation, how it’s heated, what temperature the room outside is – there are an enormous number of factors that can affect your pet’s temperatures! Your best way of controlling temperatures is with a thermostat. These come in several different types, which all work in slightly different ways:

Mat stat or Ministats – simple on/off stats. The simplest form of thermostat, these are a basic on/off switch that should be used with heat mats and heat cables only. When the probe senses that the set temperature has been reached, it cuts power to the heat mat until the temperature at the probe dips below the set temperature, at which point it supplies power to the mat again.

Dimming thermostat. These are for use with heat lamps that give out visible light, although they can be used with deep heat projectors and ceramic heaters. They act like a domestic dimmer switch, so that when the temperature reaches its set point the bulb is dimmed gradually to reduce the temperature without a sudden switch off. It’s more natural for your animal, and your bulbs will last longer.

Pulse proportional thermostat. Incredibly accurate, these should only be used with heat sources that do not give out visible light. They work by sending pulses of electricity to the heating element, reducing the pulses when the probe is above the set temperature, and increasing them when the probe is below the set temperature. When used with a heat cable in an insulated box they make very accurate incubators. Never use a pulse stat with a light bulb, as it will flash – this is not pleasant for your pet, and blows bulbs very quickly.

Make sure that your thermostat is rated for the wattage of your heat source, this information should be printed on the outside of the box.

Thermostats save lives. On the rare occasions that we have a heat wave it can be the difference between life and death to have automatic control on your heating equipment!

At a glance:

Mini Stats should be used for heat mats and heat cables.

Dimming stats should be used for basking lights and deep heat projectors.

Pulse stats should be used for ceramic heaters.

There are several ranges of thermostats that are controlled by a touch screen, and are programmable. These are excellent for providing a temperature drop at night, which is appreciated by almost all reptiles, and some of them even control more than one heat source.

However complex the unit you use, the basic principles are the same. Temperatures are controlled by your thermostat, and should always be checked with a good digital thermometer. If you are unsure of anything, please ask – we’re here to help!

Temperature: How To Measure And Control