ANY-maze Help > I/O devices supported by ANY-maze > Test equipment designed specifically for ANY-maze > The Orofacial pain assessment device (OPAD) cage > OPAD reference information > The OPAD cage temperature controller

The OPAD cage temperature controller

Introduction

The OPAD temperature controller is used to control the temperature of the 'thermal elements' which provide the thermal stimulus to the animal's cheeks when it licks the water bottle spout.

Details of the temperature controller

The temperature controller is in fact two devices, one to control each of the two thermal elements (left side and right side), but they are usually set to the same temperature (unless you've chosen to control their temperatures independently).

Each controller consists of a Peltier device, which actually causes the element to get hot or cold, and a temperature sensor, which provides feedback so the controller knows when the element has reached the programmed temperature.

The controller is able to heat the thermal elements to a maximum of 60°C and cool them to a minimum of 7°C. When heating, the controller can change the temperature at a rate of 0.8°C per second. When cooling the element from a temperature above 25°C, the controller can reduce the temperature at a rate of -0.8°C per second, but when the temperature is below 25°C this rate is reduced to -0.4°C per second.

Within these constraints, the temperature changes are very linear and exhibit very little over- or under-shoot at the ends of a temperature ramp. Note, however, that when reducing the temperature from above 25°C to below 25°C at the maximum rate, the change will have a 'knuckle' in it at 25°C - that's to say that the change will be linear at -0.8°C/s for the part above 25°C, and will then alter to be linear at -0.4°C/s for the part below 25°C; this is by design.

Controlling the temperature during tests

There are two ways in which you can control the temperature of the thermal elements during a test: you can either use an OPAD temperature cycle which allows you to program a sequence of timed temperature changes that should occur during a test, or you can use procedures, which provide more flexibility but which are a little more complicated to set up.

OPAD temperature cycles are described fully here, but essentially they allow you specify a series of temperature changes that you want to occur during a test. The time when each change occurs and the duration of the 'ramp' to a new temperature can be specified. For example, you could set up a cycle in which the temperature starts at 25°C, then after 1 minute ramps up to 50°C over the course of 5 minutes, then remains at 50°C for 2 minutes before ramping back down to 25°C as quickly as possible.

Procedures, which are described here, are more flexible than temperature cycles because the changes in temperature can depend on more things than just the test time. For example, you can specify that temperature changes should occur based on the duration of the animal's contact with the thermal elements, or based on the amount of liquid the animal has consumed, etc.

ANY-maze help topic T1211