What Is a Constant Temperature Bath?
A constant temperature bath is a type of apparatus used in scientific experiments.
There are two types of thermostatic chambers: one that changes the air temperature and the other that changes the water temperature (thermostatic tank). The size and specifications vary depending on the application and purpose, ranging from table-top types, large refrigerator-like types, to types in which a single room can be adjusted as a constant temperature bath.
Uses of Constant Temperature Baths
Major types of constant temperature chambers include incubators, constant temperature dryers, constant temperature water baths, and environmental test chambers (cycle testers, constant temperature/humidity chambers, etc.). Incubators are used in scientific experiments to culture microorganisms and cells. In the industrial field, incubators are used to hatch eggs, and in the medical field, incubators are used to maintain the body temperature of low-birth-weight infants. Thermostatic dryers, thermostatic water baths, and environmental test chambers are widely used in biochemistry, organic chemistry, and other fields, and are used for a variety of analytical testing purposes.
Principle of Constant Temperature Baths
A constant temperature bath basically consists of a vessel that maintains temperature, a heating (or cooling) device, a temperature sensor, and a temperature controller. Humidifiers and dehumidifiers are used to control humidity, and fans and agitators are installed to equalize the temperature inside the vessel, depending on the application. The temperature is varied by a heated humidifier, cooler, or dehumidifier, and maintained at the desired temperature by a temperature sensor.
Constant temperature baths are designed primarily to maintain a constant temperature, but depending on the application, the temperature can be programmed to rise and fall repeatedly at regular intervals, or to rise and fall at a constant gradient.
Setting an arbitrary program depends on the plugram device in the constant temperature bath itself and thus on the functionality of the individual product. If the product has a built-in communication interface, it can also be operated remotely using a personal computer. Data can be recorded directly into the constant temperature bath’s internal memory or into an external device, depending on the application.
Structure of a Constant Temperature Bath
Constant temperature baths range in size from 30 cm to several meters on a side, and can be installed in a laboratory.
The general structure of a thermostatic chamber is that it has a door and insulation to prevent temperature changes from the surrounding environment. The inside of the chamber is sealed off from the outside world. In addition, controls are installed to maintain a constant temperature for an extended period of time.
In terms of individual components, constant temperature baths are divided into two types: those that have the entire bath covered by an outer frame and those that do not. In both cases, a case is installed to hold water, and the temperature is controlled at or below the evaporation temperature of the water. In addition, when experiments are conducted at temperatures of 100°C or higher, water cannot maintain the temperature, so some devices use oil to heat the water.
Other thermostatic dryers have timers and temperature increase programs that allow the temperature and temperature increase rate to be set according to the experimental application.
Uses of Constant Temperature Baths
Constant temperature baths are generally used in laboratories, etc., and are often used in water/oil baths and constant temperature dryers.
Thermostatic water/oil baths are mainly used in chemical and biological experiments, where samples are placed in flasks and stirred to maintain a constant temperature.
The usage is simple: fill the tank installed in the instrument with water or oil and set the temperature. However, since experiments are conducted for long periods of time, care must be taken to avoid burns.
Constant temperature dryers and constant temperature-humidity baths are used not only in experiments but also in drying semiconductors, cultivating microorganisms, and drying various instruments.
The usage is simple: open the door, place a sample inside the chamber, set the temperature increase rate, target temperature, holding time, etc., and perform drying and sample observation. In addition to heating, some instruments are equipped with a cooling function that allows them to be used for low-temperature experiments. However, since they may use chlorofluorocarbons or other refrigerants, they need to be outsourced to a specialized contractor.
On the other hand, constant temperature baths using Peltier elements are also available in recent years. Peltier elements can perform cooling and heating by changing the direction of electric current. They are characterized by power savings, CFC-less, small size, and fine temperature control.