Introducing a Diverse Range of Ovens!

Types and Methods of Ovens

Ovens can be broadly classified into the following four types.

1. Natural convection oven (Natural convection)

Since the heat from the heater creates gentle convection within the chamber, it is suitable for drying samples such as powders and granules that should not be scattered.
<Example: NDO-420 / NDO-520 Series>

The heater is installed beneath the bottom plate. It generates heat regulated according to the set temperature. The heated air rises and circulates through the perforated metal (punching holes) in the bottom plate, warming the entire chamber. A temperature sensor mounted at the top of the chamber measures the internal temperature and provides feedback to the temperature controller.

2. Forced air flow oven (Forced air flow)

The internal fan forcibly circulates air throughout the chamber, resulting in less temperature fluctuation compared to natural convection models and significantly reducing drying time.
<Example: WFO-420 / NDO-520 Series>

The basic structure is the same as that of natural convection ovens. A fan is installed at the heater section to create forced air convection. Air is circulated not only from top to bottom but also horizontally from the rear, which minimizes temperature fluctuations.

3-1. Drying oven (Natural convection)

Natural convection method that performs drying at relatively low temperatures of 80°C or below.
<Example: AWO-1001>

The basic structure is identical to that of natural convection ovens. Heated air rises and circulates through the perforated plate (Punching holes) in the bottom plate to warm the entire chamber. Any water droplets are collected in the receiving vat (water tray) located at the bottom.

3-2. Drying oven (Dehumidification and drying)

A dehumidifying drying method that does not use a heater, gently drying equipment.
<Example: LWO Series>

Dehumidification and drying are performed by a refrigeration unit without the use of a heater. Moisture from the equipment is cooled and condensed by the “condenser” at the rear, then drained through the drain on the side of the unit. Dry air is blown out from the bottom of the chamber to accelerate the drying of the equipment. This allows for the drying of heat-sensitive equipment and samples.

4-1. Vacuum drying oven (Vacuum + chamber heating)

Drying under vacuum or in an inert gas atmosphere.
Suitable for samples that are difficult to dry with conventional ovens or are sensitive to oxidation.
<Example: VOS-210C · 310C / VOS-452SD · 602SD>

Drying under vacuum or in a gas atmosphere. Heaters are installed within the chamber walls on both sides. Samples are heated through radiation from the inner walls and thermal conduction from the shelf boards.

4-2. Vacuum drying oven (Vacuum + chamber heating + heated shelf)

<Example: PVO-450>

A unique shelf-heating system utilizing shelves. The shelves are heated by warm air without the use of heaters or oil, allowing easy removal of shelf boards and eliminating concerns such as overheating or liquid leakage.

4-3. Vacuum drying oven (Vacuum + hot plate)

<Example: VOM-1000A · A1 · B>

Drying under vacuum or in a gas atmosphere. Designed for micro-samples, it uses a hot plate for heating. The chamber is made of glass, allowing for easy observation of the samples.

Main Applications

Various Safety Features

Given that these units are frequently operated at high temperatures, they are equipped with a range of safety features.

Door Open Alarm

An alarm is displayed and control is stopped (Heater OFF, Circulation Fan OFF) when the door is open or ajar. (In Models NDO and WFO series, a buzzer sounds if the door remains open for one minute.) This prevents abnormal overheating of samples caused by continuous heating while the door is left open. In Model WFO model, the fan stops to prevent the blast of hot air from escaping.

Sensor Failure / Heater Disconnection Alarm

An alarm is displayed if a temperature sensor disconnection (open circuit), short circuit, or heater burnout occurs.

Upper and Lower Temperature Limit Alarm

An alarm is displayed if the temperature exceeds the set upper or lower limits. Depending on the model, two-stage settings are available, and there are two types of responses: continued control or controlled shutdown, depending on the specific alarm type.

Variable Independent Overheat Protector

The power is forcibly shut OFF if the internal temperature rises above the temperature set on the “Overheat Protector.” The setting of the overheat protector is adjustable and should be set 20 to 30°C higher than the target internal temperature.

Earth Leakage · Overcurrent Breaker

The breaker trips and cuts OFF the power if a ground fault (leakage) occurs or if an overcurrent flows through the circuit.

Temperature Distribution Accuracy

The smaller the temperature variance within the chamber, the more uniform the temperature control. This variance is referred to as “Temperature Distribution Accuracy.”

Temperature Distribution Accuracy

1. Temperature sensors are installed at nine points (①–⑨), including the center and positions located at one-tenth of the distance from each inner wall of the chamber.
2. Temperature data is collected once the internal chamber temperature has stabilized.
3. The collected data is recorded in accordance with the standard notation (JTM K07 (2007)).

Internal Chamber Sensor Positions

In the case above, with a set temperature of 100°C, the chamber center is 101°C, the maximum point is 108°C, and the minimum point is 96°C. Consequently, the spatial temperature variation is 7°C, and the temperature gradient is 12°C.
(Note: Both are calculated using the average values of each point.)

Convenient Features for Enhanced Operability

Options

Types of Shelves

There are two main types of shelve boards used in the ovens.

1. Perforated Metal Type (Punching holes)		A type featuring numerous round punched holes in a stainless steel (SUS) plate. Convenient for holding items with narrow bases, such as test tube racks, or slender vessels. Compared to the wire type, it may slightly restrict airflow.
2. Wire Type		This type consists of stainless steel (SUS) wires assembled in a grid pattern and welded together. It offers minimal resistance to airflow, making it advantageous for reducing temperature variance. However, slender instruments or test tube racks with thin bases tend to be unstable on this surface.

Base Stand

VOS-602SD with Model HSS Base Stand

Stacking Stand

Shelf boards and Shelf Support Brackets

Exhaust Unit

Vacuum Pump

Cold Trap