Incubator- Types, Design, Operation, Handling, Maintenance, Price

An incubator is a type of container, that maintains some specific temperature internally. Generally, the machine operates at an incubating temperature (i.e 37°C). However, you may use it above the incubating temperature as well, based on your necessity. Inside the laboratory, the samples can be the serum for the blood test, chemicals, etc. They are mainly of three types. They are a non-circulating incubator, circulating incubator, and shaking incubator. Here we will be talking about the general operation, applications, handling, and maintenance of the incubator.

Besides that, we will also discuss the contact details of the suppliers for you to purchase the machine in Kathmandu, Nepal.

Types of Incubator

There are various types of incubators available in the market. Some of the types of incubators are stated below.

  • Based on design:- Analog, Digital, and Microprocessor-based
  • Based on application:- Bacteriological (for bacteria culture), Hatchery (for hatching the eggs), Cooling (for both cooling and heating purposes), Agitating (for platelet separation in blood bank), Research (for research purposes), and Baby (for incubating the newborn baby).

Incubator Principle

An incubator helps to maintain a constant temperature within the inner chamber. This is possible with the help of a temperature sensor, temperature controller/ thermostat.

Here I am going to explain to you some basic designs and workings of the non-circulating incubator. But in the market, you may find incubators with many more features than shown in the figure below.

1. Analog Incubator


Construction of incubator
Construction of analog incubator

The incubator connects to an external three-pin power socket. From the power socket, the live wire goes to the thermostat through the fuse and switch.  From the thermostat, the wire then goes to the heating coils. The heating coils surround the inner chamber from three sides. The mains indicator is used to indicate the condition of power from the external supply. Similarly, the heating indicator is used to indicate the condition of the heating coils.

The entire system of fuse, switch, indicator, and thermostat lies inside the incubator surrounded by glass wool.

Glass wool covers all the sides of the incubator. It acts as an insulator for preventing the loss of heat into the surrounding.

You may have an inbuilt L-shaped mercury thermometer to monitor the internal temperature. Besides that, the fan may also be present. The fan is useful for the proper regulation of air temperature within the chamber.


When the machine is given a power supply, the mains indicator will glow. Then the current will go to the thermostat. From the thermostat, the current will flow through the heating coil.

When the temperature of the inner chamber is less than the set value, the thermostat will allow the current to flow through the heating coil. Thus, the temperature of the air will begin to rise up. Once the temperature of the air reaches the set value, the thermostat will cut off. Thus, the current will not flow through the heating coil. Then, the temperature of the air begins to go down. The heating indicator will also stop glowing.

2. Digital Incubator


Construction of incubator
Construction of digital incubator

The design of a digital incubator is similar to that of an analog incubator. The only difference is that instead of a thermostat there is a solid-state relay and the PID temperature controller. Similarly, a temperature sensor is also present.

Besides these, the digital incubator can also have a fan/blower for the proper regulation of the air temperature. If the machine is a cooling incubator or BOD incubator, then you will even find the compressor. The compressor allows for the cooling of the inner chamber of the machine.


The working mechanism is almost similar to that of the analog incubator. Here, the PID controller and the solid-state relay (SSR) acts as a controller for the heating coils. When the temperature of the inner chamber of the incubator is lower than that of the set value, the controller will supply a certain DC voltage to the relay. Then the relay will get activated causing the flow of AC current to the heating coils. Thus the coil begins to heat up the air.

When the actual temperature of the air goes closer to the set value, the PID controller will activate and deactivate the relay continuously. Thus the heating coils will go ON/OFF continuously. So, by controlling the duration of the ON and OFF stage, the incubator helps to maintain an almost accurate result with not more than 1°C of variation.

The resistance temperature detector (RTD) such as the PT100 sensor, senses the temperature of the air. Then, it converts the temperature to the resistance value and supply to the controller. The controller will compare this incoming signal with the set value.

Analog Vs Digital Incubator

An analog incubator is the simplest type of incubator. It is cheap and easy to operate. But, there are few problems with it. The first problem is that the accuracy of the analog incubator is less than that of the digital incubator. Besides that, there is no display board. So, you will not be able to see the actual temperature of the internal chamber.

A digital incubator is an advanced version of an incubator. It is quite expensive. However, it is easy to operate. It has got a better accuracy. Similarly, the display board present in it allows the user to see the actual temperature of the internal chamber.

Incubator Temperature Range

Theoretically speaking, the temperature range of the incubator is from room temperature to 100°C or less than that. 

Since the normal bacteriological incubator does not have a cooling system, it can not maintain the temperature below room temperature. Similarly, the incubating temperature is the body temperature (37°C). So, the incubator is designed to operate at body temperature. Thus, the temperature of the machine does not go too high. For example, the upper limit of temperature for the bacteriological incubator of the Osworld Company is just 60°C. Based on different companies and models this value can slightly differ.

I have faced a problem while setting the lower value of the bacteriological incubator. Some companies tell you that the lower limit is the room temperature. Some other say that the lower temperature is 5°C above the room temperature. But, I have seen that the machine is not able to maintain 30°C when the room temperature is just 25°C. Thus in conclusion, if you are planning to operate the machine at a temperature below 37°C, then I suggest you consult the supplier/manufacturer before purchasing it.

There is another kind of incubator which is known as the BOD incubator. This kind of incubator has got a compressor for the cooling action. Thus this machine can both incubate or cool the internal chamber.

How to use an incubator?

(Incubator procedure)

  • First of all, connect the power cable.
  • Then, turn on the machine.  The digital incubator will show the display of the present value (PV) and the set value (SV). If needed,  set the set value (SV).

If an incubator is analog, just turn the knob of the thermostat to the required set value.

  • Allow the temperature of the internal chamber to reach the set value.
  • Put the sample inside the incubator when the temperature reaches the set value.

(Note:- When you put the sample inside the machine depends on the type of sample and task you are performing. Some samples such as reagents from the biochemistry lab need to be incubated for a set period of time. In this case, the temperature inside the machine should reach the set value, before you put the reagent. On the other hand, the samples may need to be stored for an undefined period of time. In such a case, you may even place the sample inside the incubator before turning on the machine. )

Handling of Incubator

  • Put the machine on a stable and solid surface.
  • Put the machine in an open space. In other words, there should be sufficient space for the air to circulate around the machine from all sides. So, it will be better, if the machine is placed at least 2 feet away from the wall and other equipment.
  • If you think that the incubator is not working properly, then take another mercury thermometer and measure the temperature of the incubator. Then compare that value with the preset value of the display.

Maintenance of Incubator

The methods that I will be explaining in this topic will be for the experts. General customers are strictly prohibited to carry on these things.

An incubator can undergo a number of problems. In such a case, you may even need to open the machine. Since the machine consists of glass wool from all sides, you need to wear nitrile gloves, a face mask, shoe cover, and glass for safety purposes. Else you may have skin irritation, allergies, rashes, etc.

 Here I will be discussing some of the problems and the methods to deal with them.

1. No power supply?

If the machine does not get any power supply, you will not see a display in the PID temperature controller. Similarly, the indicator of the mains switch and the heater coil indicator does not light up.


The problem can be due to fluctuation in the power supply. The problem can also be due to the loose connection of the power cable. Besides that, the power cable, indicators, fuse, or switch may have been damaged. In such a case, you will have to replace the damaged piece with a new one.

2. Heating coil does not work?

If the coil does not work, then the temperature of the air will not rise up.


If the heating coil is burned/damaged, the connection between the three coils will be broken. In such a case, the machine will have an open circuit. Hence, the current will not flow through the coils. In such a case, you need to check for all the connections among the coils. While connecting the detached coils, make sure that the coils do not make any physical contact with the internal or the external surface of the machine. You may even use black tape if needed.

The solid-state relay (SSR) supplies current to the coil. In other words, it acts as a switch for the switching of the coil. You can also check the condition of the SSR, which I have stated in the topic of SSR.  Make sure to check the LED present in the relay.

3. Chamber does not heat properly?

Sometimes, the inner chamber will heat, but the temperature will not reach the set value.


If the door of the machine is not closed properly, or if the gasket covering the door has been broken, there can be a high chance of the leakage of air from the inner chamber to the environment. The loss of air leads to the loss of heat. Thus the temperature will not rise up.

The temperature sensor (Pt 100 sensor) may not work problem. In that case, you need to check it. There are a number of ways to check the condition of the temperature sensor, which I have stated in the topic of the Pt100 sensor.

The problem can also be in the PID controller.

4. Error in the Present Value (PV)?

The present value shown by the PID controller may not be the same as that of the actual temperature measured by the mercury thermometer.


The problem can be due to the poor connection of the temperature sensor to the PID controller. In such a case, remove the wires of the sensor from the controller. Then reconnect it. If the sensor is defective then replace it with a new one.

The problem can also be with the PID controller.

5. Error with PID controller?

PID temperature controller is the brain for the digital incubator. So, if the PID controller becomes defective, then the machine can undergo a number of problems. Some of them are as follows.

  • The solid-state relay may not activate.
  • The inner chamber may not heat. Even if it heats, the temperature may not reach the set value.
  • The display may show a faulty reading of the present value.
  • Since the display is embedded in the PID controller, a defective controller may not display any value.


There are few ways to deal with the problem of the controller. The step you can do is, to do the auto-tuning of the controller. Auto-tuning is a kind of internal calibration to calibrate the temperature. If you are trying to do auto-tuning, then close the door of the machine properly. Do not put any samples during auto-tuning. Set the value to 37°C. Then press the button of the auto-tuning. Then the process of auto-tuning will begin. During that time, the display will keep on blinking. This process can take about half an hour or more, based on the size and power of the incubator. Once the tuning is over, the display will stop blinking.

Another problem can be due to the error in the programming of the controller. So to correct the programming you need to know the values of the parameters shown in the display. Since the programming depends upon different models of different manufacturers, I can not tell you the values. However, you can see the model of your controller. Then, search for the manual on the internet. You may even find the information on Youtube. Then look for the errors in the programming and the process of auto-tuning.

6. Problem with Thermostat?

If the incubator is an analog type, then there will not be any PID controller. Instead of that, there might be a thermostat. For more details about the working and the testing of the thermostat go through my post related to it.

Supplier of the incubator in Nepal

There are many suppliers that deliver incubators in Kathmandu, Nepal. Some of them include Menaka Enterprises Pvt. Ltd., Sunrise Surgical House, Eden Technology, etc. Eden Technology is located in Tinkune, Kathmandu. It is an authorized dealer of Osworld products. So, you can contact the supplier to know the price and purchase the machine.



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