+ Submit your article here

What are Thermo-hygrographs?

7/31/2012 4:56:35 PM | by Anonymous


Usually configured with a pen which records data of temperature and humidity on a revolving cylinder that has a graph on it; thermo-hygrographs are also known as chart recorders. Devices that record data only for atmospheric temperature are known as thermographs and devices that only record humidity or dew point of the atmosphere are known as hygrographs. Since thermo-hygrographs are able to record both data, thus their name which is a combination of thermograph and hygrograph. These devices usually have a circular revolving cylinder placed adjacent to the vital components to note the changing humidity and temperature. These vital components have an extension lever that holds the pens on top of the graph to record the changes. As for the temperature recording, the pen at the end of the lever is controlled by the changes in the bi-metal sensitive metal strip which bends as the temperature changes. As the pen moves over the graph, the changes get recorded for later referencing.


As for humidity, the elements which are used to detect the humidity of the surrounding atmosphere is usually made out of several strands of specially treated human hair that lengthen and shorten with the changes in humidity. Similarly to the temperature arm, the humidity element is also connected to the pen through a linkage arm and as the pen moves, the changes in humidity are recorded as an ink line on the chart. The linkages connecting the pens for both temperature and humidity are designed in a away to give linear movement for the recordings to ensure that the results are as accurate as possible.


The graphs are produced to have a continuous variation of atmospheric temperature and humidity in relation to time. The relative temperature and humidity of the atmosphere recorded on the same graph and to differentiate between these two, a red pen is used to record data of temperature and a black pen is used to record data of humidity. The pens that are used in these instruments are usually fiber tipped that contain sufficient ink to take records continuously for 9 months. The pens can also be replaced once the ink starts to fade. As both the pens would be recording data at the same time, there is a possibility that the pens could collide if the temperature was to go too low or the humidity levels were to go too high. To prevent this, the length of the humidity arm which holds the black pen is usually shorter as compared to the longer temperature arm. Because of this, the traces would be displaced in time with respect to one another.


The role of these instruments is vital in many industries that need to be aware of the temperatures and humidity conditions of the environment. Temperature and humidity can affect manufacturing processes, storage of some different types of materials, the weight of different types of materials such as wool, paper, tobacco or confectionery and also play an important factor in human comfort. For example, the temperature and humidity conditions need to be recorded in concert halls to ensure that they are within human comfort zones. In museums thermo-hygrographs record data for organizers to inform them of the conditions in the museum and they can then deduce from these records what type of materials can be kept in the museum as certain old materials may deteriorate in certain conditions. The organizers of the museum then make arrangements accordingly to house different types of artifacts.


Some thermo-hygrographs may even come with added features such as an alarm function which would inform the user in case of abnormal humidity or temperature. This could act as a safety feature to prevent any accidents from occurring. Other added features can be digital display and sensor extension.

Are you sourcing for a product or service?

Do you need a quotation?