Mechanical Comparator :All You Need to Know
The reed type mechanical comparator is a precision instrument used to compare the dimensions of a workpiece with standard dimensions. As its name suggests, the reed type comparator belongs to the category of mechanical comparators. Other comparators such as the sigma comparator, Johansson mikrokator, etc., also fall under this category.
In a reed type mechanical comparator, the external appearance may resemble that of other mechanical comparators. However, its internal construction and working principle are relatively simple compared to other types of comparators.
Now, let’s explore the construction, working principle, applications, advantages, and disadvantages of the reed type mechanical comparator.
The construction of this mechanical comparator is straightforward, consisting of five major parts as detailed below in the reed type mechanical comparator.
Plunger (Spindle): The plunger is a small metal component that acts as a sensing probe in the mechanical comparator. It detects dimensional variations in the workpiece.
Blocks: There are two blocks in the comparator—a fixed block and a movable block. The movable block is connected to the plunger at its bottom and both blocks are typically made of metal.
Reeds: The comparator contains two pairs of reeds. One pair is positioned horizontally, bridging the fixed and movable blocks in the center. The other pair is placed vertically, connecting the upper ends of the movable and fixed blocks.
Needle or Pointer: The pointer is located at the junction of the vertical reeds. It is typically made of lightweight materials such as plastic, aluminum, or acrylic.
Scale: A graduated scale provides output readings based on the pointer’s deflection. Measurement values are marked on a graduated plate within the comparator housing, which is enclosed by fiberglass.
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Working principle of reed type mechanical comparator
Now let’s see its working principle and how it is operated?
The read type mechanical comparator consists of a spindle, blocks, reeds, needle and a graduated scale. Initially, with the help of slip gauges or gauge blocks, the whole comparator is calibrated to zero scale. Then the work to be measured or analysed is kept under the plunger contact point. If there is any dimensional variation compared to standard dimensions (slip gauges), the movement of the plunger or spindle will be in an upward or downward direction.
The movable block also moves since it is attached to the plunger. Simultaneously the vertical reed fixed to the movable block also moves upward. The fixed parameter and linear motion of the movable parameter make the needle or pointer deflect. The deviation in the dimension of the workplace may result either in positive or negative value.
Magnification of reed type mechanical comparator
The deflection of the pointer or needle is directly proportional to the displacement of the movable or floating block. Therefore the large angular movement or displacement of the needle is produced by the small displacement of the plunger.
The magnification of the reed type comparator is actually less than 100. If any optical lens system has been used then the magnification is multiplied as per the lens system.
The magnification range of Reed type mechanical comparator is from 500 to 1000. The sensitivity of the reed type comparator is mm/scale division.
Advantages of reed type mechanical comparator
Advantages of reed type mechanical comparator
- Reed type comparator has only fewer components.
- It is a frictionless device due to a very less number of internal components.
- It is very lightweight and portable.
- It is very cheap and easy to use.
- It is highly sensitive.
Disadvantages of reed type mechanical comparator
- Decrease in activity of any movable parameter inside the comparator can result in poor accuracy of the instrument.
- Since it is very sensitive, it is not suitable for any vibration conditions.
- The range of the measuring scale in this comparator is limited.
Applications of reed type mechanical comparator
- It is used to measure the dimensional deviation of the workpiece with the standard dimensions.
- It is used in mass production and testing laboratories for analysis purpose.
