Introduction:
Measurement systems are essential in various fields of science and engineering to quantify and evaluate physical quantities. These systems can use either direct or indirect methods to obtain measurements. In present day measurement systems, the use of direct methods is limited, while indirect methods are more commonly used.

Explanation:
1. Direct methods:
Direct methods involve directly measuring the physical quantity of interest using a measuring instrument or device. These methods provide a straightforward and immediate measurement without the need for any additional calculations or assumptions.

2. Limitations of direct methods:
While direct methods are accurate and reliable, they have certain limitations that make them less commonly used in present day measurement systems. Some of these limitations include:

- Invasive measurements: Direct methods often require physical contact or interaction with the object or system being measured. This can be impractical or even impossible in certain situations, especially when dealing with delicate or sensitive objects.

- Disruption of the system: Direct measurements can sometimes disturb or alter the system being measured. For example, inserting a temperature probe into a liquid can cause the temperature to change due to heat transfer. This can introduce errors or inaccuracies in the measurement.

- Limited measuring range: Direct methods are often limited in their ability to measure very large or very small quantities. For example, it may be challenging to directly measure extremely high temperatures or extremely low electrical currents.

- Complexity and cost: Direct measurement techniques may require specialized instruments or equipment, which can be expensive and complex to operate. This can make them less practical for routine measurements or large-scale applications.

3. Indirect methods:
Indirect methods, also known as inferential or indirect measurement techniques, involve inferring the value of a physical quantity based on other measurable parameters or properties. These methods rely on mathematical models, empirical relationships, or calibration curves to estimate the desired measurement.

4. Advantages of indirect methods:
Indirect methods have several advantages over direct methods, which make them more commonly used in present day measurement systems. Some of these advantages include:

- Non-invasive measurements: Indirect methods do not require physical contact with the object or system being measured, making them suitable for non-destructive testing or monitoring.

- Wide measuring range: Indirect methods can often measure a wide range of quantities, including very large or very small values, by using appropriate mathematical models or transformations.

- Cost-effectiveness: Indirect methods can often provide accurate measurements using simpler and less expensive equipment compared to direct methods.

- Flexibility and adaptability: Indirect methods can be easily adapted or modified to measure different physical quantities or conditions by adjusting the mathematical models or calibration curves.

Conclusion:
In present day measurement systems, the use of direct methods is limited due to their inherent limitations, while indirect methods are more commonly used. Indirect methods offer advantages such as non-invasive measurements, wide measuring range, cost-effectiveness, and flexibility, making them suitable for a wide range of applications in various fields of science and engineering.