Definition of Digital Instruments
A digital instrument is a device that displays the value of a measured quantity in the form of digital numbers. It operates on the principle of quantization—the process of converting a continuous input signal into a countable output signal.
Digital instruments have a relatively complex structure and are generally more expensive. However, they consume significantly less power compared to analog instruments. Examples include digital multimeters, digital voltmeters, and digital frequency meters.
Key Characteristics of Digital Instruments
Digital instruments exhibit the following important features:
High accuracy in measurements.
Sensitive components that are easily affected by ambient temperature and humidity.
High input impedance, resulting in minimal power draw.
Lower portability.
Higher cost.
Freedom from parallax errors: Unlike analog instruments, which use a pointer to indicate measured values (leading to potential parallax errors), digital instruments display results directly on a screen, reducing such errors.
Construction of Digital Instruments
The structure of a digital instrument is illustrated in the figure below.
Key Components of Digital Instruments
Digital instruments consist of three core components: transducers, signal modifiers, and display devices.
Transducer: Converts non-electrical or physical quantities (e.g., temperature, displacement) into measurable electrical quantities (such as voltage or current). Note that transducers are unnecessary when the input is already electrical.
Signal Modifier: Enhances weak input signals to ensure they can be processed effectively.
Display Device: Presents the measured quantity in numerical form. Light-emitting diodes (LEDs) or liquid crystal displays (LCDs) are commonly used for this purpose.
Advantages of Digital Instruments
Readings are displayed numerically, minimizing human error.
Digital outputs can be directly fed into storage devices (e.g., floppy disks), recorders, or printers.
Lower power consumption compared to analog instruments.
Disadvantages of Digital Instruments
Limited overload capacity.
Temperature sensitivity: Delicate internal components are easily affected by atmospheric conditions (e.g., humidity, dust).
More susceptible to noise interference than analog instruments.
Despite these drawbacks, digital instruments remain widely used in measurement applications.
