What are Analog to Digital Converter (ADC) Converters?

ADC converters work based on a three-stage conversion process: sampling, quantization, and encoding.

Sampling involves measuring analog signals at specific (or sample) points. The rate of analog to digital signal conversion is referred to as sampling frequency or sample rate. It's important to define at what rate analog signals must be sampled/measured as these signals are continuous in time, while digital systems process information in discrete or binary form consisting of 1s and 0s. Instead of continuously performing the conversion, ADC technology digitizes the continuous signals at specific points.

The next conversion stage or process is quantization. Here, sampled signals are assigned digital values based on their amplitude or voltage level. In other words, continuous digital signals are mapped to discrete voltage levels. Quantization of analog input is subjected to errors such as noise, lots of details, distortion, and clipping errors.

The final conversion process is the encoding stage, where quantized signals are converted into digital representation. This is based on the binary system of 0s and 1s. The result is continuous values converted into a format that can be displayed, stored, and processed for analysis.

There are five main ADC converter types: Flash, Pipeline, Dual Slope, Successive Approximation Register (SAR), and Delta-sigma (ΔΣ). The best analog-digital converter depends on the application. With data acquisition system technologies, only successive approximation registers and delta-sigma are suitable. Other types have their roles but are better suited to non-DAQ applications.

For example, flash ADCs offer extremely high sample rates but have very low amplitude axis resolution, which makes them unfit for data acquisition requirements. Dual-scope offers slow speed and is found mostly in handheld voltmeters. Pipeline ADCs, though they provide a high speed of up to 100 MHz, have higher latency, causing longer delays during signal processing.

Once again, each analog-digital converter has its applications, benefits, and limitations, making choice dependent on measurement requirements.

ADC converter devices and circuits find applications in various processes across different industries. ADC converter applications include:

• Audio processing: Music player systems, including sound cards and audio interfaces, use ADC to turn analog signals into digital formats for processing, compression, and playback.
• Medical field: Medical equipment like ultrasound devices and patient monitors have ADC circuits that enable analysis and diagnosis.
• Electronics: ADC chips help convert analog signals from microphones, cameras, and touchscreens in smartphones, tablets, and laptops into digitally processed and displayed data.
• Automotive systems: Digital ADC circuits are used in, for example, anti-lock braking systems (ABS) and traction control systems in automotive manufacturing.
• Data acquisition systems: ADC circuits form an important part of data logger systems. They enable these DAQ devices to monitor, display, and store physical parameters measured from sensor devices and other data sources.

Many types of ADC Integrated circuit (IC) chips from different manufacturers are available in the market. An example is the AD7982 from Analog Devices. It’s a 6-bit, 100 kSPS ADC found in industrial and medical equipment circuitry. Other ADC chip models are:

• Texas Instruments ADS1115
• Maxim Integrated MAX11254
• STMicroelectronics STM32F4
• Analog Devices AD7766
• NXP Semiconductors LPC11U68

Out of all the five major ADC converter types, the choice of which ADC technology to use is based on application requirements. Pipeline, flash, dual slope, delta-sigma, and successive approximation technologies have been used in devices and equipment requiring analog to digital conversions. The best choice depends on the following considerations:

Requirements: Resolution, sample rate, input range, noise tolerance, power consumption, and type/size are important factors to consider when choosing an ADC package. A compact system would be great for applications where mechanical space may be of concern. KEYENCE NR-500 Series multi-input data logger offers portability and accurate ADC analog to digital conversion for industrial applications.

Converter type: Successive approximation register (SAR) and delta-sigma units suit DAQ applications.

After establishing what factors, such as sampling rate and resolutions, are critical to the application in question, the next item to explore is the existing products or solutions on the market. Manufacturers or sales engineers should be able to provide data sheets and application notes. Compare the features, specifications, prices, and other information on these documents.

For an additional layer of insurance, consulting with an experienced engineer for expert guidance and recommendations may be necessary. Here at KEYENCE, we not only work with seasoned local engineers to help clients choose the right DAQ package but also provide technical guides and data sheets for all our hardware.

Want to know more about our data logger solutions for ADC? Contact us today.