What is a voltage sample device?How does it differ from a data acquisition system?

Simply Put: A voltage sample device is a core component of a data acquisition system.

1. Introduction to voltage sample devices

A voltage sample device is a device specifically designed for measuring voltage signals. In practical applications, voltage measurement generally falls into two categories:

a. measuring voltage signals output by sensors, and

b. measuring circuit voltages such as power supply rails. 

The voltage sample device discussed in this article belongs to the first category. It is a standalone device dedicated to sensor voltage measurement. Internally, it integrates signal conditioning circuits and an analog-to-digital converter (ADC), enabling direct conversion of analog voltage signals from sensors or circuits into digital data. With a focused function and high efficiency, voltage sample devices are a direct and practical choice for voltage measurement applications. They typically feature multiple input channels, allowing synchronous acquisition of voltage signals from multiple sensors.

2. Input Range Selection for voltage sample devices

In most cases, voltage sample devices support an input range of ±10 V. This is mainly for two reasons:

First, the majority of sensors output analog voltage signals that are intentionally designed within standardized ranges, such as 0–5 V, ±5 V, or ±10 V. These ranges have effectively become industry standards for analog signal transmission. Designing acquisition instruments to match these ranges ensures optimal measurement accuracy without resolution loss.

Second, from a circuit design perspective, this voltage range allows operational amplifiers and ADCs to achieve the best balance among accuracy, sampling speed, and power consumption.

3. Sensors and ADC

Most physical quantities we aim to measure—such as temperature, pressure, speed, displacement, sound, light, and vibration—vary continuously in nature and are therefore analog signals. Sensors convert these physical quantities into continuously varying electrical signals, typically voltage or current, which are also analog in nature. For example, when a temperature sensor detects a gradual increase from 20℃to 21℃, its output voltage may change continuously from 1.000 V to 1.050 V, with infinitely many voltage values in between, corresponding to infinitely many temperature points.

However, the internal operations, storage, and transmission of data in modern information processing cores such as computers, microprocessors (single-chip microcomputers), and digital signal processors (DSP) are all discrete 0 and 1 digital signals, which cannot directly process continuous analog signals. Therefore, analog-to-digital converters (ADC) are needed.

4. Working Principle of a voltage sample device

Multiple input channels receive analog voltage signals from external sensors. These signals are then processed by conditioning circuits, including electrical isolation protection, programmable amplification, and anti-aliasing filtering, to ensure signal quality during sampling.

The conditioned signals are then converted into digital data by the ADC, enabling efficient processing and analysis. Finally, the digitized data is transmitted via communication interfaces to a host computer or control system for storage, visualization, and further analysis.

5. Introduction to Data Acquisition Systems (DAQ)

Compared with a voltage sample device, a data acquisition system (DAQ) represents a broader and more comprehensive concept. In addition to voltage measurement, a DAQ system can directly process signals from various sensors—such as temperature, pressure, strain, acceleration, and humidity—by using dedicated signal conditioning modules or cards. A DAQ system can therefore be viewed as an integrated solution designed for complex measurement tasks involving multiple signal types and large channel counts.

6. Relationship Between voltage sample devices and DAQ Systems

Sensor outputs are often weak, typically at the millivolt level, and are highly susceptible to noise. Such signals are not suitable for direct acquisition. At the same time, voltage sample devices usually operate within a ±10 V input range and cannot directly accept these low-level signals. This is where front-end signal conditioning becomes essential. Signal conditioning modules perform amplification, filtering, isolation, and other preprocessing functions, converting weak and noisy sensor outputs into standardized voltage signals suitable for acquisition. This distinction represents a fundamental difference between a DAQ system and a standalone voltage sample device.

Because different sensor types produce signals with widely varying characteristics, each requires specific preprocessing before connection to a voltage sample device. For example, thermocouples generate extremely low-level, nonlinear millivolt signals. Accurate measurement requires high-gain, low-noise amplification, cold junction compensation, and open-circuit detection at the circuit design level. This is why strain, temperature, and other specialized modules in commercial DAQ systems are primarily designed to perform unique signal conditioning tasks. Their role is to convert raw sensor outputs into standardized voltage signals, which are then digitized by the voltage sample device. In this sense, the voltage sample device is the fundamental building block of any data acquisition system.

7. Software Display and Data Analysis

Once voltage signals are acquired, they can be scaled, converted, and displayed using host software. Based on the characteristics of the acquisition hardware, raw digital data is first converted back into voltage values. Then, using sensor-specific parameters and, where applicable, cold junction temperature data, the software performs engineering unit conversion to output readable and meaningful physical quantities. At this stage, the complete data acquisition workflow is accomplished.

8. Choosing Between a voltage sample devices and a DAQ System

A voltage sample device can be regarded as a focused, plug-and-play DAQ solution designed specifically for voltage measurement. In contrast, a full DAQ system offers greater scalability, higher channel density, and the ability to handle mixed sensor types within a single platform.

The choice between the two should always be based on specific measurement objectives and application requirements. In recent years, a number of specialized data acquisition manufacturers have emerged in China. Among them, KETU&TEST stands out with its KTVS-32A voltage sample device, which demonstrates strong expertise in the accurate digitization of voltage signals from a wide range of sensors.

Furthermore, KETU&TEST not only has in-depth research in voltage acquisition, but will also expand into more advanced and integrated complete data acquisition systems in the future, committed to providing integrated solutions from precise sensing to intelligent analysis, and promoting the intelligent upgrading of industries.