Chapter 8 Tutorial

Measurement Fundamentals

AC Voltage Measurements

The main purpose of an ac “front end” is to change an ac voltage input into a dc voltage which can be measured by the ADC.

Signal Conditioning for AC Measurements Input signal conditioning for ac voltage measurements includes both attenuation and amplification. An input coupling capacitor (C) blocks the dc portion of the input signal so that only the ac component is measured. Ranging is accomplished by combining signal attenuation from the first-stage amplifier and gain from the second-stage amplifier.

X 0.01

X1

C 1 MΩ

HI A1

LO

A2

 

 

 

 

 

AC to DC

 

 

 

 

 

 

 

 

 

 

Converter

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

X1

X10

X100

The first stage implements a high input impedance (1 MΩ ) switchable compensated attenuator. The second stage provides variable-gain signal amplification to scale the input to the ac converter to the full-scale level. Any residual dc offset from the attenuator and amplifier stages is blocked by a capacitor.

An ac voltage front end similar to the one discussed above is also used

to measure ac current. Shunt resistors convert the ac current into an 8 ac voltage which can then be measured. Current shunts are switched to provide selectable ac current ranges.

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Agilent Technologies 34970A manual AC Voltage Measurements
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34970A specifications

Agilent Technologies 34970A is a versatile data acquisition and measurement system that has gained popularity in various industries, including research and development, manufacturing, and education. The primary purpose of the 34970A is to offer an efficient solution for data collection, monitoring, and analysis, which can significantly enhance productivity and accuracy in testing applications.

One of the main features of the 34970A is its modular design, allowing users to customize the system according to their specific measurement needs. The mainframe can accommodate up to three plug-in measurement modules, which can include various types of measurements such as analog, digital, temperature, and frequency. This modularity provides flexibility for users to tailor the system to their requirements, making it highly adaptable to different applications.

Another notable characteristic of the Agilent 34970A is its impressive channel configuration. The system can support up to 120 measurement channels when fully configured, enabling extensive data acquisition without the need for multiple devices. This capability is essential for applications requiring simultaneous monitoring of multiple parameters or locations.

The 34970A utilizes advanced signal processing technologies to ensure high-accuracy measurements. The internal 6.5-digit resolution multimeter provides precise readings, while the device also supports various input types, such as thermocouples and RTDs for temperature measurements. The ability to perform mathematical functions, such as summation and averaging, on the acquired data further enhances its usability.

For data storage and management, the Agilent 34970A features built-in memory for storing up to 20,000 readings. Users can also easily transfer data to a PC through the RS-232 interface or GPIB (IEEE 488) for further analysis and reporting. Additionally, it offers the capability to program automatic data logging and scheduling of measurements, which streamlines the testing process and reduces manual intervention.

In terms of user interface, the 34970A is equipped with a large graphical display that provides clear visualization of measurement data and easy navigation through settings and options. The menu-driven interface makes it accessible for users of all skill levels, simplifying the setup and operation of the device.

Overall, the Agilent Technologies 34970A stands out for its modularity, high channel capacity, advanced measurement technologies, and user-friendly interface. As a reliable and efficient data acquisition system, it is well-suited for a wide range of applications, making it an essential tool for engineers and technicians looking to enhance measurement precision and efficiency.
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