Chapter 8 Tutorial

Measurement Fundamentals

Noise Caused by Injected Current Residual capacitances in the instrument’s power transformer cause small currents to flow from the LO terminal of the internal DMM to earth ground. The frequency of the “injected current” is the power line frequency or possibly harmonics of the power line frequency. The injected current is dependent upon the power line configuration and frequency. A simplified circuit is shown below.

HI

DMM

LO

Injected Current

(50 / 60 Hz ac line leakage current)

With Connection A (see below), the injected current flows from the earth connection provided by the circuit to the LO terminal of the internal DMM. This configuration adds no noise to the measurement. However, with Connection B, the injected current flows through the resistor R thus adding noise to the measurement. With Connection B, larger values of R will make the problem worse.

R

HI

VS

 

 

 

DMM

VS

 

 

 

 

LO

R

HI

DMM

LO

Connection A

Connection B

The measurement noise caused by injected current can be significantly reduced by setting the integration time of the internal DMM to 1 PLC or greater (see page 103 for a discussion of integration time).

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Agilent Technologies 34970A manual Connection a Connection B
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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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