Chapter 8 Tutorial

Measurement Fundamentals

Current Measurements

Current measurements are allowed only on the 34901A module.

An ammeter senses the current flowing through its input connections – approximating a short circuit between its input terminals. An ammeter must be connected in series with the circuit or device being measured such that current flows through both the meter and the test circuit.

A resistor, Rs in the diagram below, is connected across the input terminals such that a voltage drop proportional to the input current is generated. The value of Rs is selected as low as possible to minimize the instrument’s burden voltage, or IR drop. This voltage drop is sensed by the internal DMM and scaled to the proper current value to complete the measurement (see the discussion on the following page).

On-Card

S1

Fuse

 

 

 

 

 

 

 

I

RS

LO

+/- Vdc to Input Amplifier and Analog-to-Digital Converter

AC current measurements are very similar to dc current measurements. The output of the current-to-voltage sensor is measured by an ac voltmeter. The input terminals are direct coupled (ac+dc coupled) to the shunt so that the internal DMM maintains dc continuity in the test circuit. Performing ac current measurements demands additional care.

The burden voltage (loading) varies with frequency and input inductance, often causing unexpected behavior in the test circuit (see the discussion on the following page).

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Agilent Technologies 34970A manual Current Measurements, Current measurements are allowed only on the 34901A module
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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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