Chapter 7 Measurement Tutorial

Resistance Measurements

Resistance Measurements

The Agilent 34401A offers two methods for measuring resistance:

2-wireand 4-wireohms. For both methods, the test current flows from the input HI terminal and then through the resistor being measured. For 2-wire ohms, the voltage drop across the resistor being measured is sensed internal to the multimeter. Therefore, test lead resistance is also measured. For 4-wire ohms, separate “sense” connections are required. Since no current flows in the sense leads, the resistance in these leads does not give a measurement error.

The errors mentioned earlier in this chapter for dc voltage measurements also apply to resistance measurements. Additional error sources unique to resistance measurements are discussed on the following pages.

4-Wire Ohms Measurements

The 4-wire ohms method provides the most accurate way to measure small resistances. Test lead resistances and contact resistances are automatically reduced using this method. Four-wire ohms is often used in automated test applications where long cable lengths, numerous connections, or switches exist between the multimeter and the device- under-test. The recommended connections for 4-wire ohms measurements are shown below. See also “To Measure Resistance,”

on page 17.

 

 

HI

 

 

HI-Sense

R =

Vmeter

Ideal

Itest

Meter

I test

LO-Sense

7

 

LO

203

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Image 209
Agilent Technologies 34401A manual Resistance Measurements, Wire Ohms Measurements

34401A specifications

Agilent Technologies 34401A is a highly reputable digital multimeter (DMM), renowned for its accuracy, versatility, and performance in a wide range of measurement applications. First introduced in the early 1990s, the 34401A has become a staple in laboratories, manufacturing environments, and educational institutions due to its robust build and comprehensive features.

One of the standout characteristics of the 34401A is its impressive accuracy, boasting a basic DC voltage accuracy of 0.0035%, making it ideal for precise measurements in electronic testing. The multimeter offers a wide range of measurement capabilities, including voltage (DC and AC), current (DC and AC), resistance, frequency, and continuity test, making it a highly versatile tool for engineers and technicians.

The 34401A utilizes a 6½-digit resolution, enabling the user to measure small changes in electrical signals with remarkable precision. With a sampling rate of up to 1000 readings per second, it can handle dynamic test requirements, providing timely results without sacrificing measurement integrity.

In terms of connectivity, the Agilent 34401A includes a GPIB (General Purpose Interface Bus) for remote operation, allowing users to automate their testing processes and integrate the multimeter easily into larger measurement systems. This feature is particularly beneficial in automated test environments, where speed and accuracy are paramount.

Additionally, the DMM incorporates advanced measurement functions, such as statistical analysis, including mean, standard deviation, and minimum/maximum readings, which provide users with valuable insights into their data. The instrument's user-friendly interface, complete with a clear digital display and intuitive controls, enhances usability and ensures that users can easily navigate its various functions.

Robust software support further extends the capabilities of the Agilent 34401A. It is compatible with a range of software tools for data logging and analysis, enabling users to efficiently document and analyze their measurements over time.

In summary, Agilent Technologies 34401A stands out in the realm of digital multimeters due to its high accuracy, extensive measurement functionalities, and user-friendly features. Whether for research and development, quality control, or educational purposes, the 34401A remains a preferred choice for professionals demanding reliable and precise measurement solutions. Its enduring legacy in the industry speaks to its performance and reliability, making it an essential tool for anyone involved in electronic testing and measurement.