Rejecting Power-Line Noise Voltages

Chapter 7 Measurement Tutorial

A desirable characteristic of integrating analog-to-digital (A/D) converters is their ability to reject spurious signals. Integrating techniques reject power-line related noise present with dc signals on the input. This is called normal mode rejection or NMR. Normal mode noise rejection is achieved when the multimeter measures the average of the input by “integrating” it over a fixed period. If you set the integration time to a whole number of power line cycles (PLCs) of the spurious input, these errors (and their harmonics) will average out to approximately zero.

The Agilent 34401A provides three A/D integration times to reject power-line frequency noise (and power-line frequency harmonics). When you apply power to the multimeter, it measures the power-line frequency (50 Hz or 60 Hz), and then determines the proper integration time. The table below shows the noise rejection achieved with various configurations. For better resolution and increased noise rejection, select a longer integration time.

Digits		NPLCs	Integration Time		NMR
Digits		NPLCs	60 Hz (50 Hz)		NMR

41⁄2 Fast		0.02	400 ∝s	(400 ∝s)	–
41⁄2 Slow		1	16.7 ms	(20 ms)	60 dB
51⁄2	Fast	0.2	3 ms	(3 ms)	–
51⁄2	Slow	10	167 ms	(200 ms)	60 dB
61⁄2	Fast	10	167 ms	(200 ms)	60 dB
61⁄2	Slow	100	1.67 sec (2 sec)		60 dB

200

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.

Agilent Technologies 34401A Rejecting Power-Line Noise Voltages, Digits NPLCs Integration Time

Models: 34401A