Agilent Technologies 3458A User Manual

94 Chapter 4 Making Measurements
The SREAL number is then calculated by:
-1
´ 2
-8
´ 1.56471443177 = -6.1121657491E-3
Double Real The double real (DREAL) format conforms to IEEE-754 specifiations and
contains 64 bits (8 bytes) per reading as follows:
byte 0 byte 1 byte 2 byte 3
S EEE EEEE EEEE MMMM MMMM MMMM MMMM MMMM
byte 4 byte 5 byte 6 byte 7
MMMM MMMM MMMM MMMM MMMM MMMM MMMM MMMM
Where:
S = sign bit (1 = negative 0 = positive)
E = base two exponent biased by 1023 (to decode these 11 bits, subtract 1023
from their decimal equivalent).
M = mantissa bits (those right of the radix point). There is an implied most
significant bit (MSB) to the left of the radix point. This bit is always "1".
This provides an effective precision of 53 bits with the least significant bit
(right most) weighted 2
-52
. Another way to evaluate this mantissa is to
convert these 53 bits (MSB = "1") to an integer and then multiply by 2
-52
.
The value of a number in the DREAL format is calculated by:
(-1)
S
´ (mantissa) ´ 2
(exponent)
Using Reading Memory
The multimeter stores readings in memory whenever readings are being
taken and reading memory is enabled. Reading memory has a FIFO
(first-in-first-out) mode and a LIFO (last-in-first-out) mode. In the FIFO
mode, the first reading stored is the first reading returned when you recall
readings without specifying reading numbers (implied read method which is
discussed later in this chapter). If you fill the reading memory in the FIFO
mode, all stored readings remain intact and new readings are not stored.
In the LIFO mode, the last reading stored is the first reading returned when
you recall readings without specifying reading numbers. If you fill reading
memory in the LIFO mode, the oldest readings are replaced by the newest
readings. You enable reading memory and specify the mode using the MEM
command. (Specifying a reading memory mode erases any previously stored
readings.) For example, to specify reading memory using the LIFO mode,
send:
OUTPUT 722."MEM LIFO"
The multimeter is now enabled to store readings. After storing readings, you
can disable reading memory and leave all stored readings intact by sending:
OUTPUT 722;"MEM OFF"
Later, you can resume the previous mode to store additional readings without

Agilent Technologies 3458A Specifications

General

Model	3458A
Manufacturer	Agilent Technologies
Category	Multimeter
Digits	8.5
Sampling Rate	100, 000 readings/second
Interface	GPIB

Summary

Safety Symbols and Warnings

General Safety Precautions (WARNINGS)

Outlines essential safety precautions for operating, servicing, and repairing the product to prevent injury or damage.

Chapter 2 Getting Started

Operating from the Front Panel

Covers using front panel keys, making measurements, changing functions, and controlling display settings.

Operating from Remote

Explains how to control the multimeter remotely via GPIB, including address management and command sending.

Chapter 3 Configuring for Measurements

General Configuration

Configuring for DC or Resistance Measurements

Details how to configure the multimeter for DC voltage, DC current, and 2-wire or 4-wire resistance measurements.

Configuring for AC Measurements

Explains how to configure the multimeter for AC voltage, AC current, frequency, or period measurements.

Chapter 4 Making Measurements

Triggering Measurements

Explains the three-event triggering hierarchy (arm, trigger, sample) and various event choices.

Using Reading Memory

Sending Readings Across the Bus

Increasing the Reading Rate

Discusses the multimeter's high-speed mode and factors affecting reading rate and transfer speed.

Math Operations

Explains real-time and post-process math operations, enabling/disabling them, and math registers.

Chapter 5 Digitizing

Digitizing Methods

Details DCV, Direct-Sampling, and Sub-sampling methods, summarizing their characteristics and signal paths.

The Sampling Rate

Level Triggering

Describes how to specify voltage and slope for sampling initiation, with examples for DCV and direct-sampling.

DCV Digitizing

Direct-Sampling

Explains direct-sampling using track-and-hold, its bandwidth, and specifying ranges via max._input parameter.

Sub-Sampling

Covers sub-sampling fundamentals, advantages, and how to specify effective interval and number of samples.

Chapter 6 Command Reference

ACAL

Instructs the multimeter to perform self-calibrations (ALL, DCV, AC, OHMS) and discusses autocalibration security.

NRDGS

OFORMAT

PRESET

Configures the multimeter to one of three predefined states: NORM, FAST, or DIG for different operation modes.

SUB

Stores a series of commands as a subprogram, assigning a name for later execution.

TARM

Defines the trigger arm event to enable the trigger event and can be used for multiple measurement cycles.

TEST

Causes the multimeter to perform a series of internal self-tests to check hardware and software integrity.

TRIG

Specifies the trigger event that initiates a measurement, working with TARM and NRDGS.

Chapter 7 BASIC Language for the 3458A

BASIC Language Commands

Subprograms

Explains how to store, execute, and manage BASIC language subprograms for system control and automation.

Appendix B GPIB Commands

TRIGGER (GET)

Appendix C Procedure to Lock Out Front/Rear Terminals and Guard Terminal Switches

Procedure

Outlines the steps for installing the switch lockout kit, including covers and pushrod removal.

Appendix D Optimizing Throughout and Reading Rate

Maximizing the Testing Speed

Covers strategies like tailoring communication paths, program memory, and state storage for optimal testing speed.

DC Volts, DC Current and Resistance

Explains the measurement paths (DCV, track-and-hold) and trade-offs for DC measurements.

AC Volts and AC Current

Details the three ACV measurement techniques (Analog, Synchronous, Random) and their trade-offs.

Frequency and Period

Optimizing the Testing Process Through Task Allocation

Discusses allocating tasks between the DMM and computer using math functions, memory, and program structure.

Math Operations

State Storage and Program Memory

A Benchmark

Appendix E High Resolution Digitizing With the 3458A

Speed with Resolution

Details the multimeter's flexibility in speed and resolution for audio frequency bandwidth.

Digitizing Analog Signals

Avoiding Aliasing

Provides methods to avoid signal distortion caused by aliasing, ensuring accurate waveform representation.

Choice of Two Measurement Paths

Describes the standard DCV path and the track-and-hold path for digitizing and sampling.

Capturing the Data

High Speed Data Transfers

Errors in Measurements