Agilent Technologies 3458A User Manual

Chapter 6 Command Reference 199
MFORMAT
The format parameter choices are:
* The ASCII format is actually 15 bytes for the reading plus 1 byte for a null character
which is used to separate stored ASCII readings only.
Power-on format = SREAL.
Default format = SREAL.
Remarks • The multimeter indicates an overload by storing the value ± 1E+38 in memory
instead of the reading. When overload values are recalled to the display, the
value
± 1E+38 is displayed. When overload values are transferred from reading
memory to the GPIB output buffer, they are converted to the overload number
for the specified output format. (See the OFORMAT command for details.)
• When using the SINT or DINT memory format, the multimeter stores each
reading assuming a certain scale factor. This scale factor is based on the present
measurement function, range, A/D setting, and enabled math operations. When
you recall a reading, the multimeter calculates the scale factor based on the
present measurement function, range, A/D setting, and enabled math operations.
It then multiplies the scale factor by the stored reading and sends the result
(recalled reading) to the display or the output buffer. Therefore, always ensure
that the multimeter's configuration is the same when storing and recalling data
in the SINT or DINT format.
• You should not use the SINT or DINT output or memory format for frequency
or period measurements when a real-time or post-process math function is
enabled (except STAT or PFAIL) or when autorange is enabled.
• The memory format does not affect the output format specified by the
OFORMAT command.
• You enable reading memory using the MEM command. You access stored
readings using the RMEM command or by using the "implied read." The
"implied read" is discussed under "Using Reading Memory" in Chapter 4.
• When using reading memory for sub-sampled measurements (SSAC or SSDC
command), the memory format must be set to SINT, the memory mode must be
format
Parameter
Numeric
Query
Equiv. Description
ASCII 1 ASCII-16 bytes per reading*
SINT 2 Single Integer-16 bits 2's complement (2 bytes per
reading)
DINT 3 Double Integer-32 bits 2's complement (4 bytes per
reading)
SREAL 4 Single Real-(IEEE-754) 32 bits (4 bytes per
reading)
DREAL 5 Double Real-(IEEE-754) 64 bits (8 bytes per
reading)

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