Agilent Technologies 3458A User Manual

Chapter 5 Digitizing 135
The PRESET DIG command configures the multimeter for DC voltage
measurements with a sampling rate of 50,000 samples per second. PRESET
DIG selects a 3µs integration time and level triggering when the input signal
crosses zero volts on its positive slope. The primary commands executed by
PRESET DIG are:
TARM HOLD -- Suspends triggering
TRIG LEVEL -- LEVEL trigger event
LEVEL 0,AC -- Level trigger at 0% of range (0V), AC-coupled
TIMER 20E-6 -- 20µs interval between samples
NRDGS 256,TIMER -- 256 samples per trigger, TIMER sample event
DCV 10 -- DC voltage measurements, 10V range
DELAY 0 -- No delay
APER 3E-6 -- 3µs integration time
MFORMAT SINT -- Single integer memory format
OFORMAT SINT -- Single integer output format
AZERO OFF -- Disables the autozero function
DISP OFF -- Disables the display
After executing PRESET DIG, you can increase the sampling rate by
decreasing the TIMER interval and by reducing the integration time using
the APER command. The minimum integration time for DCV is 500
nanoseconds.
DCV Remarks • For DCV digitizing, you should use the SINT memory/output format when
the integration time is £ 1.4µs. Use the DINT memory/output format when
the integration time is >1.4µs. (These formats are discussed in detail in
Chapter 4.)
Note To achieve the fastest possible transfer of samples to reading memory and/or the
controller, you can use the SINT output/memory format for integration times up to
10.8ms. However when the integration time is >1.4ms, the A/D converter is
producing more bits of resolution than can be accommodated by the SINT format
(the least significant bit(s) are discarded). Whenever using the SINT
output/memory format with integration times >10.8ms, the multimeter must
convert the data coming from the A/D converter and cannot maintain the
high-speed mode. You should use the DINT memory/output format (which is
compatible with the high-speed mode) when the integration time is >10.8ms.
• Whenever making measurements using the TIMER sample event or the
SWEEP command, autorange is disabled. You can use the range selected
by PRESET DIG (10V range) or specify the range as the first parameter
of the DCV or RANGE command (max_input parameter). The max_input
parameters and the ranges they select are:

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