Agilent Technologies 3458A User Manual

108 Chapter 4 Making Measurements
The following program transfers readings directly to the controller at the
fastest possible rate. This program configures the multimeter to take readings
at its maximum rate of >100k readings per second. Readings are output using
the SINT format. If the bus/controller cannot transfer readings at >200k bytes
per second, the reading rate will be slower.This is because, in the
high-speed mode, the multimeter waits until each reading is removed from
its output buffer before placing the next reading in the output buffer. In the
following program, the SYN trigger arm event is used to trigger the readings
(TRIG SYN could also be used). The SYN event is very important for
high-speed operation since it ensures the controller will be ready to accept
the first reading output by the multimeter. The TRANSFER statement (line
120) satisfies the SYN event and is the fastest way to transfer readings across
the GPIB, especially when used with the direct memory access (DMA) GPIB
interface.
10 OPTION BASE 1 !COMPUTER ARRAY NUMBERING STARTS AT 1
20 INTEGER Num_readings !DECLARE VARIABLE
30 INTEGER Int_rdgs(l:30000) BUFFER !CREATE INTEGER ARRAY FOR BUFFER
40 REAL Rdgs(l:30000) !CREATE REAL ARRAY
50 Num_readings=30000 !NUMBER OF READINGS = 30000
60 ASSIGN @Dvm TO 722 !ASSIGN MULTIMETER ADDRESS
70 ASSIGN Int_rdgs TO BUFFER Int_rdgs(*) !ASSIGN BUFFER I/O PATH NAME
80 OUTPUT @Dvm; "PRESET FAST" !TARM SYN,TRIG AUTO, DCV 10V
90 OUTPUT @Dvm;"APER 1.4E-6" !1.4µs INTEGRATION TIME
100 OUTPUT @Dvm; "OFORMAT SINT" !SINT OUTPUT FORMAT
110 OUTPUT @Dvm; "NRDGS"; Num_readings !30000 READINGS/TRIGGER, AUTO
115 !SAMPLE EVENT (DEFAULT VALUE)
120 TRANSFER @Dvm TO @Int rdgs;WAIT !SYN EVENT, TRANSFER READINGS INTO
121 !INTEGER ARRAY; SINCE THE COMPUTER'S INTEGER FORMAT IS THE SAME AS
125 !SINT,NO DATA CONVERSION IS NECESSARY HERE (INTEGER ARRAY REQUIRED)
130 OUTPUT @Dvm; "ISCALE?" !QUERY SCALE FACTOR FOR SINT FORMAT
140 ENTER @Dvm;S !ENTER SCALE FACTOR
150 FOR I=1 TO Num_readings
160 Rdgs(I)=Int_rdgs(I) !CONVERT EACH INTEGER READING TO REAL
165!FORMAT (NECESSARY TO PREVENT POSSIBLE INTEGER OVERFLOW ON NEXT LINE)
170 R=ABS(Rdgs(I)) !USE ABSOLUTE VALUE TO CHECK FOR OVLD
180 IF R>=32767 THEN PRINT "OVLD" !IF OVLD, PRINT OVERLOAD MESSAGE
190 Rdgs(I)=Rdgs(I)*S !MULTIPLY READING TIMES SCALE FACTOR
200 Rdgs(I)=OROUND(Rdgs(I),4) !ROUND TO 4 DIGITS
210 NEXT I
220 END
High-Speed Transfer
from Memory
Configuring the reading memory format (MFORMAT command) to match
the output format (OFORMAT command) helps to ensure command) to
match the fastest transfer of readings from reading memory to the controller.
This is because no conversion is necessary when the readings are recalled
from memory. For high-speed, low resolution readings (3.5 or 4.5 digits)
made on a fixed range, use the SINT format. (Because the SINT format uses
only 2 bytes per reading, multiple readings can be stored in memory and
transferred across the bus faster using the SINT output format than any other
format.) For the fastest transfer of high resolution readings (5.5 digits or
greater) made on a fixed range, use the DINT format. Whenever autorange
is enabled and transfer speed is critical, use the SREAL format (for readings
of 6.5 digits or less) or the DREAL format (for readings of 7.5 or 8.5 digits).
Disabling the display and any math operations will also ensure the fastest
transfer from reading memory to the controller.

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