Fluke 8840A User Manual

Remote Programming
INPUT SYNTAX
In some instances, a terminator is automatically transrnit-
ted at the end of the controller's output string. For exam-
ple, in Fluke BASIC, the PRINT statement always finishes
with a CR
LF pair. If a controller does not have this
feature, the programmer must transmit a terminator explic-
itly.
The 8840A accepts alphabetic characters in either upper or
lower case. Spaces, commas, and control codes are ignored
and are not placed in the input buffer. If the 8840A
receives
a group of terminators (such as CR LF or CR LF
EOI), only a single terminator is loaded into the input
buffer. Numeric values used in
PUT commands may be in
NRl, NR2, or NR3 format
as described in the IEEE-488
Codes and Formats Recommended Practice. (These corres-
pond to the signed integer, real number, and real-number-
with-exponent formats described under the
N command.)
For reference, 'Figure
3-8 shows how the 8840A interprets
messages.
Illegal commands
(e-g., F9) generate
an enor message, but
are otherwise ignored, and do not affect the instrument's
configuration.
Example Explanation
4,* Fg"
This would load the output buffer
with an error message and select F1
(established by the
* command).
3-39. Syntax Rules
Four syntax rules should be followed when constructing
input command strings. They are:
RULE 1: Read output data only once.
To prevent old (previously read) data from being read
a second time by mistake, the output buffer is always
cleared after it has been read. If the output buffer is
read twice without
an intervening output command,
the 8840A will not respond to the second attempt to
read the output buffer. (However, if the
8840A is in
TO, no intervening command is necessary.)
RULE 2: Use no more than one output command per
input command string.
Because the 8840A has only one output buffer, it
writes new data over old. If
an input command string
contains more than one output command, only the
data from the last command
can be read.
Example
"F1
T3 ? F2 ?"
"F2 R3 SO"
Explanation
Improper construction. The second
trigger writes over the first. To
obtain two readings, send two
complete command strings (sepa-
rated by terminators).
Correct construction. The string
contains only one output com-
mand.
Correct construction. It is permissi-
ble for
a string not to contain an
output command.
RULE 3: Read the output data generated by one input
command string before sending the next input com-
mand string.
Output data remains available in the output buffer
until it is read, or until the next input command string
is received.
As soon as the controller finishes reading
the output buffer, or as soon as the
8840A receives a
new input terminator, the Data Available bit in the
serial poll register is set
false. When
this bit is false,
data
can no longer be read from the output buffer.
Therefore,
an output string which is available must be
read by the controller before, rather than after, the
next input command string is sent.
Rule
3 is most evident in the external trigger mode,
and is best demonstrated by a programming example.
The following program is written first incorrectly, and
then correctly, in Fluke BASIC using the 1722A
Instrument Controller.
Incorrect example:
100 PRINT
@3, "TI ?*
200 PRINT
@3, "F4"
300
INPUT @3, A
In this inconect example, the INPUT statement is
located incorrectly for reading the measurement
data
from line 100. The new input command string "F4"
disallows the reading of data from the output buffer.
Correct example:
100 PRINT
83, "T1 7"
200
INPUT @3, A
300 PRINT
@3, "F4"
In this example, the reading taken at line 100 is read
at line 200. Then the F4 command is sent. Note that in
the external trigger mode, the reading from line
100
flashes on the 8840A display too briefly to see. This is
because the function change at line
300 blanks the
display until the next trigger.
The previous example could also
be correctly pro-
grammed as follows:
100 PRINT @3, "TI ? F4"
200 INPUT @3, A
Rule 4: If an input command string contains a trigger,
enter the commands in the following order:
a Commands to configure the instrument (if any).
b. The trigger command
c.
Commands to re-configure the instrument (if
any).
The principle behind this rule is that the 8840A executes
all commands in the exact order they are received, from
left to right as written.
Example Explanation
"F3 F4
?"
Improper construction. F3 is effectively
discarded.
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Fluke 8840A Specifications

General

Frequency Range	20 Hz to 100 kHz
Operating Temperature	0°C to 50°C
Display	Vacuum Fluorescent
DC Current Range	0 to 2 A
AC Current Range	0 to 2 A

Summary

Introduction and Specifications

Technical Specifications Overview

Presents the detailed technical specifications for the 8840A multimeter.

Operating Instructions

Installation Procedures

Connecting to Line Power

Instructions on how to properly connect the 8840A to a power source, including voltage selection.

Operating Features Overview

Display Features and Error Messages

Explains the display, error messages, and overrange indication.

Diagnostic Self-Tests and Ranging

Covers running self-tests, selecting measurement ranges, and trigger modes.

Making Measurements

Provides procedures for performing various measurements and understanding input protection.

Remote Programming

IEEE-488 Interface Capabilities

Bus Set-up Procedure

Steps for connecting and configuring the 8840A for IEEE-488 bus operation.

Device-Dependent Command Set

Lists commands that control specific instrument functions like measurements and requests.

Cn Calibration Commands

G2 Get Calibration Prompt

G4 Get Calibration Status

G7 Get Error Status

Retrieves the instrument's error status register, indicating any errors encountered.

P0 Put Instrument Configuration

Command to load function, range, reading rate, and trigger mode settings.

P1 Put SRQ Mask

P2 Put Calibration Value

Command to enter variable input calibration values.

Rn Range Commands

X0 Clear Error Register Command

Clears the instrument's error status register without affecting other settings.

Z0 Self-Test Command

Initiates the instrument's diagnostic self-tests.

* Device-Clear Command

Resets the instrument to power-up default settings and clears buffers.

Numeric Data and Error Messages

Details the format for numeric data, overrange indications, and error messages.

Error Message Format

Describes the format for error messages, including error codes and suppression of suffix.

Understanding Service Requests

The Serial Poll Register

Describes the serial poll register and how it indicates status and SRQ events.

Remote Calibration Procedure

Instructions for calibrating the instrument remotely using the IEEE-488 interface.

Example Programs for Remote Control

Measurement Tutorial

DC Voltage Measurement Basics

Explains how to measure DC voltages, covering circuit loading and input bias current errors.

Understanding Circuit Loading Error

Correcting for Input Bias Current Error

Provides a procedure to correct for input bias current errors using the OFFSET function.

Resistance Measurement Techniques

Explains how to measure resistance using 2-wire and 4-wire configurations.

Correcting 2-Wire Ohms Test Lead Resistance

4-Wire Ohms Measurement

Explains the 4-wire ohms measurement for high accuracy, correcting for lead and contact resistance.

DC Current Measurement and Burden Voltage

Explains DC current measurement, focusing on burden voltage error and its calculation.

AC Voltage and Current Measurement Considerations

True RMS Measurement Explained

Explains the True RMS AC Option for measuring AC voltages and currents accurately.

Theory of Operation

Overall Functional Description

Detailed Circuit Description

Provides detailed explanations of each functional block, including component references.

DC Scaling Circuit Overview

VDC Input Protection

Details the protection circuitry for DC voltage inputs, including MOVs and fusible resistors.

Track/Hold (T/H) Circuit Overview

Precision Voltage Reference

Ohms Current Source Operation

Explains the precise current source used in ohms functions and its troubleshooting uses.

Ohms Protection Circuitry

2-Wire Ohms Measurement Details

4-Wire Ohms Measurement Details

Explains the 4-wire ohms measurement for high accuracy, including lead resistance correction.

Analog-to-Digital (A/D) Converter

Explains the A/D converter, its components, and the recirculating remainder technique.

Precision Digital-to-Analog Converter (DAC)

A/D Amplifier Circuit

Digital Controller Overview

Explains the function of the Digital Controller and its components like the In-Guard Microcomputer.

In-Guard Microcomputer (µC) Details

Function and Range Control

A/D Control and Computation

Details how the µC controls A/D sampling, rates, and calibration.

Calibration Correction Memory

Troubleshooting Modes of Operation

Explains the troubleshooting mode for diagnosing digital hardware issues.

Guard Crossing Communication

Describes the circuit enabling communication between the Digital Controller and IEEE-488 interface.

Bus Interface Circuitry

In-Guard Microcomputer System Checks

Checks for the In-Guard µC and its associated signals in troubleshooting mode.

Maintenance Troubleshooting

Troubleshooting In-Guard Microcomputer

Details waveforms for troubleshooting the In-Guard Microcomputer system.

Maintenance

Performance Testing Procedures

Details tests to verify instrument performance against specifications.

Diagnostic Self-Tests

Instructions on running built-in tests to diagnose instrument hardware issues.

DC Voltage Test Procedure

Procedure to verify the accuracy of the DC voltage measurement function.

AC Voltage Test (Option -09 Only)

Procedure to verify the accuracy of the AC voltage measurement function.

Resistance Measurement Test

Procedure to verify the accuracy of the 2-wire and 4-wire ohms functions.

DC Current Measurement Test

Procedure to test the accuracy of the mA DC current measurement function.

AC Current Test (Option -09 Only)

Calibration Procedures Overview

Introduces the calibration process, including basic and advanced procedures.

Basic Calibration Procedure Steps

Outlines the four main parts of the basic calibration process.

Initial Calibration Procedure Steps

A/D Converter Calibration

Calibrates the analog-to-digital converter for offset, gain, and linearity.

Offset and Gain Calibration

Calibrates the instrument's offsets and gains for each function and range.

High-Frequency AC Calibration

Erasing Calibration Memory

Remote Calibration Process

Disassembly Procedure Overview

Front Panel Disassembly Steps

Reassembly Procedure Guidelines

Internal Fuse Replacement

Troubleshooting General Problems

Guidance on approaching troubleshooting, starting with power supplies and self-tests.

Diagnostic Self-Tests Details

Provides detailed descriptions of each self-test and how to interpret results.

DC Scaling Troubleshooting Guide

Troubleshooting steps for the DC Scaling circuit, including power supply and signal checks.

Track/Hold Circuit Troubleshooting

A/D Converter Troubleshooting

Steps for diagnosing A/D converter failures, including checking supplies and waveforms.

Power Supply Troubleshooting

Procedure for diagnosing power supply issues, checking voltages, ripple, and load regulation.

IEEE-488 Interface Troubleshooting

True RMS AC Troubleshooting (Option -09)

Troubleshooting steps for the True RMS AC option, including signal flow and PCA checks.

Major Problems Identification