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Keithley 6514 User Manual

Keithley 6514
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Amps Measurements 4-9
NOTES The format that the reading string is returned in is set by commands in the FORMat
Subsystem (see Section 16).
If there is no reading available when :DATA? is sent, an error (-230) will occur.
The READ? command can be used to return “fresh” readings. This command triggers
and returns the readings. See Section 15 for details.
Programming example
The following command sequence will perform one zero corrected amps measurement:
*RST ‘ Return 6514 to RST defaults.
SYST:ZCH ON ‘ Enable zero check.
FUNC ‘CURR’ ‘ Select the Amps function.
CURR:RANG 20e-12 ‘ Select the 20pA range.
SYST:ZCOR ON ‘ Perform zero correction.
CURR:RANG:AUTO ON ‘ Enable auto range.
SYST:ZCH OFF ‘ Disable zero check.
READ? ‘ Trigger and return one reading.
Amps measurement considerations
Some considerations for making accurate amps measurements are summarized as follows.
Additional measurement considerations are covered in Appendix C. For comprehensive infor-
mation on precision measurements, refer to the Low Level Measurements handbook, which is
available from Keithley Instruments.
Input bias current
An ideal ammeter would read 0A with an open input. In practice, however, ammeters do have
some current that flows when the input is open. This current is known as the input bias (offset)
current and may be large enough to corrupt low current measurements.
The input bias current for Model 6514 is listed in the specifications. Input bias current may
be reduced by performing the current offset correction procedure explained in Section 19.
Voltage burden
The input resistance of the ammeter causes a small voltage drop across the input terminals.
This voltage is known as the voltage burden. If the voltage burden is large in relation to the volt-
age of the measured circuit, then significant measurement errors will occur.
Refer to Figure 4-4 to see how voltage burden affects current measurements. Assume V
S
is
5mV and R
S
is 5k to configure a 1uA current source (5mV/5k = 1µA). An ideal ammeter
with zero voltage burden would measure the current source as follows:
I
M
E
S
R
S
------
5mV
5k
------------ 1µA== =

Table of Contents

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Keithley 6514 Specifications

General IconGeneral
BrandKeithley
Model6514
CategoryMeasuring Instruments
LanguageEnglish

Summary

Getting Started

System Electrometer Features

Overview of the Model 6514's measurement capabilities and features.

Front and Rear Panel Familiarization

Identification and function of front and rear panel controls and connectors.

Power-up

Procedures for connecting line power and turning the instrument on.

Measurement Concepts

Performance Considerations

Factors affecting overall instrument performance, including warm-up and autozero.

Connection Fundamentals

Basic information on connecting test circuits to the electrometer.

Zero Check and Zero Correct

Operation details for zero check and zero correct functions for accurate measurements.

Volts and Ohms Measurements

Guarding

Explanation of guarding techniques to eliminate leakage and improve accuracy in high-impedance measurements.

Volts and Ohms Measurement Procedure

Step-by-step guide for performing voltage and resistance measurements.

Amps Measurements

High-Impedance Measurement Techniques

Techniques to eliminate leakage currents in high-impedance test circuits for accurate current measurements.

Amps Measurement Considerations

Factors affecting current measurements, including bias current and voltage burden.

Coulombs Measurements

Auto Discharge

How to use the auto discharge feature for coulombs measurements, resetting charge readings.

Coulombs Measurement Procedure

Step-by-step guide for measuring charge using the instrument.

Range, Units, Digits, Rate, and Filters

Range, Units, and Digits

Details on selecting measurement range, display units, and resolution.

Filters

Configuration and control of digital and median filters to stabilize noisy measurements.

Relative, mX+b and Percent (%)

Relative

Explanation of nulling offsets or establishing baseline values for measurements.

mX+b and Percent (%)

Covers mathematical operations for scaling and percent deviation calculations.

Buffer

Buffer Operations

Procedures for storing and recalling readings, including buffer statistics.

Triggering

Trigger Models

Components and configuration of trigger models controlling instrument operations.

External Triggering

Using external signals to trigger or be triggered by other instruments.

Limit Tests

Limit Testing

Performing wide and narrow pass band tests to evaluate device tolerance.

Binning

Using digital outputs with component handlers for sorting devices based on test results.

Digital I/O, Analog Outputs, and External Feedback

Digital I/O Port

Using the digital I/O port for controlling external circuitry and component handlers.

External Feedback

Extending measurement capabilities using external feedback networks for specialized applications.

Remote Operation

Selecting and Configuring an Interface

How to select and configure GPIB or RS-232 interfaces for remote control.

GPIB Operation and Reference

Details on GPIB bus standards, connections, and operation.

RS-232 Interface Reference

Information on RS-232 settings, connections, and communication protocols.

Status Structure

Status Byte and Service Request (SRQ)

Programming the status byte to generate and detect service requests.

Status Register Sets

Bit identification and commands for standard, operation, measurement, and questionable event registers.

Common Commands

Common Commands

IEEE-488.2 standard device commands common across instruments.

SCPI Signal Oriented Measurement Commands

Signal Oriented Measurement Commands

High-level SCPI commands for controlling measurement acquisition.

DISPlay, FORMat, and SYSTem

DISPlay Subsystem

SCPI commands to control the instrument's display and user messages.

FORMat Subsystem

SCPI commands to configure data transfer formats over the bus.

SYSTem Subsystem

Miscellaneous SCPI commands for instrument configuration and control.

SCPI Reference Tables

General Notes

Explains SCPI command syntax, parameter types, and conventions used in reference tables.

Performance Verification

Verification Test Requirements

Conditions and prerequisites for performing instrument verification tests accurately.

Recommended Test Equipment

List of recommended equipment and their specifications for performance verification.

Performing the Verification Test Procedures

Step-by-step procedures to verify measurement accuracy for each function.

Calibration

Calibration Cycle

Recommended frequency for performing calibration to ensure optimal performance.

Recommended Calibration Equipment

List of recommended equipment for calibration procedures.

Calibration Procedure

Step-by-step guide for performing instrument calibration.

Routine Maintenance

Setting Line Voltage and Replacing Line Fuse

Procedures for setting line voltage and replacing the instrument's fuse.

Front Panel Tests

Running self-tests for the display and front panel keys to verify functionality.

Specifications

VOLTS

Detailed specifications for voltage measurements, including accuracy and coefficients.

AMPS

Detailed specifications for current measurements, including accuracy and bias.

OHMS

Detailed specifications for resistance measurements, including accuracy and test current.

COULOMBS

Detailed specifications for charge measurements, including accuracy and bias current.

IEEE-488 BUS IMPLEMENTATION

Requirements and details for IEEE-488 bus interface implementation.

RS-232 IMPLEMENTATION

Requirements and details for RS-232 serial interface implementation.

GENERAL

General specifications covering display, ranging, conversion time, and physical dimensions.

Status and Error Messages

Error Messages

List of status and error codes with descriptions and event types.

General Measurement Considerations

Ground Loops

How ground loops in multi-instrument setups cause measurement errors and how to prevent them.

Electrostatic Interference

Sources and effects of electrostatic interference on measurements and methods for minimization.

Electromagnetic Interference (EMI)

Sources of EMI and precautions for sensitive measurements.

DDC Emulation Commands

DDC Language

Information on using device-dependent commands (DDCs) for controlling the instrument.

Example Programs

Programming Examples

Examples demonstrating various programming tasks and instrument control.

One-Shot Triggering

Setting up the instrument for one-shot triggering to acquire single readings.

Storing Readings in Buffer

Demonstrates setting up the buffer and reading data after it has filled.

IEEE-488 Bus Overview

Bus Description

Overview of the IEEE-488 bus, its architecture, and device operators.

Bus Commands

Description of uniline, multiline, common, and SCPI bus commands.

Interface Function Codes

Defines instrument capabilities related to IEEE-488 interface functions.

IEEE-488 and SCPI Conformance Information

Introduction

Overview of IEEE-488.2 and SCPI standard requirements and Model 6514 compliance.

Calibration Options

Remote Calibration

Procedures for performing instrument calibration using remote commands.

Calibration Commands

Summary of SCPI commands used for instrument calibration.

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