Measurement Computing USB-1408FS User Manual

USB-1408FS

USB-based

Analog and Digital I/O Module

User's Guide

Document Revision 5, March, 2008

© Copyright 2008, Measurement Computing Corporation

HM USB-1408FS.doc

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3

Trademark and Copyright Information

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Notice

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4

Table of Contents

Preface

About this User's Guide ....................................................................................................................... 7

What you will learn from this user's guide ......................................................................................................... 7

Conventions in this user's guide ......................................................................................................................... 7

Where to find more information ......................................................................................................................... 7

Chapter 1

Introducing the USB-1408FS................................................................................................................ 8

USB-1408FS block diagram ............................................................................................................................... 9

Software features ................................................................................................................................................ 9

Connecting a USB-1408FS to your computer is easy....................................................................................... 10

Chapter 2

Installing the USB-1408FS .................................................................................................................. 11

What comes with your USB-1408FS shipment? .............................................................................................. 11

Hardware .........................................................................................................................................................................11

Additional documentation ................................................................................................................................................11

Unpacking the USB-1408FS ............................................................................................................................ 12

Installing the software ...................................................................................................................................... 12

Installing the hardware ..................................................................................................................................... 12

Calibrating the USB-1408FS ............................................................................................................................ 13

Chapter 3

Functional Details ............................................................................................................................... 14

Theory of operation - analog input acquisition modes ..................................................................................... 14

Software paced mode .......................................................................................................................................................14

Continuous scan mode .....................................................................................................................................................14

External components ........................................................................................................................................ 14

USB connector .................................................................................................................................................................15

LED .................................................................................................................................................................................15

Screw terminal wiring ......................................................................................................................................................15

Main connector and pin out .............................................................................................................................................16

Analog input terminals (CH0 IN - CH7 IN).....................................................................................................................16

Analog output terminals (D/A OUT 0 and D/A OUT 1) ................................................................ ..................................19

Digital I/O terminals (Port A0 to A7, and Port B0 to B7) ................................................................................................19

Power terminals ...............................................................................................................................................................20

External trigger terminal ..................................................................................................................................................20

Counter terminal ..............................................................................................................................................................20

+2.5VREF terminal ..........................................................................................................................................................21

SYNC terminal ................................................................................................................................................................21

Ground terminals .............................................................................................................................................................21

Accuracy ........................................................................................................................................................... 21

USB-1408FS channel gain queue feature ......................................................................................................... 24

Synchronizing multiple units ............................................................................................................................ 24

Chapter 4

Specifications ...................................................................................................................................... 26

Analog input ..................................................................................................................................................... 26

Analog output ................................................................................................................................................... 28

Digital input/output........................................................................................................................................... 28

External trigger ................................................................................................................................................. 29

External clock input/output............................................................................................................................... 29

Counter section ................................................................................................................................................. 29

5

USB-1408FS User's Guide

Non-volatile memory ........................................................................................................................................ 30

Microcontroller ................................................................................................................................................. 30

Power ................................................................................................................................................................ 30

General ............................................................................................................................................................. 30

Environmental .................................................................................................................................................. 31

Mechanical ....................................................................................................................................................... 31

Main connector and pin out .............................................................................................................................. 31

4-channel differential mode .............................................................................................................................................31

8-channel single-ended mode ...........................................................................................................................................32

Declaration of Conformity .................................................................................................................. 33

6

Preface

About this User's Guide

What you will learn from this user's guide

This user's guide explains how to install, configure, and use the USB-1408FS, and refers you to related
documents available on our web site, and to technical support resources.

Conventions in this user's guide

For more information on …

Text presented in a box signifies additional information and helpful hints related to the subject matter you are
reading.

Caution! Shaded caution statements present information to help you avoid injuring yourself and others,

damaging your hardware, or losing your data.

< : > Angle brackets that enclose numbers separated by a colon signify a range of numbers, such as those assigned

to registers, bit settings, etc.

bold text Bold text is used for the names of objects on the screen, such as buttons, text boxes, and check boxes. For

example:

1. Insert the disk or CD and click the OK button.

italic text Italic text is used for the names of manuals and help topic titles, and to emphasize a word or phrase. For

example:
The InstaCal installation procedure is explained in the Quick Start Guide.
Never touch the exposed pins or circuit connections on the board.

Where to find more information

 MCC's Specifications: USB-1408FS (the PDF version of the Specifications chapter in this guide) is

available on our web site at www.mccdaq.com/pdfs/USB-1408FS.pdf.

 MCC's Quick Start Guide is available on our web site at

 MCC's Guide to Signal Connections is available on our web site at

www.mccdaq.com/signals/signals.pdf.

 MCC's Universal Library User's Guide is available on our web site at

 MCC's Universal Library Function Reference is available on our web site at

 MCC's Universal Library for LabVIEW™ User’s Guide is available on our web site at

USB-1408FS User's Guide (this document) is also available on our web site at

7

Chapter 1

Introducing the USB-1408FS

This user's guide contains all of the information you need to connect the USB-1408FS to your computer and to
the signals you want to measure.

The USB-1408FS is a USB 2.0 full-speed, device that is supported under popular Microsoft® Windows®
operating systems. The USB-1408FS is fully compatible with both USB 1.1 and USB 2.0 ports.

The USB-1408FS features eight analog inputs, two 12-bit analog outputs, 16 digital I/O connections, and one
32-bit external event counter.

The analog inputs are software configurable for either eight 13-bit single-ended inputs or four 14-bit differential
inputs. The 16 digital I/O lines are independently selectable as input or output in two 8-bit ports. The 32-bit
counter can count TTL pulses. A SYNC (synchronization) input/output line allows you to pace the analog input
acquisition of one USB module from the clock output of another.

The USB-1408FS is powered by the +5 volt USB supply from your computer. No external power is required.

The USB-1408FS is shown in Figure 1. I/O connections are made to the screw terminals located along each side
of the USB-1408FS.

Figure 1. USB-1408FS

8

USB-1408FS User's Guide Introducing the USB-1408FS

Screw terminal I/O connector

SPI

8

DIO

Event Counter

1 channel

(32-bit)

USB

Microcontroller

SYNC

16

USB

Full-speed

USB 2.0

Compliant

Interface

Screw terminal I/O connector

TRIG_IN

Port A

Port B

1

Analog Input

8 single-ended

(13-bit) channels

or

4 differential

(14-bit) channels

8

Analog Output

2

(12-bit)

channels

2

USB-1408FS block diagram

USB-1408FS functions are illustrated in the block diagram shown here.

Software features

For information on the features of InstaCal and the other software included with your USB-1408FS, refer to the
Quick Start Guide that shipped with your device. The Quick Start Guide is also available in PDF at

Check www.mccdaq.com/download.htm for the latest software version.

Figure 2. USB-1408FS functional block diagram

9

USB-1408FS User's Guide Introducing the USB-1408FS

Connecting a USB-1408FS to your computer is easy

Installing a data acquisition device has never been easier.
 The USB-1408FS relies upon the Microsoft Human Interface Device (HID) class drivers. The HID class

drivers ship with every copy of Windows that is designed to work with USB ports. We use the Microsoft
HID because it is a standard, and its performance delivers full control and maximizes data transfer rates for
your USB-1408FS. No third-party device driver is required.

 The USB-1408FS is plug-and-play. There are no jumpers to position, DIP switches to set, or interrupts to

configure.

 You can connect the USB-1408FS before or after you install the software, and without powering down

your computer first. When you connect an HID to your system, your computer automatically detects it and
configures the necessary software. You can connect and power multiple HID peripherals to your system
using a USB hub.

 You can connect your system to various devices using a standard four-wire cable. The USB connector

replaces the serial and parallel port connectors with one standardized plug and port combination.

 You do not need a separate power supply module. The USB automatically delivers the electrical power

required by each peripheral connected to your system.

 Data can flow two ways between a computer and peripheral over USB connections.

10

Installing the USB-1408FS

What comes with your USB-1408FS shipment?

As you unpack your USB-1408FS, verify that the following components are included.

Hardware

 USB-1408FS (shown with cable)

Chapter 2

 USB cable (2 meter length)

Additional documentation

In addition to this hardware user's guide, you should also receive the Quick Start Guide (available in PDF at

the software you received with your USB-1408FS and information regarding installation of that software.
Please read this booklet completely before installing any software or hardware.

11

USB-1408FS User's Guide Installing the USB-1408FS

Unpacking the USB-1408FS

As with any electronic device, you should take care while handling to avoid damage from static
electricity. Before removing the USB-1408FS from its packaging, ground yourself using a wrist strap or by
simply touching the computer chassis or other grounded object to eliminate any stored static charge.

If your USB-1408FS is damaged, notify Measurement Computing Corporation immediately by phone, fax, or e­mail. For international customers, contact your local distributor where you purchased the USB-1408FS.

 Phone: [phone] and follow the instructions for reaching Tech Support.
 Fax: [phone] to the attention of Tech Support
 Email: [e-mail]

Installing the software

Quick-Start.pdf.

Installing the hardware

Be sure you are using the latest system software

Before you install your USB-1408FS, run Windows Update to update your operating system with the latest HID
and USB drivers.

To connect the USB-1408FS to your system, turn your computer on, and connect the USB cable to a USB port
on your computer or to an external USB hub that is connected to your computer. The USB cable provides power
and communication to the USB-1408FS.

When you connect the USB-1408FS for the first time, a series of Found New Hardware popup balloons
(Windows XP) or dialogs (other Windows versions) open as the USB-1408FS is detected by your computer.

It is normal for multiple dialogs to open when you connect the USB-1408FS for the first time. For additional
information, refer to the "Notes on installing and using the USB-1408FS" that was shipped with the USB­1408FS.

The last popup balloon or dialog states "Your new hardware is installed and ready to use," and the LED on the
USB-1408FS should flash and then remain lit. This indicates that communication is established between the
USB-1408FS and your computer.

12

USB-1408FS User's Guide Installing the USB-1408FS

You can install up to two USB-1408FS units on most computers. If you need to connect more than two USB­1408FS units to your computer, contact Tech Support by phone, fax, or e-mail:

 Phone: [phone] and follow the instructions for reaching Tech Support.
 Fax: [phone] to the attention of Tech Support
 Email: [e-mail]


Caution! Do not disconnect any device from the USB bus while the computer is communicating with the

USB-1408FS, or you may lose data and/or your ability to communicate with the USB-1408FS.

If the LED turns off

If the LED is illuminated but then turns off, the computer has lost communication with the USB-1408FS. To
restore communication, disconnect the USB cable from the computer, and then reconnect it. This should restore
communication, and the LED should turn back on.

Allow the USB-1408FS to operate for at least 30 minutes before using the device. This warm up time is
required to achieve the specified rated accuracy of measurements.

Calibrating the USB-1408FS

The USB-1408FS is shipped fully calibrated. Calibration coefficients are stored in EEPROM. Return the device
to Measurement Computing Corporation when calibration is required. The normal calibration interval is once
per year.

13

USB

connector / cable

Screw terminal

Pins 21 to 40

Screw terminal

Pins 1 to 20

LED

Chapter 3

Functional Details

Theory of operation - analog input acquisition modes

The USB-1408FS can acquire analog input data in two different modes – software paced and continuous scan.

Software paced mode

In software paced mode, you can acquire one analog sample at a time. You initiate the A/D conversion by
calling a software command. The analog value is converted to digital and returned to the computer. You can
repeat this procedure until you have the total number of samples that you want from one channel.

The maximum throughput sample rate in software paced mode is system-dependent.

Continuous scan mode

In continuous scan mode, you can acquire data from up to eight channels. The analog data is continuously
acquired and converted to digital values until you stop the scan. Data is transferred in blocks of 31 samples from
the USB-1408FS to the memory buffer on your computer.

The maximum continuous scan rate of 48 kS/s is an aggregate rate. The total acquisition rate for all channels
cannot exceed 48 kS/s. You can acquire data from one channel at 48 kS/s, two channels at 24 kS/s, and four
channels at 12 kS/s. You can start a continuous scan with either a software command or with an external
hardware trigger event.

External components

The USB-1408FS has the following external components, as shown in Figure 3.

 USB connector
 LED
 Screw terminal banks (2)

Figure 3. USB-1408FS external components

14

USB-1408FS User's Guide Functional Details

LED Illumination

Indication

Steady green

The USB-1408FS is connected to a computer or external USB hub.

Blinks continuously

Data is being transferred.

USB connector

The USB connector is on the right side of the USB-1408FS. This connector provides +5 V power and
communication. The voltage supplied through the USB connector is system-dependent, and may be less than
5 V. No external power supply is required.

LED

The LED on the front of the housing indicates the communication status of the USB-1408FS. It uses up to 5 mA
of current and cannot be disabled. The table below defines the function of the USB-1408FS LED.

LED Illumination

Screw terminal wiring

The USB-1408FS has two rows of screw terminals—one row on the top edge of the housing, and one row on
the bottom edge. Each row has 20 connections. Pin numbers are identified in Figure 4.

Figure 4. USB-1408FS Screw terminal pin numbers

Screw terminal – pins 1-20

The screw terminals on the top edge of the USB-1408FS (pins 1 to 20) provide the following connections:

 Eight analog input connections (CH0 IN to CH7 IN)
 Two analog output connections (D/A OUT 0 to D/A OUT 1)
 One external trigger source (TRIG_IN)
 One SYNC terminal for external clocking and multi-unit synchronization (SYNC)
 One voltage output source (2.5VREF)
 Five analog ground connections (AGND)
 One ground connection (GND)
 One external event counter connection (CTR)

15

USB-1408FS User's Guide Functional Details

Connector type

Screw terminal

Wire gauge range

16 AWG to 30 AWG

20 CTR

19 SYNC

18 TRIG IN

17 GND

16 +2.5VREF1514 D/A OUT 1

13 D/A OUT 01211109

8

AGND

AGND

CH7 IN

CH6 IN

AGND

CH5 IN

7 CH4 IN

6 AGND

5 CH3 IN

4 CH2 IN

3 AGND

2 CH1 IN

1 CH0 IN

GND 40

GND 31

PC +5 V 30

GND 29

Port A7 28

Port B7 39

Port B6 38

Port B5 37

Port B4 36

Port B3 35

Port B2 34

Port B1 33

Port B0 32

Port A6 27

Port A5 26

Port A4 25

Port A3 24

Port A2 23

Port A1 22

Port A0 21

8-channel single-ended mode pin out

20 CTR

19 SYNC

18 TRIG_IN

17 GND

16 +2.5VREF1514 D/A OUT 1

13 D/A OUT 01211109

8

AGND

AGND

CH3 IN LO

CH3 IN HI

AGND

CH2 IN LO

7 CH2 IN HI

6 AGND

5 CH1 IN LO

4 CH1 IN HI

3 AGND

2 CH0 IN LO

1 CH0 IN HI

GND 40

GND 31

PC +5 V 30

GND 29

Port A7 28

Port B7 39

Port B6 38

Port B5 37

Port B4 36

Port B3 35

Port B2 34

Port B1 33

Port B0 32

Port A6 27

Port A5 26

Port A4 25

Port A3 24

Port A2 23

Port A1 22

Port A0 21

4-channel differential mode pin out

Screw terminal – pins 21-40

The screw terminals on the bottom edge of the (pins 21 to 40) provide the following connections:

 16 digital I/O connections (PortA0 to Port A7, and Port B0 to Port B7)
 One power connection (PC+5 V)
 Three ground connections (GND)

Main connector and pin out

Analog input terminals (CH0 IN - CH7 IN)

You can connect up to eight analog input connections to the screw terminal containing pins 1 to 20 (CH0 IN
through CH7 IN.) Refer to the "Main connector and pin out" diagrams above for the location of these pins.

You can configure the analog input channels as eight single-ended channels or four differential channels. When

configured for differential mode, each analog input has 14-bit resolution. When configured for single-ended
mode, each analog input has 13-bit resolution, due to restrictions imposed by the A/D converter.

Single-ended configuration

When all of the analog input channels are configured for single-ended input mode, eight analog channels are
available. The input signal is referenced to signal ground (GND), and delivered through two wires:

 The wire carrying the signal to be measured connects to CH# IN.
 The second wire connects to AGND.

The input range for single-ended mode is ±10 V. No other ranges are supported in this mode. Figure 5
illustrates a typical single-ended measurement connection.

16

USB-1408FS User's Guide Functional Details

Pin 3

AGND

Pin 1

CH0

Figure 5. Single-ended measurement connection

Battery voltage should read as expected when the hardware is configured for single-ended mode.

Single-ended measurements using differential channels

To perform a single-ended measurement using differential channels, connect the signal to "CHn IN HI" input,
and ground the associated "CHn IN LO" input.

Differential configuration

When all of the analog input channels are configured for differential input mode, four analog channels are
available. In differential mode, the input signal is measured with respect to the low input.

The input signal is delivered through three wires:
 The wire carrying the signal to be measured connects to CH0 IN HI, CH1 IN HI, CH2 IN HI, or CH3 IN

HI.

 The wire carrying the reference signal connects to CH0 IN LO, CH1 IN LO, CH2 IN LO, or CH3 IN LO.
 The third wire connects to GND.

A low-noise precision programmable gain amplifier (PGA) is available on differential channels to provide gains
of up to 20 and a dynamic range of up to 14-bits. Differential mode input voltage ranges are ±20 V, ±10 V,
±5 V, ±4 V, ±2.5 V, ±2.0 V, ±1.25 V, and ±1.0 V.

In differential mode, the following two requirements must be met for linear operation:

 Any analog input must remain in the −10V to +20V range with respect to ground at all times.
 The maximum differential voltage on any given analog input pair must remain within the selected voltage

range.

The input [common-mode voltage + signal] of the differential channel must be in the

−10 V to +20 V range in order to yield a useful result. For example, you input a 4 V pp sine wave to CHHI, and
apply the same sine wave 180° out of phase to CHLO. The common mode voltage is 0 V. The differential input
voltage swings from 4 V− (−4 V) = 8 V to (−4 V) − 4 V = −8V. Both inputs satisfy the

−10 V to +20 V input range requirement, and the differential voltage is suited for the ±10 V input range (see
Figure 6).

17

USB-1408FS User's Guide Functional Details

+4V

-4V

+4V

-4V

0V

CHLO

CHHI

+/-8V

8V Differential

Measured Signal

+11V

+7V

+11V

+/-8V

+15V

8V Differential

CHLO

CHHI

Measured Signal

-3V

-11V

-7V

+/-7V

8V Differential

-11V

-7V

-3V

3V

CHLO

CHHI

Measured Signal

Figure 6. Differential voltage example: common mode voltage of 0 V

If you increase the common mode voltage to 11 V, the differential remains at ±8 V. Although the [common­mode voltage + signal] on each input now has a range of +7 V to +15 V, both inputs still satisfy the −10 V to

+20 V input requirement (see Figure 7).

Figure 7. Differential voltage example: common mode voltage of 11 V

If you decrease the common-mode voltage to −7 V, the differential stays at ±8 V. However, the solution now
violates the input range condition of −10 V to +20 V. The voltage on each analog input now swings from −3V
to −11V. Voltages between −10 V and −3 V are resolved, but those below -10 V are clipped (see Figure 8).

Figure 8. Differential voltage example: common mode voltage of -7 V

Since the analog inputs are restricted to a −10 V to +20 V signal swing with respect to ground, all ranges except
±20V can realize a linear output for any differential signal with zero common mode voltage and full scale signal
inputs. The ±20 V range is the exception. You cannot put −20 V on CHHI and 0 V on CHLO since this violates
the input range criteria. The following table shows some possible inputs and the expected results.

18

USB-1408FS User's Guide Functional Details

CHHI

CHLO

Result

−20 V

0 V

In Valid

−15 V

+5 V

In Valid

−10 V

0 V

−10 V

−10 V

+10 V

−20 V

0 V

+10 V

−10 V

0 V

+20 V

−20 V

+10 V

−10 V

+20 V

+10 V

0 V

+10 V

+15 V

−5 V

+20 V

+20 V

0

+20 V

Pin 21
PORT A0

Pin 30
PC +5V

Pin 40
GND

Sample inputs and differential results

For more information on analog signal connections

For more information on single-ended and differential inputs, refer to the Guide to Signal Connections (this
document is available on our web site at www.mccdaq.com/signals/signals.pdf)

Analog output terminals (D/A OUT 0 and D/A OUT 1)

You can connect up to two analog output connections to the screw terminal pins 13 and 14 (D/A OUT 0 and D/A

OUT 1). Refer to the "Main connector and pin out" diagrams on page 16 for the location of these pins.

Each channel can be paced individually at rates up to 10,000 updates per second. Both channels can be paced
simultaneously using the same time base at 5000 updates per channel. The 0-4.096 V output range provides a
convenient 1 mV per LSB when setting the output voltage levels.

Digital I/O terminals (Port A0 to A7, and Port B0 to B7)

You can connect up to 16 digital I/O lines to the screw terminal containing pins 21 to 40 (Port A0 to Port A7,
and Port B0 to Port B7.) Refer to the "Main connector and pin out" diagrams on page 16 for the location of
these pins. You can configure each digital port for either input or output.

When you configure the digital bits for input, you can use the digital I/O terminals to detect the state of any
TTL level input. Refer to the switch shown in Figure 9 and the schematic shown in Figure 10. If the switch is
set to the +5 V input, Port A0 reads TRUE (1). If you move the switch to GND, Port A0 reads FALSE.

Figure 9. Digital connection Port A0 detecting the state of a switch

19

USB-1408FS User's Guide Functional Details

+5V+GND

Port A0

Figure 10. Schematic showing switch detection by digital channel Port A0

For more information on digital signal connections

For more information on digital signal connections and digital I/O techniques, refer to the Guide to Signal
Connections (available on our web site at www.mccdaq.com/signals/signals.pdf).

Power terminals

The PC +5V connection (pin 30) draws power from the USB connector. This terminal is a 5 V output that is
supplied by the host computer. Refer to the "Main connector and pin out" diagrams on page 16 for the location
of this pin.

Caution! The +5 V terminal is an output. Do not connect to an external power supply or you may damage

the USB-1408FS and possibly the computer.

The maximum total output current that can be drawn from all USB-1408FS connections (power, analog and
digital outputs) is 420 mA. This maximum applies to most personal computers and self-powered USB hubs.
Bus-powered hubs and notebook computers may limit the maximum available output current to 100 mA.

Just connecting the USB-1408FS to your computer draws 80 mA of current from the USB +5 V supply. Once
you start running applications with the USB-1408FS, each DIO bit can draw up to 2.5 mA, and each analog
output can draw 15 mA. The maximum amount of +5 V current available for experimental use, over and above
that required by the USB-1408FS, is the difference between the total current requirement of the USB (based on
the application), and the allowed current draw of the PC platform (500 mA for desktop PCs and self-powered
hubs, or 100 mA for bus-powered hubs and notebook computers). With all outputs at their maximum output
current, you can calculate the total current requirement of the USB-1408FS USB +5 V supply as follows:

(USB-1408FS @ 80 mA) + (16 DIO @ 2.5 mA ea) + (2 AO @ 15 mA ea ) = 150 mA

For an application running on a PC or powered hub, the maximum available excess current is
500 mA − 150 mA = 350 mA. This number is the total maximum available current at the PC +5 V screw
terminals. Measurement Computing highly recommends that you figure in a safety factor of 20% below this
maximum current loading for your applications. A conservative, safe user maximum in this case would be
280 mA.

Since laptop computers typically allow up to 100 mA, the USB-1408FS in a fully-loaded configuration may be
above that allowed by the computer. In this case, you must determine the per-pin loading in the application to
ensure that the maximum loading criteria is met. The per-pin loading is calculated by simply dividing the +5 V
by the load impedance of the pin in question.

External trigger terminal

The TRIG_IN connection (pin 18) can be configured for either rising or falling edge. Refer to the "Main

connector and pin out" diagrams on page 16 for the location of this pin.

Counter terminal

The CTR connection (pin 20) is input to the 32-bit external event. Refer to the "Main connector and pin out"
diagrams on page 16 for the location of this pin. The internal counter increments when the TTL levels transition
from low to high. The counter can count frequencies of up to 1 MHz.

20

USB-1408FS User's Guide Functional Details

Single-ended measurement

Differential measurement

+2.5VREF terminal

The +2.5VREF connection (pin 16) is an output terminal that supplies 2.5 volts. The images below show the
+2.5VREF pin configured as the voltage source for channel 0.

SYNC terminal

The SYNC connection (pin 19) is a bidirectional I/O signal. You can use it for two purposes:
 Configure as an external clock input to externally source the A/D conversions. The SYNC terminal

supports TTL-level input signals of up to 48 kHz.

 Configure as an output to synchronize with a second USB-1408FS and acquire data from 16 channels. For

information on synchronizing multiple units, refer to page 24.

Ground terminals

The four analog ground (AGND) connections provide a common ground for all USB-1408FS input channels.
Four ground (GND) connections provide a common ground for the DIO, TRIG_IN, CTR, SYNC and PC +5V
connections. Refer to the "Main connector and pin out" diagrams on page 16 for the location of these pins.

Accuracy

The overall accuracy of any instrument is limited by the error components within the system. Quite often,
resolution is incorrectly used to quantify the performance of a measurement product. While "14-bits" or "1 part
in 16383" does indicate what can be resolved, it provides little insight into the quality of an absolute
measurement. Accuracy specifications describe the actual results that can be realized with a measurement
device.

There are three types of errors which affect the accuracy of a measurement system:

 offset
 gain
 nonlinearity

The primary error sources in the USB-1408FS are offset and gain. Nonlinearity is small in the USB-1408FS,
and is not significant as an error source with respect to offset and gain.

Figure 11 shows an example of an ideal, error-free, USB-1408FS transfer function. The typical calibrated
accuracy of the USB-1408FS is range-dependent, as explained in the "Specifications" chapter on page 26. We
use a ±10 V range here as an example of what you can expect when performing a measurement in this range.

21

USB-1408FS User's Guide Functional Details

-10V

+10V

Input Voltage

0

16383

Output Code

8192

-10V

+10V

Input Voltage

0

16383

Offset=2.44mV

Ideal

Actual

Output Code

2.44mV

8192

Figure 11. Ideal ADC transfer function

The offset error is measured at mid-scale. Ideally, a zero volt input should produce an output code of 8192. Any
deviation from this is an offset error.

Figure 12 shows an example of a USB-1408FS transfer function with a ±2.44 mV offset error. Offset error
affects all codes equally by shifting the entire transfer function up or down along the input voltage axis.

The accuracy plots in Figure 12 are drawn for clarity and are not drawn to scale.

Figure 12. ADC transfer function with offset error

Gain error is a change in the slope of the transfer function from the ideal, and is typically expressed as a

percentage of full-scale. Figure 13 shows the USB-1408FS transfer function with gain error. Gain error is easily
converted to voltage by multiplying the full-scale (FS) input by the error.

22

USB-1408FS User's Guide Functional Details

-10V

+10V

Input Voltage

0

16383

Actual

Ideal

Output Code

Gain error = +0.02% or +2 mV
Gain error = -0.02%, or -2 mV

8192

-10V

+10V

Input Voltage

0

16383

2.44 mV

8192

Output Code

Ideal

Ideal +2.44 mV + 2 mV

Ideal -(2.44 mV + 2 mV)

Ideal -(2.44 mV + 2 mV)

Ideal

Ideal +2.44 mV + 2 mV

The accuracy plots in Figure 13 are drawn for clarity and are not drawn to scale.

Figure 13. ADC Transfer function with gain error

Figure 13 shows an example of a USB-1408FS transfer function with a calibrated gain error of ±0.02%, or
±2 mV. This means that at full scale, neglecting the effect of offset for the moment, the measurement would be
within 2 mV of the actual value. Note that gain error is expressed as a ratio. Values near ±FS are more affected
from an absolute voltage standpoint than are values near mid-scale, which see little or no voltage error.

Combining these two error sources in Figure 14, we have a plot of the error band of the USB-1408FS for the
±10 V range. This is a graphical version of the typical accuracy specification of the product.

The accuracy plots in Figure 14 are drawn for clarity and are not drawn to scale

Figure 14. Error band plot

23

USB-1408FS User's Guide Functional Details

Element

Channel

Range

0

CH0

BIP10V

1

CH3

BIP5V

2

CH1

BIP10V

3

CH2

BIP1V

USB-1408FS channel gain queue feature

The USB-1408FS's channel gain queue feature allows you to set up a scan sequence with a unique per-channel
gain setting and channel sequence.

The channel gain queue feature removes the restriction of using an ascending channel sequence at a fixed gain.
This feature creates a channel list which is written to local memory on the USB-1408FS. Each element of the
channel list is made up of a channel number and range setting. An example of a four-element list is shown in the
table below.

Sample channel gain queue list

When a scan begins with the gain queue enabled, the USB-1408FS reads the first element, sets the appropriate
channel number and range, and then acquires a sample. The properties of the next element are then retrieved,
and another sample is acquired. This sequence continues until all elements in the gain queue have been selected.
When the end of the channel list is detected, the sequence returns to the first element in the list.

This sequence repeats until the specified number of samples is gathered. You must carefully match the gain to
the expected voltage range of the associated channel — otherwise, an over range condition can occur. Although
this condition does not damage the USB-1408FS, it does produce a useless full-scale reading. It can also
introduce a long recovery time from saturation, which can affect the next measurement in the queue.

Synchronizing multiple units

You can connect the SYNC pin of two USB-1408FS units together in a master/slave configuration and acquire
data from the analog inputs of both devices using one clock.

By default, the SYNC pin (pin 19) is set for pacer output, and sends the internal pacer A/D clock signal to the
screw terminal. You can use this signal as a clock input to a second USB unit by connecting it to the SYNC pin
of the second USB unit.

When used as a clock input, the SYNC pin operates in one of two modes – Continuous or Gated. The mode is
software-selectable using InstaCal.

 In the default Continuous mode, the USB-1408FS ignores the first clock pulse in order to ensure adequate

setup time.
Use Continuous mode if the unit is being paced from a continuous clock source, such as a generator.

 In the Gated mode, it is assumed that the clock signal will be held off for an adequate amount of time for

setup to occur. No clock pulses are ignored.
Use Gated mode if you want to use the USB-1408FS unit as a slave, and the source of the external clock is

another USB unit.

To synchronize a master USB-1408FS with a slave USB-1408FS and acquire data from the analog inputs of
both devices using one clock, follow the steps below.

1. Connect the SYNC pin of the master USB-1408FS to the SYNC pin of the slave USB-1408FS.

2. Run InstaCal.

3. From the PC Board List on the InstaCal main form, double-click on the USB-1408FS you want to use as a

slave. The Board Configuration dialog opens.

24

USB-1408FS User's Guide Functional Details

Slave

PMD-1608FS

Master

USB-1408FS

Slave

USB-1408FS

SYNC pin

pin 19

For the slave USB-1408FS,
Set the Universal Library option
with .
This configures the SYNC pin on the slave
unit for input and enables pacing from the
master USB-1408FS.

EXTCLOCK

cbAInScan()/AInScan()

4. Select Gated from the Ext. Clock Type drop-down list.

5. Set the Universal Library EXTCLOCK option with cbAInScan()/AInScan for the slave USB-1408FS to

enable pacing from the master USB device.

This InstaCal option does not affect internally paced acquisition. It only affects scans that use the EXTCLOCK
option.

An example of a master/slave configuration is shown here.

Figure 15. Configuring for synchronous data acquisition

When you are operating one USB-1408FS, do not set the EXTCLOCK option unless you are using an external
clock for A/D pacing.

25

Parameter

Conditions

Specification

A/D converter type

Successive approximation type

Input voltage range for linear operation, single-ended
mode

CHx to GND

±10 volts (V) max

Input common-mode voltage range for linear operation,
differential mode

CHx to GND

–10 V min, +20 V max

Absolute maximum input voltage

CHx to GND

±28 V max

Input impedance

122K Ohms

Input current (Note 1)

Vin = +10 V

70 microamperes (µA) typ

Vin = 0 V

–12 µA typ

Vin = –10 V

–94 µA typ

Number of channels

8 single-ended / 4 differential, software
selectable

Input ranges, single-ended mode

±10 V, G=2

Input ranges, differential mode

±20 V, G=1
±10 V, G=2
±5 V, G=4
±4 V, G=5
±2.5 V, G=8
±2.0 V, G=10
±1.25 V, G=16
±1.0 V, G=20
Software selectable

Throughput (Note 2)
Software paced

250 samples per second (S/s) typ,
PC-dependent

Continuous scan

48 kilosamples per second (kS/s)

Channel gain queue

Up to 16
elements

Software configurable channel, range,
and gain.

Resolution (Note 3)
Differential

14-bits, no missing codes

Single-ended

13-bits

Integral linearity error

±2 least significant bit (LSB) typ

Differential linearity error

±0.5 LSB typ

Absolute accuracy long term drift
(Note 4)
±20V range

±3LSB typ. (delta t = 1000 hrs)

±4V range

±6LSB typ. (delta t = 1000 hrs)

±1V range

±8LSB typ. (delta t = 1000 hrs)

2.5VREF accuracy (pin 16)

±36.25 mV max.

2.5VREF output current (pin 16)
Source

5 mA max.

Sink

20 µA min, 100 µA typ

Trigger source

Software
selectable

External digital: TRIG_IN

Specifications

Typical for 25°C unless otherwise specified.
Specifications in italic text are guaranteed by design.

Analog input

Table 1. Analog input specifications

Chapter 4

Note 1: Input current is a function of applied voltage on the analog input channels. For a given input

voltage, Vin, the input leakage is approximately equal to (8.181*Vin-12) µA.

26

USB-1408FS User's Guide Specifications

Range

Absolute Accuracy 25°C (±mV)

Absolute Accuracy 0 to 50°C (±mV)

±20 V

10.98

49.08

±10 V

7.32

33.42

±5 V

3.66

20.76

±4 V

2.92

19.02

±2.5 V

1.83

14.97

±2 V

1.70

14.29

±1.25 V

1.21

12.18

±1 V

1.09

11.63

Range

Absolute Accuracy 25°C (±mV)

Absolute Accuracy 0 to 50°C (±mV)

±10 V

10.98

49.08

Range

Typical counts

Least significant bit

root mean square

(LSB

rms)

±20 V

8

1.21

±10 V

8

1.21

±5 V

9

1.36

±4 V

10

1.51

±2.5 V

12

1.81

±2 V

14

2.12

±1.25 V

18

2.72

±1 V

22

3.33

Range

Typical Counts

LSB

rms

±10 V

8.0

1.21

Note 2: Maximum throughput scanning to PC memory is machine dependent. The rates specified are for

Windows XP only. Maximum rates on operating systems that predate XP may be less and must
be determined through testing on your machine

Note 3: The ADS7871 converter only returns 13-bits (0 to 8192 codes) in single-ended mode.
Note 4: Extrapolating the long term drift accuracy specifications will provide the approximate long term

drift of the USB-1408FS intermediate input ranges.

Table 2. Accuracy, differential mode

Table 3. Accuracy, single-ended mode

Table 4. Noise performance, differential mode

Table 5. Noise performance, single-ended mode

27

USB-1408FS User's Guide Specifications

Parameter

Conditions

Specification

Resolution

12-bits, 1 in 4096

Output range

0 to 4.096 V, 1 mV per LSB.

Number of channels

2

Throughput (Note 5)

Software paced

250 S/s single channel typical, PC dependent

Single channel, continuous scan

10 kS/s

Dual channel, continuous scan,
simultaneous update

5 kS/s
Power on and reset voltage

0V, ±20 mV typ. (initializes to 000h code)

Output drive

Each D/A OUT

±15 mA

Slew rate

0.8 V/microsecond (µs) typ

Range

Accuracy (±LSB)

0 to 4.096 V

4.0 typ, 45.0 max

Range

% of FSR (±)

Gain Error at FS (±mV)

Offset (±mV)

(Note 6)

Accuracy at FS (±mV)

0 to 4.096 V

0.1 typ, 0.9 max

4.0 typ, 36.0 max

1.0 typ, 9.0 max

4.0 typ, 45.0 max

Digital type

CMOS

Number of I/O

16 (Port A0 through A7, Port B0 through B7)

Configuration

2 banks of 8

Pull-up/pull-down
configuration

All pins pulled up to Vs via 47 K resistors (default). Positions available for pull-down to
ground. Hardware selectable via zero ohm (Ω) resistors as a factory option.

Input high voltage

2.0 V min, 5.5 V absolute max

Input low voltage

0.8 V max, –0.5 V absolute min

Output high voltage
(IOH = –2.5 mA)

3.8 V min

Output low voltage
(IOL = 2.5 mA)

0.7 V max
Power on and reset state

Input

Analog output

Table 6. Analog output specifications

Note 5: Maximum throughput scanning from PC memory is machine dependent. The rates specified are

for Windows XP only. Maximum rates on operating systems that predate XP may be less and
must be determined through testing on your machine.

Table 7. Analog output accuracy

Note 6: Zero-scale offsets may result in a fixed zero-scale error producing a "dead-band” digital input

code region.. In this case, changes in digital input code at values less than 0x040 may not
produce a corresponding change in the output voltage. The USB-1408FS offset error is tested and
specified at code 0x040.

Digital input/output

Table 8. Analog output accuracy components

Table 9. Digital I/O specifications

28

USB-1408FS User's Guide Specifications

Parameter

Conditions

Specification

Trigger source (Note 7)

External digital

TRIG_IN

Trigger mode

Software
selectable

Edge sensitive: user configurable for CMOS compatible rising or
falling edge.

Trigger latency

10 µs max

Trigger pulse width

1 µs min

Input high voltage

4.0 V min, 5.5 V absolute max

Input low voltage

1.0 V max, –0.5 V absolute min

Input leakage current

±1.0 µA

Parameter

Conditions

Specification

Pin name

SYNC

Pin type

Bidirectional

Software selectable direction
Output (default)

Outputs internal A/D pacer clock.

Input

Receives A/D pacer clock from external source.

Input clock rate

48 KHz, maximum

Clock pulse width
Input mode

1 µs min

Output mode

5 µs min

Input leakage current

Input mode

±1.0 µA

Input high voltage

4.0 V min, 5.5 V absolute max

Input low voltage

1.0 V max, –0.5 V absolute min

Output high voltage (Note 8)
IOH = –2.5 mA

3.3 V min

No load

3.8 V min

Output low voltage (Note 8)
IOL = 2.5 mA

1.1 V max

No load

0.6 V max

Pin name (Note 9)

CTR

Counter type

Event counter

Number of channels

1

Input type

TTL, rising edge triggered

Input source

CTR screw terminal

Resolution

32 bits

Schmidt trigger hysteresis

20 mV to 100 mV

Input leakage current

±1 µA

Maximum input frequency

1 MHz

High pulse width

500 ns min

Low pulse width

500 ns min

Input high voltage

4.0 V min, 5.5 V absolute max

Input low voltage

1.0 V max, –0.5 V absolute min

External trigger

Table 10. Digital trigger specifications

Note 7: TRIG_IN is a Schmitt trigger input protected with a 1.5 kilohm (kΩ) series resistor.

External clock input/output

Table 11. External clock I/O specifications

Note 8: SYNC is a Schmitt trigger input and is over-current protected with a 200 Ω series resistor.

Counter section

Note 9: CTR is a Schmitt trigger input protected with a 1.5K Ω series resistor.

Table 12. Counter specifications

29

USB-1408FS User's Guide Specifications

EEPROM

1,024 bytes

EEPROM Configuration

Address Range

Access

Description

0x000-0x1FF

Read/write

512 bytes user area

0x200-0x3FF

Read/write with unlock

512 bytes calibration data

Type

High performance 8-bit RISC microcontroller

Program memory

16,384 words

Data memory

2,048 bytes

Parameter

Conditions

Specification

Supply current (Note 10)

80 mA

+5V USB power available
(Note 11)

Connected to self-powered hub
Connected to externally-powered root port hub

4.5 V min, 5.25 V max
Connected to bus-powered hub

4.1 V min, 5.25 V max

Output current (Note 12)
Connected to self-powered hub
Connected to externally-powered root port hub

420 mA max
Connected to bus-powered hub

20 mA max

Parameter

Conditions

Specification

Device type

USB 2.0 full speed

Device compatibility

USB 1.1, USB 2.0

Non-volatile memory

Table 13. Non-volatile memory specifications

Microcontroller

Table 14. Microcontroller specifications

Power

Table 15. Power specifications

Note 10: This is the total current requirement for the USB-1408FS which includes up to 10 mA for the

Note 11: Self-powered hub refers to a USB hub with an external power supply. Self-powered hubs allow a

Note 12: Output current refers to the total amount of current that can be sourced from the USB +5 V,

General

status LED.

connected USB device to draw up to 500 mA.

Root port hubs reside in the PC’s USB host controller. The USB port(s) on your PC are root port
hubs. All externally powered root port hubs (desktop PCs) provide up to 500 mA of current for a
USB device. Battery-powered root port hubs provide 100 mA or 500 mA, depending upon the
manufacturer. A laptop PC that is not connected to an external power adapter is an example of a
battery-powered root port hub.

Bus powered hubs receive power from a self-powered or root port hub. In this case the maximum
current available from the USB +5 V is 100 mA. The minimum USB +5 V voltage level can be
as low as 4.1 V.

analog outputs and digital outputs.

Table 16. General specifications

30

USB-1408FS User's Guide Specifications

Operating temperature range

0 to 70 °C

Storage temperature range

–40 to 70 °C

Humidity

0 to 90% non-condensing

Dimensions

79 millimeters (mm) long x 82 mm wide x 25 mm high

USB cable length

3 meters max

User connection length

3 meters max

Connector type

Screw terminal

Wire gauge range

16 AWG to 30 AWG

Pin

Signal Name

Pin

Signal Name

1

CH0 IN HI

21

Port A0

2

CH0 IN LO

22

Port A1

3

AGND

23

Port A2

4

CH1 IN HI

24

Port A3

5

CH1 IN LO

25

Port A4

6

AGND

26

Port A5

7

CH2 IN HI

27

Port A6

8

CH2 IN LO

28

Port A7

9

AGND

29

GND

10

CH3 IN HI

30

PC+5V

11

CH3 IN LO

31

GND

12

AGND

32

Port B0

13

D/A OUT 0

33

Port B1

14

D/A OUT 1

34

Port B2

15

AGND

35

Port B3

16

+2.5VREF

36

Port B4

17

GND

37

Port B5

18

TRIG_IN

38

Port B6

19

SYNC

39

Port B7

20

CTR

40

GND

Environmental

Table 17. Environmental specifications

Mechanical

Table 18. Mechanical specifications

Main connector and pin out

Table 19. Main connector specifications

4-channel differential mode

31

USB-1408FS User's Guide Specifications

Pin

Signal Name

Pin

Signal Name

1

CH0 IN

21

Port A0

2

CH1 IN

22

Port A1

3

AGND

23

Port A2

4

CH2 IN

24

Port A3

5

CH3 IN

25

Port A4

6

AGND

26

Port A5

7

CH4 IN

27

Port A6

8

CH5 IN

28

Port A7

9

AGND

29

GND

10

CH6 IN

30

PC+5V

11

CH7 IN

31

GND

12

AGND

32

Port B0

13

D/A OUT 0

33

Port B1

14

D/A OUT 1

34

Port B2

15

AGND

35

Port B3

16

+2.5VREF

36

Port B4

17

GND

37

Port B5

18

TRIG_IN

38

Port B6

19

SYNC

39

Port B7

20

CTR

40

GND

8-channel single-ended mode

32

Declaration of Conformity

Manufacturer: Measurement Computing Corporation
Address: 10 Commerce Way
Suite 1008
Norton, MA 02766
USA
Category: Electrical equipment for measurement, control and laboratory use.

Measurement Computing Corporation declares under sole responsibility that the product

USB-1408FS

to which this declaration relates is in conformity with the relevant provisions of the following standards or other
documents:

EU EMC Directive 89/336/EEC: Electromagnetic Compatibility, EN 61326 (1997) Amendment 1 (1998)

Emissions: Group 1, Class A
 EN 55011 (1990)/CISPR 11: Radiated and Conducted emissions.
Immunity: EN61326, Annex A

 IEC 61000-4-2 (1995): Electrostatic Discharge immunity, Criteria C.
 IEC 61000-4-3 (1995): Radiated Electromagnetic Field immunity Criteria A.
 IEC 61000-4-8 (1994): Power Frequency Magnetic Field immunity Criteria A.

Declaration of Conformity based on tests conducted by Chomerics Test Services, Woburn, MA 01801, USA in
February, 2006. Test records are outlined in Chomerics Test Report #EMI4445.06.

We hereby declare that the equipment specified conforms to the above Directives and Standards.

Carl Haapaoja, Director of Quality Assurance

Measurement Computing Corporation

10 Commerce Way

Suite 1008

Norton, Massachusetts 02766

[phone]

Fax: [phone]

E-mail: [e-mail]

www.mccdaq.com