Measurement Computing USB-1608G User manual

USB-1608G Series
Multifunction DAQ Devices
USB-1608G
USB-1608GX
USB-1608GX-2AO
Document Revision 2
April 2012
© Copyright 2012
User's Guide

HM USB-1608G-Series.docx
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3
Table of Contents
Preface
About this User's Guide .......................................................................................................................5
What you will learn from this user's guide .........................................................................................................5
Conventions in this user's guide .........................................................................................................................5
Where to find more information.........................................................................................................................5
Chapter 1
Introducing the USB-1608G Series .....................................................................................................6
Functional block diagram...................................................................................................................................7
Chapter 2
Installing a USB-1608G Series Device ................................................................................................8
What comes with your shipment?.......................................................................................................................8
Hardware .......................................................................................................................................................................... 8
Documentation.................................................................................................................................................................. 8
Unpacking...........................................................................................................................................................8
Installing the software ........................................................................................................................................9
DAQFlex .......................................................................................................................................................................... 9
Universal Library and InstaCal......................................................................................................................................... 9
Installing the hardware .......................................................................................................................................9
Calibrating........................................................................................................................................................10
Self-calibration ................................................................................................................................................................10
Factory calibration...........................................................................................................................................................10
Programming and developing applications.......................................................................................................10
Firmware updates .............................................................................................................................................10
Chapter 3
Functional Details ...............................................................................................................................11
Analog input modes..........................................................................................................................................11
Software paced.................................................................................................................................................................11
Hardware paced ...............................................................................................................................................................11
Burst mode........................................................................................................................................................11
External components ........................................................................................................................................12
USB connector.................................................................................................................................................................12
LEDs................................................................................................................................................................................12
Screw terminals................................................................................................................................................................12
Signal connections............................................................................................................................................14
Analog input ....................................................................................................................................................................14
Analog output (USB-1608GX-2AO only).......................................................................................................................15
External clock I/O............................................................................................................................................................15
Digital I/O........................................................................................................................................................................15
Trigger input....................................................................................................................................................................16
Counter input...................................................................................................................................................................17
Timer output ....................................................................................................................................................................17
Power output....................................................................................................................................................................17
Ground.............................................................................................................................................................................17
Mechanical drawings........................................................................................................................................18
Chapter 4
Specifications......................................................................................................................................19
Analog input.....................................................................................................................................................19
Accuracy...........................................................................................................................................................20
Analog input DC voltage measurement accuracy ............................................................................................................20
Noise performance...........................................................................................................................................................20
Settling time.....................................................................................................................................................................20

USB-1608G Series User's Guide
4
Analog output (USB-1608GX-2AO only)........................................................................................................21
Analog input/output calibration........................................................................................................................22
Digital input/output...........................................................................................................................................22
External trigger.................................................................................................................................................22
External clock input/output...............................................................................................................................23
Counter.............................................................................................................................................................23
Timer ................................................................................................................................................................24
Memory ............................................................................................................................................................24
Power................................................................................................................................................................24
USB ..................................................................................................................................................................24
Environmental ..................................................................................................................................................25
Mechanical .......................................................................................................................................................25
Screw terminal connector .................................................................................................................................25
Differential mode pinout..................................................................................................................................................25
Single-ended mode pinout ...............................................................................................................................................26
Declaration of Conformity..................................................................................................................27

5
Preface
About this User's Guide
What you will learn from this user's guide
This user's guide describes the Measurement Computing USB-1608G Series data acquisition devices and lists
device specifications.
Conventions in this user's guide
For more information about …
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.
bold text Bold text is used for the names of objects on a screen, such as buttons, text boxes, and check boxes.
italic text Italic text is used for the names of manuals and help topic titles, and to emphasize a word or phrase.
Where to find more information
Additional information about USB-1608G Series hardware is available on our website at www.mccdaq.com.
You can also contact Measurement Computing Corporation by phone, fax, or email with specific questions.
Phone: [phone] and follow the instructions for reaching Tech Support.
Fax: [phone] to the attention of Tech Support
Email: [e-mail]

6
Chapter 1
Introducing the USB-1608G Series
The USB-1608G Series includes the following devices:
USB-1608G
USB-1608GX
USB-1608GX-2AO
These devices are USB 2.0 high-speed devices that are supported under the following operating systems:
Microsoft Windows 7/Vista/XP (32-bit or 64-bit)
Macintosh (32-bit or 64-bit)
Linux (32-bit or 64-bit)
The USB-1608G Series is compatible with both USB 1.1 and USB 2.0 ports. The speed of the device may be
limited when using a USB 1.1 port due to the difference in transfer rates on the USB 1.1 versions of the
protocol (low-speed and full-speed).
Each USB-1608G Series device provides the following features:
16 single-ended (SE) or eight differential (DIFF) analog input channels
Eight individually configurable digital I/O channels
Two counter channels (32-bit) that count TTL pulses
One timer output channel (32-bit)
Screw terminals for field wiring connections
The USB-1608GX-2AO also provides two analog output channels. You can pace each channel at rates of up to
500 kS/s per second. You can pace both channels simultaneously at rates of up to 250 kS/s.
USB-1608G Series devices are powered by the +5 volt USB supply from your computer, and require no
external power.

USB-1608G Series User's Guide Introducing the USB-1608G Series
7
Functional block diagram
USB-1608G Series functions are illustrated in the block diagram shown here.
Figure 1. USB-1608G Series functional block diagram

8
Chapter 2
Installing a USB-1608G Series Device
What comes with your shipment?
Verify that the following hardware components are included in the shipment:
Hardware
USB-1608G Series device —USB-1608G, USB-1608GX, or USB-1608GX-2AO (shown below)
USB cable (2 meter length)
Documentation
In addition to this hardware user's guide, a Quick Start Guide booklet is included with the USB-1608G Series
shipment. This booklet provides an overview of the MCC DAQ software you received with the device, and
includes information about installing the software.
Unpacking
As with any electronic device, take care while handling to avoid damage from static electricity. Before
removing the USB-1608G Series from its packaging, ground yourself using a wrist strap or touch either the
computer chassis or other grounded object to eliminate any stored static charge.
If the device is damaged, notify Measurement Computing Corporation immediately by phone, fax, or email.
Phone: [phone] and follow the instructions for reaching Tech Support.
Fax: [phone] to the attention of Tech Support
Email: [e-mail]
For international customers, contact your local distributor. Refer to the International Distributors section on our
web site at www.mccdaq.com/International.

USB-1608G Series User's Guide Installing a USB-1608G Series Device
9
Installing the software
Note: Before installing USB-1608G Series hardware, you must install the software you plan to use with the
device.
The USB-1608G Series is supported by DAQFlex software and Universal Library software. You can install
both software packages on your computer. However, you cannot run both software packages simultaneously
with one USB-1608G Series device.
DAQFlex
Install DAQFlex software when you want to develop data acquisition applications that can be deployed across
multiple operating systems and custom embedded systems.
DAQFlex software for each supported operating system is available from the DAQFlex download page at
www.mccdaq.com/DAQFlexDL. Refer to the DAQFlex Software User's Guide at
www.mccdaq.com/pdfs/manuals/DAQFlex%20Software.pdf for instructions about installing DAQFlex
software.
Universal Library and InstaCal
Install Universal Library and InstaCal when you want to develop data acquisition applications using Windows
programming languages.
Universal Library and InstaCal software are included on the CD that ships with the device. Refer to the Quick
Start Guide booklet for instructions about installing Universal Library and InstaCal software.
Installing the hardware
Install the software before you install your device
A driver needed to run the USB-1608G Series device is installed when you install the software. Therefore, you
need to install the software package you plan to use before you install the hardware.
For operation on a Windows operating system, we recommend that you run Windows Update to update your
operating system with the latest USB drivers.
To connect a USB-1608G Series device to your system, turn on your computer and connect the USB cable to an
available USB port on the computer or to an external USB hub connected to the computer. Connect the other
end of the USB cable to the USB connector on the device. No external power is required.
When you connect the device for the first time to a computer running Windows, a Found New Hardware dialog
opens when the operating system detects the device. The dialog closes after the device is installed.
A green Status LED indicates the device status. When the LED is on, the device is powered and ready for
operation. When the LED is off, the device is not powered or did not initialize. Figure 3 on page 12 shows the
location of the Status LED.
Mac OS X
When connecting the device to a computer installed with the Mac OS X operating system, the Status LED does
not turn on until the device is configured with software.
Caution! Do not disconnect any device from the USB bus while the computer is communicating with
USB-1608G Series hardware, or you may lose data and/or your ability to communicate with the
device.
If the Status LED is off
If the Status LED is on but then turns off, the computer has lost communication with the USB-1608G Series
device. To restore communication, disconnect the USB cable from the computer and then reconnect it. This
should restore communication, and the LED should turn on.

USB-1608G Series User's Guide Installing a USB-1608G Series Device
10
Calibrating
Self-calibration
USB-1608G Series hardware supports self-calibration. Calibrate the USB-1608G Series device whenever the
ambient temperature changes by more than ±10 °C from the last self-calibration. Use either InstaCal or the
DAQFlex FlexTest utility to calibrate the device.
Factory calibration
The Measurement Computing Manufacturing Test department performs the initial factory calibration. Contact
Measurement Computing for details about how to return your device and have it calibrated to the factory
specifications.
Programming and developing applications
You can program and develop applications for the USB-1608G Series device using MCC DAQ software and
DAQFlex software. OEM users can create a custom driver for use with the message-based firmware to interface
with the device.
Refer to the Quick Start Guide for information about the Universal Library and InstaCal.
Refer to the DAQFlex Software User's Guide for information about DAQFlex software.
Refer to the Message-based Firmware Specification for information about the message-based firmware.
Firmware updates
Your DAQ device contains firmware that can be updated in the field if required. Firmware is available for
download at www.mccdaq.com/firmware.aspx.We recommend that you check this page periodically to see if an
update to your device firmware is available.

11
Chapter 3
Functional Details
Analog input modes
USB-1608G Series devices can acquire analog input data in two basic modes –software paced and hardware
paced.
Software paced
You can acquire one analog sample at a time in software paced mode. You initiate the A/D conversion with a
software command. The analog value is converted to digital data and returned to the computer. Repeat this
procedure until you have the total number of samples that you want.
The sample rate in software paced mode is system-dependent and can range from 33 S/s to 4000 S/s.
Hardware paced
You can acquire data from up to 16 channels in hardware paced mode. The analog data is continuously
acquired, converted to digital values, and written into the FIFO buffer on the device until you stop the scan. The
FIFO buffer is serviced in blocks as the data is transferred from the FIFO buffer to the computer memory
buffer. You start a continuous scan with either a software command or with an external hardware trigger event.
The maximum sampling rate in hardware paced mode from one to 16 channels is 500 kS/s aggregate for the
USB-1608GX and USB-1608GX-2AO, and 250 kS/s for the USB-1608G.
Burst mode
When using the onboard pacer, you can enable burst mode for more precise timing between samples. When
burst mode is enabled, each successive channel in a scan is sampled at the maximum A/D rate. This ensures that
samples from each channel are taken as close as possible to the same absolute point in time. When burst mode
is disabled, data is sampled at evenly spaced intervals, allowing maximum settling time and best amplitude
accuracy. Multi-channel scanning with burst mode enabled and disabled is shown in Figure 2.
Figure 2. Multi-channel scan with burst mode enabled and disabled
The burst mode sample period is 2 µs on the USB-1608GX and USB-1608GX-2AO, and 4 µs on the
USB-1608G.
You can trigger the acquisition with the external trigger, and control the clock period with the internal or
external A/D pacer clock. Pacing from the external clock always operates with burst mode enabled.

USB-1608G Series User's Guide Functional Details
12
External components
USB-1608G Series devices have the following external components (see Figure 3):
USB connector
LEDs
Screw terminals
Figure 3. USB-1608G Series device external components
USB connector
The USB connector provides +5 V power and communication. No external power supply is required.
LEDs
USB-1608G Series devices have two LEDs –Status and Activity.
The Status LED turns on when the device is detected and installed on the computer.
The Activity LED blinks when data is transferred, and is off otherwise.
Figure 3 shows the location of each LED.
Screw terminals
The USB-1608G Series device screw terminals provide the following connections:
16 SE (CH0 to CH15) or eight DIFF (CH0H/CH0L to CH7H/CH7L) analog input connections
Eight digital I/O connections (DIO0 to DIO7)
Two analog output connections (AOUT0, AOUT1) –USB-1608GX-2AO only
One external clock input (AICKI) and one external clock output (AICKO) for analog inputs
One external clock input (AOCKI) and one external clock output (AOCKO) for analog outputs
–USB-1608GX-2AO only
One digital trigger input (TRIG)
Two counter inputs (CTR0, CTR1)
One timer output (TMR)
One power output (+5V)
13 analog ground (AGND) and five digital ground (GND) connections
SE pinout locations are shown in Figure 4. Diff pinout locations are shown in Figure 5.

USB-1608G Series User's Guide Functional Details
13
Figure 4. SE mode pinout
* USB-1608GX-2AO only. "NC" (no connection) on the USB-1608G and USB-1608GX.
Do not connect anything to pins labeled "NC".
Figure 5. DIFF mode pinout
* USB-1608GX-2AO only. "NC" (no connection) on the USB-1608G and USB-1608GX.
Do not connect anything to pins labeled "NC".

USB-1608G Series User's Guide Functional Details
14
Signal connections
Analog input
You can configure the analog inputs for SE or DIFF mode. The input voltage range is software selectable for
±10 V, ±5 V, ±2 V, or ±1 V.
With SE mode, connect up to 16 inputs to screw terminals CH0 to CH15. SE mode requires two wires:
Connect one wire to the signal you want to measure (CHx).
Connect one wire to the analog ground reference (AGND).
Refer to Figure 4 on page 13 for the location of the SE inputs.
With DIFF mode, connect up to eight differential inputs to screw terminals CH0H/CH0L to CH7H/CH7L.
DIFF mode requires two wires plus a ground reference:
Connect one wire to the high/positive signal (CHxH).
Connect one wire to the low/negative signal (CHxL).
Connect one wire to the analog ground reference (AGND).
Refer to Figure 5 on page 13 for the location of the DIFF inputs.
Floating voltage source
When connecting DIFF voltage inputs to a "floating" voltage source, make sure the DIFF input channel has a
DC return path to ground. To create this path, connect a resistor from each low channel input to an AGND pin.
A value of approximately 100 kΩ can be used for most applications.
Leave unused input channels either floating or tied to an AGND terminal. Source impedances should be kept as
small as possible to avoid settling time and accuracy errors.
Figure 6 shows DIFF channels 0-3 connected to a ground path resistor.
Figure 6. DIFF connections with ground path resistor
Channel-Gain queue
The USB-1608G Series channel-gain queue feature allows you to configure a list of channels, modes, and gains
for each scan. The settings are stored in a channel-gain queue list that is written to local memory on the device.
The channel-gain queue list contains one or more channel numbers, modes, and range settings. You can
configure up to 16 elements. The channels can be listed in any order, and can include duplicate channels for
sampling at different ranges.

USB-1608G Series User's Guide Functional Details
15
An example of a 4-element list is shown in the table below.
Sample channel gain queue list
Element
Channel
Range
Mode
0
CH5
BIP5V
SE
1
CH1
BIP10V
DIFF
2
CH15
BIP1V
SE
3
CH5
BIP5V
SE
Carefully match the gain to the expected voltage range on the associated channel or an over range condition
may occur. Although this condition does not damage the device, it does produce a useless full-scale reading,
and can introduce a long recovery time due to saturation of the input channel.
For more information about analog signal connections
For more information about analog input connections, refer to the Guide to Signal Connections (this document
is available on our web site at www.mccdaq.com/signals/signals.pdf).
Analog output (USB-1608GX-2AO only)
The USB-1608GX-2AO has two 16-bit analog outputs (AOUT0 and AOUT1). Both outputs can be updated
simultaneously at a rate of 250 kS/s per channel. One output can be updated at a rate of 500 kS/s. The output
range is fixed at ±10 V. The outputs default to 0 V when the host computer is shut down or suspended, or when
a reset command is issued to the device.
External clock I/O
USB-1608G Series devices provide one external clock input (AICKI) and one external clock output (AICKO) for
analog inputs.
The USB-1608GX-2AO also has one external clock input (AOCKI) and one external clock output (AOCKO) for
analog outputs.
You can connect an external clock signal to AICKI and/or AOCKI.
When using an external clock, AICKOoutputs the pulse generated from AICKI.
When using a USB-1608GX-2AO, the AOCKOpin outputs the pulse generated from AOCKI.
When using the internal clock, AICKO outputs the ADC scan clock.
When using a USB-1608GX-2AO, AOCKOoutputs the DAC scan clock.
Digital I/O
You can connect up to eight digital I/O lines to DIO0 through DIO7. Each digital channel is individually
configurable for input or output. The digital I/O terminals can detect the state of any TTL-level input. Refer to
the schematic shown in Figure 7.
Figure 7. Schematic showing switch detection by digital channel DIO0
If you set the switch to the +5 V input, DIO0 reads TRUE (1). If you move the switch to GND, DIO0 reads
FALSE (0).

USB-1608G Series User's Guide Functional Details
16
Internal pull-up/down configuration
Unconnected inputs are pulled low by default to 0 V through 47 kΩ resistors via jumper W1 on the circuit
board. The pull-up/pull-down voltage is common to all 47 kΩ resistors. Complete the following steps to
configure these inputs to pull high (+5V).
Caution! The discharge of static electricity can damage some electronic components. Before removing the
USB-1608G Series device from its housing, ground yourself using a wrist strap or touch the
computer chassis or other grounded object to eliminate any stored static charge.
1. Turn the device over and rest the top of the housing on a flat, stable surface.
2. Peel off the four rubber feet on the bottom of the device to access the screws.
3. Remove the four screws from the bottom of the device.
4. Hold both the top and bottom sections together, turn the device over and rest it on the surface, then
carefully remove the top section of the case to expose the circuit board.
5. Configure jumper W1 for either pull-up or pull-down. The jumper is configured by default for pull-down.
Figure 8 shows the location of the jumper on the board.
Figure 8. W1 jumper location
Figure 9 shows the jumper configured for pull-up and pull-down.
Figure 9. W1 jumper configurations
6. Replace the top section of the case, and fasten it to the bottom section with the four screws. Replace the
rubber feet onto each screw.
For more information about digital signal connections
For general information about 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).
Trigger input
The TRIG terminal is an external digital trigger input. The trigger mode is software selectable for edge or level
sensitive.
Edge sensitive mode is configurable for rising or falling edge.
Level sensitive mode is configurable for high or low level.
The default setting at power up is edge sensitive, rising edge.
Retrigger mode
Retrigger mode lets you set up repetitive analog input or output trigger events. The trigger is automatically re-
armed after it is activated. Use software to set the A/D or D/A trigger count (the number of samples you want
per trigger).

USB-1608G Series User's Guide Functional Details
17
Counter input
The CTR0 and CTR1 terminals are 32-bit event counters that can accept frequency inputs up to 20 MHz. The
internal counter increments when the TTL levels transition from low to high.
Timer output
The TMR terminal is a pulse width modulation (PWM) timer output that can generate a pulse output with a
programmable frequency in the range of 0.0149 Hz to 32 MHz. The timer output parameters are software
selectable. Figure 10 shows the timer output schematic.
Figure 10. Timer output schematic
Power output
The +5V terminal can output up to 10 mA maximum. You can use this terminal to supply power to external
devices or circuitry.
Caution! The +5V terminal is an output. Do not connect to an external power supply or you may damage the
device and possibly the computer.
Ground
The analog ground (AGND) terminals provide a common ground for all analog channels.
The digital ground (GND) terminals provide a common ground for the digital, counter, timer, and clock
channels and the power terminal.

USB-1608G Series User's Guide Functional Details
18
Mechanical drawings
Figure 11. USB-1608G Series device circuit board (top) and enclosure dimensions

19
Chapter 4
Specifications
All specifications are subject to change without notice.
Typical for 25 °C unless otherwise specified.
Specifications in italic text are guaranteed by design.
Analog input
Table 1. General analog input specifications
Parameter
Condition
Specification
A/D converter type
Successive approximation
ADC resolution
16 bits
Number of channels
8 differential, 16 single-ended
Software-selectable
Input voltage range
±10 V, ±5 V, ±2 V, ±1 V
Software-selectable per channel
Absolute max input voltage
CHx relative to AGND
±25 V max (power on)
±15 V max (power off)
Input impedance
1 GΩ (power on)
820 Ω (power off)
Input bias current
±10 nA
Input bandwidth
All input ranges,
small signal (–3 dB)
USB-1608G: 750 kHz
USB-1608GX: 870 kHz
USB-1608GX-2AO: 870 kHz
Input capacitance
60 pf
Max working voltage (signal
+ common mode)
±10.2 V max relative to AGND
Common mode rejection ratio
(fIN = 60 Hz, all input
ranges)
86 dB
Crosstalk
Adjacent differential mode
channels, DC to 100 kHz
–75 dB
Input coupling
DC
Sampling rate
USB-1608G: 0.0149 Hz to 250 kHz
USB-1608GX: 0.0149 Hz to 500 kHz
USB-1608GX-2AO: 0.0149 Hz to 500 kHz
Software-selectable
Trigger source
TRIG (see External trigger on page 22)
Sample clock source
Internal A/D clock or external A/D clock (AICKI pin)
Burst mode
USB-1608G: 4 µs
USB-1608GX: 2 µs
USB-1608GX-2AO: 2 µs
Software-selectable using the internal A/D clock; always
enabled when using the external clock (AICKI pin).
Throughput
Software paced
33 to 4000 S/s typ, system dependent
Hardware paced
USB-1608G: 250 kS/s max
USB-1608GX: 500 kS/s max
USB-1608GX-2AO: 500 kS/s max
Channel gain queue
Up to 16 elements
Software-selectable range for each channel
Warm-up time
15 minutes min

USB-1608G Series User's Guide Specifications
20
Accuracy
Analog input DC voltage measurement accuracy
Table 2. DC Accuracy components and specifications. All values are (±)
Range
Gain error
(% of reading)
Offset error
(µV)
INL error
(% of range)
Absolute
accuracy at
Full Scale
(µV)
Gain
temperature
coefficient
(% reading/°C)
Offset
temperature
coefficient
(µV/°C)
±10 V
0.024
915
0.0076
4075
0.0014
47
±5 V
0.024
686
0.0076
2266
0.0014
24
±2 V
0.024
336
0.0076
968
0.0014
10
±1 V
0.024
245
0.0076
561
0.0014
5
Noise performance
For the peak-to-peak noise distribution test, a differential input channel is connected to AGND at the input
terminal block, and 32,000 samples are acquired at the maximum rate available at each setting.
Table 3. Noise performance specifications
Range
Counts
LSBrms
±10 V
6
0.91
±5 V
6
0.91
±2 V
7
1.06
±1 V
9
1.36
Settling time
Settling time is defined as the accuracy that can be expected after one conversion when switching from a
channel with a DC input at one extreme of full scale to another channel with a DC input at the other extreme of
full scale. Both input channels are configured for the same input range.
USB-1608GX-2AO, USB-1608GX
Table 4. Input settling time specifications in µS, typical
Range
2 µS settling accuracy
(% FSR)
4 µS settling accuracy
(% FSR)
9 µS settling accuracy
(% FSR)
±10 V
0.1251
0.0031
0.0015
±5 V
0.0687
0.0031
0.0015
±2 V
0.0687
0.0031
0.0015
±1 V
0.0687
0.0031
0.0015
USB-1608G
Table 5. Input settling time specifications in µS, typical
Range
4 µS settling accuracy
(% FSR)
6 µS settling accuracy
(% FSR)
±10 µS settling accuracy
(% FSR)
±10 V
0.0061
0.0031
0.0015
±5 V
0.0061
0.0031
0.0015
±2 V
0.0061
0.0031
0.0015
±1 V
0.0061
0.0031
0.0015