Measurement Computing USB-1608FS User manual

USB-1608FS
Analog Input and Digital I/O
Document Revision 7A
January 2014
© Copyright 2014
User's Guide

HM USB-1608FS
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Notice
Measurement Computing Corporation does not authorize any Measurement Computing Corporation product for
use in life support systems and/or devices without prior written consent from Measurement Computing
Corporation. Life support devices/systems are devices or systems that, a) are intended for surgical implantation
into the body, or b) support or sustain life and whose failure to perform can be reasonably expected to result in
injury. Measurement Computing Corporation products are not designed with the components required, and are
not subject to the testing required to ensure a level of reliability suitable for the treatment and diagnosis of
people.

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-1608FS................................................................................................................6
Functional block diagram...................................................................................................................................6
Chapter 2
Installing the USB-1608FS....................................................................................................................7
What comes with your USB-1608FS shipment? ................................................................................................7
Hardware .......................................................................................................................................................................... 7
Software............................................................................................................................................................................ 7
Documentation.................................................................................................................................................................. 7
Unpacking...........................................................................................................................................................7
Installing the software ........................................................................................................................................7
Installing the hardware .......................................................................................................................................7
Calibrating the hardware.....................................................................................................................................8
Chapter 3
Functional Details .................................................................................................................................9
Analog input acquisition modes .........................................................................................................................9
Software paced.................................................................................................................................................................. 9
Hardware paced ................................................................................................................................................................ 9
BURSTIO......................................................................................................................................................................... 9
External components ........................................................................................................................................10
USB connector.................................................................................................................................................................10
LED .................................................................................................................................................................................10
Screw terminals................................................................................................................................................................10
Signal connections............................................................................................................................................11
Analog input....................................................................................................................................................................11
Channel-Gain queue ........................................................................................................................................................12
Digital I/O........................................................................................................................................................................12
Pull-up/down configuration .............................................................................................................................................12
Counter input...................................................................................................................................................................13
Trigger input....................................................................................................................................................................13
SYNC I/O ........................................................................................................................................................................13
Calibration output............................................................................................................................................................13
Ground.............................................................................................................................................................................14
Power output....................................................................................................................................................................14
Accuracy...........................................................................................................................................................14
Synchronized operations...................................................................................................................................17
Mechanical drawings........................................................................................................................................18
Chapter 4
Specifications......................................................................................................................................19
Analog input.....................................................................................................................................................19
Digital I/O.........................................................................................................................................................20
External trigger.................................................................................................................................................21
External clock input/output...............................................................................................................................21
Counter.............................................................................................................................................................22
Memory ............................................................................................................................................................22

USB-1608FS User's Guide
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Microcontroller.................................................................................................................................................22
Power................................................................................................................................................................23
General .............................................................................................................................................................23
Environmental ..................................................................................................................................................23
Mechanical .......................................................................................................................................................23
Screw terminal connector and pinout ...............................................................................................................23
Declaration of Conformity..................................................................................................................25

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-1608FS data acquisition device and lists device
specifications.
Conventions in this user's guide
For more information
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
For additional information relevant to the operation of your hardware, refer to the Documents subdirectory
where you installed the MCC DAQ software (C:\Program Files\Measurement Computing\DAQ by default), or
search for your device on our website at www.mccdaq.com.

6
Chapter 1
Introducing the USB-1608FS
The USB-1608FS is an analog input and digital I/O data acquisition device providing the following features:
Eight 16-bit single-ended (SE) analog input channels
Each input channel has a dedicated A/D converter for simultaneous sampling.
Software-selectable analog input ranges of ±10 V, ±5 V, ±2 V, and ±1 V
Eight individually configurable digital I/O channels
One 32-bit event counter
One external digital trigger input
Bidirectional external clock for synchronous operations with a second device.
Screw terminals for field wiring connections
The device is powered by the +5V USB supply from the computer, and requires no external power.
The USB-1608FS is a full-speed device that 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).
Functional block diagram
USB-1608FS functions are illustrated in the block diagram shown here.
Figure 1. Functional block diagram

7
Chapter 2
Installing the USB-1608FS
What comes with your USB-1608FS shipment?
The following items are shipped with the USB-1608FS.
Hardware
USB-1608FS
USB cable
Software
MCC DAQ CD
Documentation
In addition to this hardware user's guide, you should also receive the Quick Start Guide. This booklet provides
an overview of the MCC DAQ software you received with the device, and includes information about installing
the software. Please read this booklet completely before installing any software or hardware.
Unpacking
As with any electronic device, take care while handling to avoid damage from static electricity. Before
removing the USB-1608FS 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.
Knowledgebase: kb.mccdaq.com
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.
Installing the software
Refer to the Quick Start Guide for instructions on installing the software on the MCC DAQ CD. This booklet is
available in PDF at www.mccdaq.com/PDFmanuals/DAQ-Software-Quick-Start.pdf.
Installing the hardware
Be sure you are using the latest system software
Before installing the device, run Windows Update to update your operating system with the latest HID and USB
drivers.
To connect the USB-1608FS to your system, 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-1608FS installs as a composite device with separate devices attached. When you connect the device
for the first time, a Found New Hardware dialog opens as each device interface is detected. This is normal.
After the device is installed its LED will blink and then remain on. This indicates that communication is
established between the USB-1608FS and your computer.

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If the LED turns off
If communication is lost between the device and the computer, the device LED turns off. Disconnect the USB
cable from the computer and then reconnect it. This should restore communication, and the LED should turn on.
Calibrating the hardware
You can calibrate the USB-1608FS with InstaCal. Perform calibration whenever the ambient temperature
changes by more than ±10 °C from the last calibration.
The Measurement Computing Manufacturing Test department performs the initial factory calibration. Contact
Measurement Computing if you want to have the factory calibration coefficients restored.

9
Chapter 3
Functional Details
Analog input acquisition modes
The USB-1608FS can acquire analog input data in three modes – software paced, hardware paced, and
BURSTIO.
Software paced
The USB-1608FS acquires data one analog sample at a time using software-paced mode. 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.
The USB-1608FS can attain throughput rates up to 500 S/s using a software loop. This rate is system-
dependent.
Hardware paced
The USB-1608FS can acquire data from up to eight channels simultaneously in hardware-paced mode. The
analog data is acquired, converted to digital values, and written to an onboard FIFO buffer on the USB-1608FS
until you stop the scan. Data is transferred from the USB-1608FS FIFO buffer to the memory buffer on your
computer.
The A/D converter is paced by either an internal or external clock source.
The maximum sample rate is an aggregate rate. The total sample rate for all channels is 100 kS/s divided by the
number of channels, with a maximum rate of 50 kS/s for any channel. Using this equation, the USB-1608FS can
acquire data from one channel at 50 kS/s, two channels at 50 kS/s each, four channels at 25 kS/s each, and so
on, up to eight channels at 12.5 kS/s each. You start a hardware-paced scan with a software command.
Optionally, hardware-paced scans can be delayed by an external hardware trigger event.
BURSTIO
When using BURSTIO, the USB-1608FS can acquire data at higher rates using the full capacity of the
32 kilosample FIFO. The acquired data is then read from the FIFO and transferred to a user buffer in the
computer after the acquisition is complete. You can initiate a single acquisition sequence of one, two, four, or
eight channels with a software command. Optionally, BURSTIO scans can be delayed by an external hardware
trigger event.
When BURSTIO is enabled, the number of samples acquired in a scan is limited to the depth of the onboard
memory. The maximum sample rate in BURSTIO mode is an aggregate rate is 200 kS/s. The maximum sample
rate for all channels is 200 kS/s divided by the number of channels, with a maximum rate of 50 kS/s for any
channel.
The maximum sample rate that you can acquire data using BURSTIO is 50 kS/s each for one, two, or four
channels, and 25 kS/s each for eight channels.

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External components
The external components – screw terminal banks, LED, and USB connector –are shown in Figure 2.
1 Screw terminal pins 21 to 40 3 Screw terminal pins 1 to 20
2 LED 4 USB connector
Figure 2. USB-1608FS components
USB connector
The USB connector provides +5 V power and communication. No external power supply is required.
LED
The LED indicates the communication status; it cannot be disabled. LED states are listed in the table below.
LED behavior
LED state Indication
On – steady green The device is connected to a computer or external USB hub.
Blinks once A USB command is received.
Blinks continuously Data is being transferred.
Blinks three times Initial communication is established between the USB-1608FS and the computer.
Blinks at a slow rate The analog input is configured for external trigger. The LED stops blinking and illuminates
steady green when the trigger is received.
Screw terminals
The screw terminals provide the following connections:
Eight analog inputs (CH0 IN to CH7 IN)
Eight digital I/O lines(DIO0 to DIO7)
One external event counter input (CTR)
One SYNC I/O terminal for external clocking and multi-unit synchronization (SYNC)
One external trigger input (TRIG_IN)
One calibration output (CAL)
One power output (PC +5 V)
analog ground (AGND) and digital ground (GND) connections

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Use 16 AWG to 30 AWG wire when making connections to the screw terminals. Pinout locations are shown in
Figure 3 below.
Figure 3. Screw terminal pinout
Signal connections
Analog input
You can connect up to eight analog input connections to CH0 IN through CH7 IN. Connect unused analog input
terminals to ground terminals during operation. For example, if you are not using terminal 15 (CH7 IN), connect
this terminal to terminal 16 (AGND).
The analog input channels are configured for single-ended input mode. Each analog signal is referenced to
signal ground (AGND), and requires two wires:
Connect the wire carrying the signal to be measured to CH# IN.
Connect the second wire to AGND.
The input voltage ranges are ±10 V, ±5 V, ±2.0 V, ±1.0 V.
For more information on analog signal connections
For more information on single-ended inputs, refer to the Guide to Signal Connections (this document is
available on our web site at www.mccdaq.com/signals/signals.pdf).

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Channel-Gain queue
The channel-gain queue feature allows you to configure a different gain setting for each analog input channel.
The gain settings are stored in a channel-gain queue list that is written to local memory on the device.
The channel-gain queue list must contain all eight channels listed in consecutive order. An example of the
channel-gain queue list is shown in the table below.
Sample channel-gain queue list
Element Channel Range
0 CH0 BIP10V
1 CH1 BIP5V
2 CH2 BIP10V
3 CH3 BIP1V
4 CH4 BIP2V
5 CH5 BIP10V
6 CH6 BIP1V
7 CH7 BIP5V
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.
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. During initial power on or reset the digital pins are set for input.
The digital I/O terminals can detect the state of any TTL-level input. Refer to the schematic shown in Figure 4.
Figure 4. Schematic showing switch detection by digital channel DIO0
If you set the switch to the +5 V input, DIO0 reads TRUE (1). When set to GND, DIO0 reads FALSE (0).
Pull-up/down configuration
Boards designed with hardware revision E and later have a user-configurable internal jumper to configure the
digital bits for pull-up (default) or pull-down. The hardware revision is listed with the part number on the
bottom of the device, for example P/N 193334E.
If the p/n of your board is earlier than hardware revision E, the default configuration is pull-up. To configure for
pull-down, the board must be modified at the factory.
If your board has a user-configurable jumper, complete the following steps to set the pull-up/down
configuration:
1. Unplug the device from the computer.
2. Turn the device over and rest the top of the housing on a flat, stable surface.
Caution! The discharge of static electricity can damage some electronic components. Before removing the
USB-1608FS from its housing, ground yourself using a wrist strap or touch the computer chassis
or other grounded object to eliminate any stored static charge.
3. Remove the three screws from the bottom of the device using a #1 Philips head screwdriver.
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.

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The user-configurable jumper is labeled DIO. Figure 5 shows the location of the jumper on the circuit
board.
Figure 5. Pull-up/down jumper location
5. Configure the jumper for pull-up or pull-down, as shown in Figure 6.
Figure 6. Pull-up/down jumper configuration
6. Replace the top section of the housing, and fasten it to the bottom section with the three screws.
For more information on digital signal connections
For general information regarding 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).
Counter input
The CTR terminal is a 32-bit event counter that can accept frequency inputs up to 1 MHz. The internal counter
increments when the TTL levels transition from low to high.
Trigger input
The TRIG_IN terminal is an external digital trigger input. The trigger mode is set for edge sensitive, and is
configurable for rising or falling edge. On power up and reset the trigger mode is set for rising edge.
SYNC I/O
The SYNC terminal is a bidirectional I/O signal that can be configured as an input (default) or an output.
Configure as an external clock input to externally source the A/D conversions. The SYNC terminal
supports TTL-level input signals of up to 50 kHz.
Configure as an output to pace conversions on a second USB-1608FS device and acquire data from
16 channels. For more information about synchronized operations see page 17.
Calibration output
The CAL terminal is an output that is used to calibrate the USB-1608FS. Do not use this pin for any other
purpose. Calibration is software-controlled by InstaCal.

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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, trigger, counter, sync and power
terminals.
Power output
The PC +5V terminal is a 5 volt output that is supplied by the computer. You can use this terminal to supply
power to external devices or circuitry.
Caution! The PC +5V terminal is an output. Do not connect to an external power supply or you may
damage the USB-1608FS and possibly the computer.
The maximum total output current that can be drawn from all USB-1608FS connections (power, analog, and
digital outputs) is 500 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. Note:
If the current requirement of the device exceeds the current available from the computer, connect to a self-
powered hub or power the computer with an external power adapter.
The USB-1608FS can draw up to 150 mA max of current from the USB +5V supply. When running
applications with the device, each DIO bit can source up to 2.5 mA. With all outputs at their maximum output
current, the total current requirement of the PC +5V terminal is calculated as follows:
Total current requirement = (USB-1608FS @ 150 mA) + (8 DIO @ 2.5 mA ea) = 170 mA
The maximum available excess current is the difference between the allowed current draw of the computer
platform and the total output current requirement of the device. For an application running on a computer or
powered hub, the maximum available excess current is calculated as follows:
Maximum excess current = 500 mA – 170 mA = 330 mA
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 in the 250 mA
to 300 mA range.
Accuracy
The overall accuracy of any instrument is limited by the error components within the system. Resolution is
often used incorrectly to quantify the performance of a measurement product. While "16-bits" or "1 part in
65,536" does indicate what can be resolved, it provides little insight into the quality, or accuracy, of an absolute
measurement. Accuracy specifications describe the actual measurement achievable with a USB-1608FS.
There are three types of errors which affect the accuracy of a measurement system:
 offset
 gain
 nonlinearity
The primary error sources in the USB-1608FS are offset and gain. Nonlinearity is small, and is not significant
as an error source with respect to offset and gain.

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Figure 7 shows an ideal, error-free, USB-1608FS transfer function. The typical calibrated accuracy of the
USB-1608FS is range-dependent, as explained in the "Specifications" chapter. We use a ±10 V range as an
example of what you can expect when performing a measurement in this range.
Figure 7. Ideal ADC transfer function
The USB-1608FS offset error is measured at mid-scale. Ideally, a zero volt input should produce an output code
of 32768. Any deviation from this is an offset error. Figure 8 shows the USB-1608FS transfer function with an
offset error. The typical offset error specification for the USB-1608FS on the ±10 V range is ±1.66 mV. 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 8 are drawn for clarity and are not drawn to scale.
Figure 8. 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 9 shows the USB-1608FS transfer function with gain error. Gain error is easily
converted to voltage by multiplying the full-scale input (±10 V) by the error.
The accuracy plots in Figure 9 are drawn for clarity and are not drawn to scale.

USB-1608FS User's Guide
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Figure 9. ADC Transfer function with gain error
For example, the USB-1608FS exhibits a typical calibrated gain error of ±0.04% on all ranges. For the ±10 V
range, this would yield 10 V × ±0.0002 = ±4 mV. This means that at full scale, neglecting the effect of offset for
the moment, the measurement would be within 4 mV of the actual value. Note that gain error is expressed as a
ratio. Values near ±FS (±10 V) 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 10, we have a plot of the error band of the USB-1608FS at ±full
scale (±10 V). This plot is a graphical version of the typical accuracy specification of the product.
The accuracy plots in Figure 10 are drawn for clarity and are not drawn to scale.
Figure 10. Error band plot

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Synchronized operations
You can run up to two USB-1608FS devices on most computers. You can connect the SYNC pin of two devices
together in a master/slave configuration and acquire data from the analog inputs of both devices using one
clock. When the SYNC pin is configured as an output, the internal A/D pacer clock signal is sent to the screw
terminal. You can output the clock to the SYNC pin of a second device that is configured for A/D pacer input.
Change to SYNC pin setting not implemented until first scan
When you change the setting of the SYNC pin to input or to output using InstaCal, the change does not take
place until you run a scan with a USB-1608FS.
Consequently, if you change the SYNC pin from output to input, the SYNC pin remains an output, and
connections to this pin are connections to an output until the first scan runs. This will not damage the
USB-1608FS.
To update the SYNC pin setting before connecting to the SYNC pin, run the InstaCal analog Scan Test.

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18
Mechanical drawings
Figure 11. 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. Analog input specifications
Parameter Condition Specification
A/D converter type 16-bit successive approximation type
Number of channels 8 single-ended
Input configuration Individual A/D per channel
Sampling method Simultaneous
Absolute maximum input voltage CHx IN to GND ±15 V max
Input impedance 100 MΩ, min
Input ranges Software-selectable ±10 V, ±5 V, ±2 V, ±1 V
Sampling rate Scan to PC memory 0.6 S/s to 50 kS/s, software-selectable
Burst scan to 32 k sample FIFO 20 S/s to 50 kS/s, software- selectable
Throughput Software paced 500 S/s all channels
Hardware paced (Note 1) (100 kS/s) / (# of channels),
50 kS/s max for any channel
BURSTIO ≤ 32,768 total samples
(uses onboard FIFO) (200 kS/s) / (# of channels),
50 kS/s max for any channel
Gain queue Software configurable..
Eight unique, consecutive elements – one gain
element per channel.
Resolution 16 bits
No missing codes 15 bits
Crosstalk Signal DC to 25 kHz –80 dB
CAL output User calibration source 0.625 V, 1.25 V, 2.5 V, 5.0 V,
software-selectable
CAL output accuracy (Note 2) ±0.5% typ, ±1.0% max
CAL current ±5 mA max
Trigger source Software-selectable External digital: TRIG_IN
Note 1: Maximum throughput when scanning in hardware paced mode is machine dependent.
Note 2: Actual values used for calibration are measured and stored in EEPROM.
Table 2. Calibrated absolute accuracy
Range Accuracy (mV)
±10 V 5.66
±5 V 2.98
±2 V 1.31
±1 V 0.68

USB-1608FS User's Guide
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Table 3. Accuracy components - All values are (±)
Range % of Reading Gain error at FS (mV) Offset (mV)
±10 V 0.04 4.00 1.66
±5 V 0.04 2.00 0.98
±2 V 0.04 0.80 0.51
±1 V 0.04 0.40 0.28
Table 4 summarizes the noise performance for the USB-1608FS. Noise distribution is determined by gathering
50 k samples with inputs tied to ground at the user connector. Samples are gathered at the maximum specified
sampling rate of 50 kS/s.
Table 4. Noise performance
Range Typical counts LSBrms
±10 V 10 1.52
±5 V 10 1.52
±2 V 11 1.67
±1 V 14 2.12
Digital I/O
Table 5. Digital I/O specifications
Parameter Specification
Digital type CMOS
Number of I/O 8 (DIO0 through DIO7)
Configuration Independently configured for input or output
Pull-up/pull-down configuration All pins pulled up to 5V via 47 kΩ resistors (default).
Hardware revisions E and later may be changed to pull-down using an internal
user-configurable jumper.
Previous revisions can be configured for pull-down at the factory.
Input high voltage threshold 2.0 V min
Input high voltage limit 5.5 V absolute max
Input low voltage threshold 0.8 V max
Input low voltage limit –0.5 V absolute min
0 V recommended min
Output high voltage
(IOH = –2.5 mA) 3.8 V min
Output low voltage
(IOL = 2.5 mA) 0.44 V max
Power on and reset state Input