USB-1208FS User`s Guide
USB-1208FS
Analog and Digital I/O
User's Guide
Document Revision 7
February 2012
© Copyright 2012
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HM USB-1208FS.docx
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-1208FS................................................................................................................ 6
USB-1208FS block diagram ............................................................................................................................... 6
Connecting a USB-1208FS to your computer is easy ........................................................................................ 7
Chapter 2
Installing the USB-1208FS.................................................................................................................... 8
What comes with your shipment? ....................................................................................................................... 8
Hardware .......................................................................................................................................................................... 8
Software ............................................................................................................................................................................ 8
Documentation .................................................................................................................................................................. 8
Unpacking........................................................................................................................................................... 8
Installing the software ........................................................................................................................................ 8
Installing the hardware ....................................................................................................................................... 8
Chapter 3
Functional Details ................................................................................................................................. 9
Analog input acquisition modes ......................................................................................................................... 9
Software paced mode ........................................................................................................................................................ 9
Hardware paced mode....................................................................................................................................................... 9
External components .......................................................................................................................................... 9
USB connector .................................................................................................................................................................. 9
LED .................................................................................................................................................................................. 9
Screw terminals................................................................................................................................................................10
Signal connections ............................................................................................................................................ 11
Analog input ....................................................................................................................................................................11
Analog output ..................................................................................................................................................................14
Digital I/O ........................................................................................................................................................................14
Counter input ...................................................................................................................................................................15
Trigger input ....................................................................................................................................................................15
SYNC I/O ........................................................................................................................................................................15
Calibration output ............................................................................................................................................................15
Ground .............................................................................................................................................................................15
Power output ....................................................................................................................................................................16
Accuracy ........................................................................................................................................................... 16
Synchronized operations ................................................................................................................................... 18
Mechanical drawings ........................................................................................................................................ 19
Chapter 4
Specifications ......................................................................................................................................20
Analog input ..................................................................................................................................................... 20
Analog output ................................................................................................................................................... 22
Digital I/O ......................................................................................................................................................... 22
External trigger ................................................................................................................................................. 23
External clock input/output............................................................................................................................... 23
Counter ............................................................................................................................................................. 24
Non-volatile memory ........................................................................................................................................ 24
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USB-1208FS User's Guide
Microcontroller ................................................................................................................................................. 24
Power ................................................................................................................................................................ 25
General ............................................................................................................................................................. 25
Environmental .................................................................................................................................................. 25
Mechanical ....................................................................................................................................................... 25
Screw terminal connector ................................................................................................................................. 26
Differential mode pinout ..................................................................................................................................................26
Single-ended mode pinout ...............................................................................................................................................27
Declaration of Conformity ..................................................................................................................28
4
Preface
About this User's Guide
What you will learn from this user's guide
This user's guide describes the Measurement Computing USB-1208FS 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
Additional information about the USB-1208FS 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: 508-946-5100 and follow the instructions for reaching Tech Support
Fax: 508-946-9500 to the attention of Tech Support
Email: [email protected]
5
Chapter 1
Introducing the USB-1208FS
The USB-1208FS is a USB 2.0 full-speed analog input and digital I/O data acquisition device supported under
popular Microsoft® Windows® operating systems. It is designed for USB 1.1 ports, and was tested for full
compatibility with both USB 1.1 and USB 2.0 ports.
The USB-1208FS 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 11-bit single-ended inputs, or four 12-bit
differential inputs. Sixteen digital I/O lines are independently selectable as input or output in two 8-bit ports. A
32-bit counter can count TTL pulses. The counter increments when the TTL levels transition from low to high
(rising-edge). A SYNC (synchronization) input / output line lets you pace the analog input acquisition of one
USB module from the clock output of another.
The USB-1208FS is powered by the +5 volt USB supply from your computer. No external power is required.
All I/O connections are made to the device screw terminals.
USB-1208FS block diagram
USB-1208FS functions are illustrated in the block diagram shown here.
Figure 1. USB-1208FS functional block diagram
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USB-1208FS User's Guide
Introducing the USB-1208FS
Connecting a USB-1208FS to your computer is easy
Installing a data acquisition device has never been easier.





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The USB-1208FS 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-1208FS. No third-party device driver is required.
The USB-1208FS is plug-and-play. There are no jumpers to position, DIP switches to set, or interrupts to
configure.
You can connect the USB-1208FS 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 run up to two USB-1208FS devices on most computers.
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 flow is bidirectional between a computer and peripheral over USB connections.
7
Chapter 2
Installing the USB-1208FS
What comes with your shipment?
The following items are shipped with the USB-1208FS.
Hardware


USB-1208FS
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-1208FS 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: 508-946-5100 and follow the instructions for reaching Tech Support
Fax: 508-946-9500 to the attention of Tech Support
Email: [email protected]
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-1208FS 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-1208FS installs as a composite device with separate devices attached. When you connect the
USB-1208FS 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-1208FS and your computer.
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.
8
Chapter 3
Functional Details
Analog input acquisition modes
The USB-1208FS can acquire analog input data in two different modes – software paced and hardware paced.
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 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.
Hardware paced mode
In hardware paced 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-1208FS to the memory buffer on your computer.
The maximum continuous scan rate of 50 kS/s is an aggregate rate. The total acquisition rate for all channels
cannot exceed 50 kS/s. You can acquire data from one channel at 50 kS/s, two channels at 25 kS/s, and four
channels at 12.5 kS/s. You can start a continuous scan with either a software command or with an external
hardware trigger event.
External components
The USB-1208FS has the following external components, as shown in Figure 2.



USB connector
LED
Screw terminal banks
1
2
Screw terminal pins 21 to 40
LED
3
4
Screw terminal pins 1 to 20
USB connector
Figure 2. External components
USB connector
The USB connector provides +5V 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.
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USB-1208FS User's Guide
Functional Details
LED behavior
LED Illumination
Indication
Steady green
Blinks continuously
The USB-1208FS is connected to a computer or external USB hub.
Data is being transferred.
Screw terminals
The screw terminals provide the following connections:
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Eight analog inputs (CH0 IN to CH7 IN)
Two analog outputs (D/A OUT 0 to D/A OUT 1)
16 digital I/O connections (PortA0 to Port A7, and Port B0 to Port B7)
One external trigger input (TRIG_IN)
One external event counter input (CTR)
One SYNC I/O for external clocking and multi-unit synchronization (SYNC)
One calibration output (CAL)
One power output (PC +5 V)
Five analog ground connections ( AGND) and four digital ground connections (GND)
One ground connection (GND)
Use 16 AWG to 30 AWG wire when making connections to the screw terminals. The single-ended mode pinout
is shown in Figure 3.
Figure 3. Single-ended mode pinout
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USB-1208FS User's Guide
Functional Details
The differential mode pinout is shown in Figure 4.
Figure 4. Differential mode pinout
Signal connections
Analog input
You can connect up to eight single-ended analog input connections to CH0 IN through CH7 IN, or four
differential connections to CH0 IN HI/LO through CH3 IN HI/LO.
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 12-bit resolution. When configured for single-ended
mode, each analog input has 11-bit resolution, due to restrictions imposed by the A/D converter.
Single-ended configuration
When 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:


Connect the wire carrying the signal to be measured to CH# IN.
Connect the second wire to AGND.
The input range for single-ended mode is ±10 V.
Single-ended measurements using differential channels
To perform a single-ended measurement using differential channels, connect the signal to the " CH# IN HI"
input, and ground the associated " CH# IN LO" input.
Differential configuration
When 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:



Connect the wire carrying the signal to be measured to CH# IN HI.
Connect the wire carrying the reference signal to CH# IN LO.
Connect the third wire to GND.
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USB-1208FS User's Guide
Functional Details
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 12-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 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 5).
Figure 5. 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 6).
Figure 6. 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 –3 V
to –11 V. Voltages between –10 V and –3 V are resolved, but those below –10 V are clipped (see Figure 7).
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USB-1208FS User's Guide
Functional Details
Figure 7. 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 table below shows some possible inputs and the expected results.
Sample inputs and differential results
CHHI
CHLO
Result
–20 V
–15 V
–10 V
–10 V
0V
0V
+10 V
+10 V
+15 V
+20 V
0V
+5 V
0V
+10 V
+10 V
+20 V
–10 V
0V
–5 V
0
Invalid
Invalid
–10 V
–20 V
–10 V
–20 V
+20 V
+10 V
+20 V
+20 V
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)
Channel-Gain queue
The channel gain queue feature allows you to set up a scan sequence with a unique per-channel gain setting and
channel sequence. 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 can contain up to 16 elements in any order. The channel-gain queue list can contain
up to 16 elements in any order. An example of a four-element list is shown in the table below..
Sample channel-gain queue list
Element
Channel
Range
0
1
2
3
CH0
CH0
CH7
CH2
BIP10V
BIP5V
BIP10V
BIP1V
When a scan begins with the gain queue enabled, the USB-1208FS 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.
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USB-1208FS User's Guide
Functional Details
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 acquired.
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.
Analog output
You can connect up to two analog output connections to D/A OUT 0 and D/A OUT 1. 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 5,000 updates per channel. The 0 V to 4.096 V output range provides a convenient 1 mV per
LSB when setting the output voltage levels.
Digital I/O
The device has 16 digital bits that are configured as two 8-bit ports (Port A and Port B). You can connect up to
eight digital I/O lines to each port (terminals Port A0 to Port A7 and Port B0 to Port B7). Each port is
configurable as either input or output.
When configured for input, you can use the digital I/O terminals to detect the state of any TTL level input.
Refer to the schematic shown in Figure 8.
Figure 8. Schematic showing switch detection by digital channel Port A0
If you set the switch to the +5V input, DIO0 reads TRUE (1). When set to GND, Port A0 reads FALSE (0).
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).
Pull-up/down configuration
Boards designed with hardware revision D and later have user-configurable internal jumpers 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 193331D.
If the p/n of your board is earlier than hardware revision D, the default configuration is pull-up. To configure
for pull-down, the board must be modified at the factory.
If your board has user-configurable jumpers, 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-1208FS 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.
The user-configurable jumpers are labeled DIO A and DIO B. Figure 9 shows the location of the each
jumper on the circuit board.
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USB-1208FS User's Guide
Functional Details
Figure 9. Pull-up/down jumper locations
5.
Configure each jumper for pull-up or pull-down, as shown in Figure 10. Use the jumper labeled DIO A to
configure Port A, and DIO B to configure Port B.
Figure 10. Pull-up/down jumper configuration
6.
Replace the top section of the housing, and fasten it to the bottom section with the three screws.
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 that you can configure for either rising or falling 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-1208FS device and acquire data from
16 channels. For more information synchronized operations see page 18.
Calibration output
The CAL terminal is an output used only to calibrate the device. Calibration is software-controlled via InstaCal.
Ground
The analog ground (AGND) terminals provide a common ground for all analog channels. The ground ( GND)
connections provide a common ground for the digital, trigger, counter, sync and power terminals.
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USB-1208FS User's Guide
Functional Details
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-1208FS and possibly the computer.
The maximum total output current that can be drawn from all USB-1208FS 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-1208FS to your computer draws 80 mA of current from the USB +5 V supply. Once
you start running applications with the USB-1208FS, 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-1208FS, 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 USB1208FS USB +5 V as follows:
(USB-1208FS @ 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 in the 350-380 mA range.
Since laptop computers typically allow up to 100 mA, the USB-1208FS 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.
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 "12-bits" or "1 part in
4,096" does indicate what can be resolved, it provides little insight into the quality of an absolute measurement.
Accuracy specifications describe the actual measurement achievable with a USB-1208FS.
There are three types of errors which affect the accuracy of a measurement system:



offset
gain
nonlinearity
The primary error sources in the USB-1208FS are offset and gain. Nonlinearity is small in the USB-1208FS,
and is not significant as an error source with respect to offset and gain.
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USB-1208FS User's Guide
Functional Details
Figure 11 shows an ideal, error-free, USB-1208FS transfer function. The typical calibrated accuracy of the
USB-1208FS is range-dependent, as explained in the Specifications chapter on page 20. We use a ±10 V range
here as an example of what you can expect when performing a measurement in this range.
Figure 11. Ideal ADC transfer function
The USB-1208FS offset error is measured at mid-scale. Ideally, a zero volt input should produce an output code
of 2048. Any deviation from this is an offset error. Figure 12 shows the USB-1208FS transfer function with an
offset error. The typical offset error specification on the ±10 V range is ±9.77 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 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-1208FS transfer function with gain error. Gain error is easily
converted to voltage by multiplying the full-scale (FS) input by the error.
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USB-1208FS User's Guide
Functional Details
The accuracy plots in Figure 13 are drawn for clarity and are not drawn to scale.
Figure 13. ADC Transfer function with gain error
For example, the USB-1208FS exhibits a typical calibrated gain error of ±0.2% on all ranges. For the ±10 V
range, this would yield 10 V × ±0.002 = ±20 mV. This means that at full scale, neglecting the effect of offset for
the moment, the measurement would be within 20 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-1208FS 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
Synchronized operations
You can run up to two USB-1208FS 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.
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USB-1208FS User's Guide
Functional Details
Mechanical drawings
Figure 15. 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
A/D converter type
Input voltage range for linear operation,
single-ended mode
Input common-mode voltage range for
linear operation, differential mode
Absolute maximum input voltage
Input impedance
Input current (Note 1)
Number of channels
Input ranges, single-ended mode
Input ranges, differential mode
Throughput (Note 2)
Channel gain queue
Resolution (Note 3)
CAL accuracy
Integral linearity error
Differential linearity error
Repeatability
CAL current
Trigger source
Pacer source
Conditions
Specification
CHx to GND
Successive approximation type
±10 volts (V) max
CHx to GND
–10 V min, +20 V max
CHx to GND
±28 V max
122 kΩ
70 µA typ
–12 µA typ
–94 µA typ
8 single-ended / 4 differential
±10 V, G=2
±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
250 S/s typ, PC-dependent
50 kS/s
Software configurable channel, range, and gain.
12 bits, no missing codes
11 bits
±36.25 mV max
±1 LSB typ
±0.5 LSB typ
±1 LSB typ
5 mA max
20 µA min, 100 µA typ
External digital: TRIG_IN
 Internal
 External (SYNC), rising edge triggered
 Programmed IO
Vin = +10 V
Vin = 0 V
Vin = –10 V
Software-selectable
Software-selectable
Software paced
Continuous scan
Up to 16 elements
Differential
Single-ended
CAL = 2.5 V
Source
Sink
Software-selectable
Software-selectable
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*V in – 12) µA.
Note 2: Maximum throughput scanning to PC memory is machine dependent.
Note 3: The AD7870 converter only returns 11-bits (0 to 2047 codes) in single-ended mode.
20
USB-1208FS User's Guide
Specifications
Table 2. Accuracy, differential mode
Range
Accuracy (LSB)
±20 V
±10 V
±5 V
±4 V
±2.5 V
±2 V
±1.25 V
±1 V
5.1
6.1
8.1
9.1
12.1
14.1
20.1
24.1
Table 3. Accuracy, single-ended mode
Range
Accuracy (LSB)
±10 V
4.0
Table 4. Accuracy components, differential mode - All values are (±)
Range
% of Reading
Gain Error at full scale (FS)
(millivolts (mV))
Offset (mV)
Accuracy at FS (mV)
±20 V
±10 V
±5 V
±4 V
±2.5 V
±2 V
±1.25 V
±1 V
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
40
20
10
8
5
4
2.5
2
9.766
9.766
9.766
9.766
9.766
9.766
9.766
9.766
49.766
29.766
19.766
17.766
14.766
13.766
12.266
11.766
Table 5. Accuracy components, single-ended mode - All values are (±)
Range
% of Reading
Gain Error at FS (mV)
Offset (mV)
Accuracy at FS (mV)
±10 V
0.2
20
19.531
39.531
Table 6. Noise performance, differential mode
Range
Typical counts
Least significant bitroot mean square (LSBrms)
±20 V
±10 V
±5 V
±4 V
±2.5 V
±2 V
±1.25 V
±1 V
2
2
3
3
4
5
7
8
0.30
0.30
0.45
0.45
0.61
0.76
1.06
1.21
Table 7. Noise performance, single-ended mode
Range
Typical Counts
LSBrms
±10 V
2
0.30
21
USB-1208FS User's Guide
Specifications
Analog output
Table 8. Analog output specifications
Parameter
Conditions
Resolution
Output range
Number of channels
Throughput (Note 4)
Specification
Software paced
Single channel, continuous scan
Dual channel, continuous scan,
simultaneous update
Power on and reset voltage
Output drive
Slew rate
12-bits, 1 in 4096
0 V to 4.096 V, 1 mV per LSB
2
250 S/s single channel typical, PC dependent
10 kS/s
5 kS/s
Initializes to 000h code
15 mA
0.8V/microsecond (µs) typ
Each D/A OUT
Note 4: Maximum throughput scanning to PC memory is machine dependent.
Table 9. Analog output accuracy, all values are (±)
Range
Accuracy (LSB)
0 V to 4.096 V
4.0 typ, 45.0 max
Table 10. Analog output accuracy components, all values are (±)
Range
% of FSR
Gain Error at FS (mV)
0 V to 4.096 V
0.1 typ, 0.9 max
4.0 typ, 36.0 max
Offset (mV)
(Note 5)
1.0 typ, 9.0 max
Accuracy at FS
(mV)
4.0 typ, 45.0 max
Note 5: Negative offsets will result in a fixed zero-scale error or "dead band." At the maximum offset of
–9 mV, any input code of less than 0x009 will not produce a response in the output.
Digital I/O
Table 11. Digital I/O specifications
Parameter
Specification
Digital type
Number of I/O
Configuration
Pull up/pull-down configuration
Input high voltage threshold
CMOS
16 (Port A0 through A7, Port B0 through B7)
2 banks of 8
All pins pulled up to 5V via 47 kΩ resistors (default).
Hardware revisions D and later may be changed to pull-down using an internal
user-configurable jumper.
Previous revisions can be configured at the factory for pull-down.
2.0 V min
Input high voltage limit
Input low voltage threshold
5.5 V absolute max
0.8 V max
Input low voltage limit
–0.5 V absolute min
0 V recommended min
3.84 V min
Output high voltage
(IOH = –6.0 mA)
Output low voltage
(IOL = 6.0 mA)
Power on and reset state
0.33 V max
Input
22
USB-1208FS User's Guide
Specifications
External trigger
Table 12. External digital trigger specifications
Parameter
Conditions
Specification
Trigger source
Trigger mode
External, digital
Software-selectable
TRIG_IN
Edge sensitive: user configurable for CMOS compatible rising or
falling edge
10 µs max
1 µs min
Schmitt trigger, 47 kΩ pull-down to ground
1.01 V typ
0.6 V min
1.5 V max
2.43 V typ
1.9 V min
3.1V max
5.5 V absolute max
1.42 V typ
1.0 V min
2.0 V max
-0.5 V absolute min
0 V recommended min
Trigger latency
Trigger pulse width
Input type
Schmitt trigger
hysteresis
Input high voltage
threshold
Input high voltage limit
Input low voltage
threshold
Input low voltage limit
External clock input/output
Table 13. External clock I/O specifications
Parameter
Pin name
Pin type
Direction
(software-selectable)
Input clock rate
Clock pulse width
Input type
Schmitt trigger
hysteresis
Input high voltage
threshold
Input high voltage limit
Input low voltage
threshold
Input low voltage limit
Output high voltage
Output low voltage
Conditions
Output
Input (default)
Input mode
Output mode
Specification
SYNC
Bidirectional
Outputs internal A/D pacer clock. Active on rising edge.
Receives A/D pacer clock from external source. Active on rising edge.
50 kHz, maximum
1 µs min
5 µs min
Schmitt trigger, 47 kΩ pull-down to ground
1.01 V typ
0.6 V min
1.5 V max
2.43 V typ
1.9 V min
3.1V max
5.5 V absolute max
1.42 V typ
1.0 V min
2.0 V max
-0.5 V absolute min
0 V recommended min
4.4 V min (IOH = –50 µA)
3.80 V min (IOH = –8 mA)
0.1 V max (IOL = 50 µA)
0.44 V max (IOL = 8 mA)
23
USB-1208FS User's Guide
Specifications
Counter
Table 14. Counter specifications
Parameter
Specification
Pin name
Counter type
Number of channels
Input type
Input source
Resolution
Maximum input frequency
High pulse width
Low pulse width
Schmitt trigger hysteresis
CTR
Event counter
1
Schmitt trigger, 47 kΩ pull-down to ground, rising edge triggered
CTR screw terminal
32 bits
1 MHz
500 ns min
500 ns min
1.01 V typ
0.6 V min
1.5 V max
2.43 V typ
1.9 V min
3.1V max
5.5 V absolute max
1.42 V typ
1.0 V min
2.0 V max
-0.5 V absolute min
0 V recommended min
Input high voltage threshold
Input high voltage limit
Input low voltage threshold
Input low voltage limit
Non-volatile memory
Table 15. Non-volatile memory specifications
EEPROM
EEPROM Configuration
1,024 bytes
Address Range
Access
Description
0x000 to 0x07F
0x080 to 0x1FF
0x200 to 0x3FF
Reserved
Read/write
Read/write
128 bytes system data
384 bytes cal data
512 bytes user area
Microcontroller
Table 16. Microcontroller specifications
Parameter
Specification
Type
High performance 16-bit RISC microcontroller
24
USB-1208FS User's Guide
Specifications
Power
Table 17. Power specifications
Parameter
Conditions
Supply current (Note 6)
+5V USB power available (Note 7)
Output current (Note 8)
Specification
Connected to self-powered hub
Connected to externally-powered root port hub
Connected to bus-powered hub
Connected to self-powered hub
Connected to externally-powered root port hub
Connected to bus-powered hub
80 mA
4.5 V min, 5.25 V max
4.1 V min, 5.25 V max
420 mA max
20 mA max
Note 6: This is the total current requirement for the USB-1208FS which includes up to 10 mA for the status
LED.
Note 7: Self-powered hub refers to a USB hub with an external power supply. Self-powered hubs allow a
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.
Note 8: This refers to the total amount of current that can be sourced from the USB +5 V, analog outputs and
digital outputs.
General
Table 18. General specifications
Parameter
Specification
Device type
Device compatibility
USB 2.0 full speed
USB 1.1, USB 2.0
Environmental
Table 19. Environmental specifications
Parameter
Specification
Operating temperature range
Storage temperature range
Humidity
0 °C to 70 °C
–40 °C to 70 °C
0% to 90% non-condensing
Mechanical
Table 20. Mechanical specifications
Parameter
Specification
Dimensions
USB cable length
User connection length
79 × 82 × 27 mm (3.10 × 3.20 × 1.05 in.)
3 m (9.84 ft) max
3 m (9.84 ft) max
25
USB-1208FS User's Guide
Specifications
Screw terminal connector
Table 21. Screw terminal specifications
Parameter
Specification
Connector type
Wire gauge range
Screw terminal
16 AWG to 30 AWG
Differential mode pinout
Table 22. 4-channel differential mode pinout
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Signal Name
CH0 IN HI
CH0 IN LO
AGND
CH1 IN HI
CH1 IN LO
AGND
CH2 IN HI
CH2 IN LO
AGND
CH3 IN HI
CH3 IN LO
AGND
D/A OUT 0
D/A OUT 1
AGND
CAL
GND
TRIG_IN
SYNC
CTR
Pin
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
Signal Name
Port A0
Port A1
Port A2
Port A3
Port A4
Port A5
Port A6
Port A7
GND
PC +5V
GND
Port B0
Port B1
Port B2
Port B3
Port B4
Port B5
Port B6
Port B7
GND
26
USB-1208FS User's Guide
Specifications
Single-ended mode pinout
Table 23. 8-channel single-ended mode pinout
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Signal Name
CH0 IN
CH1 IN
AGND
CH4 IN
CH3 IN
AGND
CH6 IN
CH5 IN
AGND
CH6 IN
CH7 IN
AGND
D/A OUT 0
D/A OUT 1
AGND
CAL
GND
TRIG_IN
SYNC
CTR
Pin
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
Signal Name
Port A0
Port A1
Port A2
Port A3
Port A4
Port A5
Port A6
Port A7
GND
PC +5V
GND
Port B0
Port B1
Port B2
Port B3
Port B4
Port B5
Port B6
Port B7
GND
27
Declaration of Conformity
Manufacturer:
Address:
Category:
Measurement Computing Corporation
10 Commerce Way
Suite 1008
Norton, MA 02766
USA
Electrical equipment for measurement, control and laboratory use.
Measurement Computing Corporation declares under sole responsibility that the product
USB-1208FS
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 1000-4-2 (1995): Electrostatic Discharge immunity, Criteria C.
IEC 1000-4-3 (1995): Radiated Electromagnetic Field immunity Criteria A.
IEC 1000-4-4 (1995): Electric Fast Transient Burst immunity Criteria C.
IEC 1000-4-5 (1995): Surge immunity Criteria A.
IEC 1000-4-6 (1996): Radio Frequency Common Mode immunity Criteria A.
IEC 1000-4-8 (1994): Magnetic Field immunity Criteria A.
IEC 1000-4-11 (1994): Voltage Dip and Interrupt immunity Criteria A.
Declaration of Conformity based on tests conducted by Chomerics Test Services, Woburn, MA 01801, USA in
August, 2004. Test records are outlined in Chomerics Test Report #EMI3948.04.
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
(508) 946-5100
Fax: (508) 946-9500
E-mail: [email protected]
www.mccdaq.com
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