Measurement Computing USB-1208FS-Plus User manual

USB-1208FS-Plus
Analog and Digital I/O
Document Revision 4A
November 2014
© Copyright 2014
User's Guide

HM USB-1208FS-Plus.docx
Trademark and Copyright Information
Measurement Computing Corporation, InstaCal, Universal Library, and the Measurement Computing logo are
either trademarks or registered trademarks of MeasurementComputing Corporation. Refer to the Copyrights &
Trademarks section on mccdaq.com/legal for more information about Measurement Computing trademarks.
Other product and company namesmentioned herein are trademarks or trade names of their respective
companies.
©2014 MeasurementComputingCorporation. All rights reserved. No part of this publicationmay be
reproduced, stored in a retrieval system, or transmitted, in any form by any means, electronic,mechanical, by
photocopying, recording, or otherwise without the prior written permission of Measurement Computing
Corporation.
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-1208FS-Plus.......................................................................................................6
Functional block diagram...................................................................................................................................6
Chapter 2
Installing the USB-1208FS-Plus...........................................................................................................7
What comes with your 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
External components ........................................................................................................................................10
USB connector.................................................................................................................................................................10
LED .................................................................................................................................................................................10
Screw terminals................................................................................................................................................................10
Signal connections............................................................................................................................................12
Analog input ....................................................................................................................................................................12
Analog output ..................................................................................................................................................................14
Digital I/O........................................................................................................................................................................15
Counter input...................................................................................................................................................................16
External trigger input.......................................................................................................................................................16
SYNC I/O ........................................................................................................................................................................16
Power output....................................................................................................................................................................16
Ground.............................................................................................................................................................................16
Accuracy...........................................................................................................................................................16
Synchronized operations...................................................................................................................................19
Power................................................................................................................................................................19
Mechanical drawings........................................................................................................................................20
Chapter 4
Specifications......................................................................................................................................21
Analog input.....................................................................................................................................................21
Accuracy..........................................................................................................................................................................22
Noise performance...........................................................................................................................................................22
Analog output...................................................................................................................................................23
Digital input/output...........................................................................................................................................23
External trigger.................................................................................................................................................24
External clock input/output...............................................................................................................................24

USB-1208FS-Plus User's Guide
4
Counter.............................................................................................................................................................25
Memory ............................................................................................................................................................25
Microcontroller.................................................................................................................................................25
Power................................................................................................................................................................25
General .............................................................................................................................................................26
Environmental ..................................................................................................................................................26
Mechanical .......................................................................................................................................................26
Signal connector ...............................................................................................................................................26
Differential mode pinout..................................................................................................................................................27
Single-ended mode pinout ...............................................................................................................................................27
Declaration of Conformity..................................................................................................................28

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-1208FS-Plus 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.
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-1208FS-Plus hardware is available on our website at www.mccdaq.com.
You can also contact Measurement Computing Corporation with specific questions.
Knowledgebase: kb.mccdaq.com
Tech support form: www.mccdaq.com/support/support_form.aspx
Email: [e-mail]
Phone: [phone] and follow the instructions for reaching Tech Support
For international customers, contact your local distributor. Refer to the International Distributors section on our
website at www.mccdaq.com/International.

6
Chapter 1
Introducing the USB-1208FS-Plus
The USB-1208FS-Plus is an analog input and digital I/O data acquisition device that provides the following
features:
Eight analog input channels that are software configurable for either eight 11-bit single-ended inputs or
four 12-bit differential inputs
Two 12-bit analog output channels
16 digital I/O channels that are independently-selectable as input or output in two 8-bit ports
32-bit event counter input for counting TTL pulses
External digital trigger input
Bidirectional terminal for external clocking or multi-unit synchronization
Screw terminals for field wiring connections
The device is powered by the +5 V USB supply from the computer. No external power is required.
Functional block diagram
Device functions are illustrated in the block diagram shown here.
Figure 1. USB-1208FS-Plus functional block diagram

7
Chapter 2
Installing the USB-1208FS-Plus
What comes with your shipment?
Verify that the following hardware components are included in the shipment.
Hardware
USB-1208FS-Plus
USB cable
Software
MCC DAQ CD
Documentation
MCC DAQ Quick Start
The MCC DAQ Quick Start 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.
DAQami Quick Start
The DAQami Quick Start insert provides information about the DAQami advanced data logging
application, including a quick start procedure and quick reference guide.
Unpacking
As with any electronic device, you should take care while handling to avoid damage from static
electricity. Before removing the device from its packaging, ground yourself using a wrist strap or by simply
touching the computer chassis or other grounded object to eliminate any stored static charge.
Contact us immediately if any components are missing or damaged.
Installing the software
Refer to the MCC DAQ Quick Start for instructions on installing the software on the MCC DAQ CD. Refer to
the device product page on the Measurement Computing website for information about the included and
optional software supported by the USB-1208FS-Plus.
Install the software before you install your device
The driver needed to run the USB-1208FS-Plus is installed with 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.
Installing the hardware
To connect the device to your system, turn on your computer and connect the USB cable to an available USB
port on the computer or to an externally powered 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 connected for the first time, a Found New Hardware dialog opens when the operating system detects the
device. When the dialog box closes, the installation is complete. The LED turns on after the device is
successfully installed.

USB-1208FS-Plus User's Guide Installing the USB-1208FS-Plus
8
Caution! Do not disconnect any device from the USB bus while the computer is communicating with the
device, or you may lose data and/or your ability to communicate with the device.
If the LED turns off
If the LED is on but then turns off, the computer has lost communication with the 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.
Calibrating the hardware
The Measurement Computing Manufacturing Test department performs the initial factory calibration. Return
the device to Measurement Computing Corporation when calibration is required. The recommended calibration
interval is one year.
The USB-1208FS-Plus does not support field calibration.

9
Chapter 3
Functional Details
Analog input acquisition modes
The USB-1208FS-Plus can acquire analog input data in either software paced or hardware paced mode.
Software paced
The USB-1208FS-Plus 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 maximum sample rate in software-paced mode is system-dependent.
Hardware paced
The USB-1208FS-Plus can acquire data from up to eight channels using hardware-paced mode. The analog data
is acquired and converted to digital values until you stop the scan. Data is transferred in blocks of 32 samples
from the device 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 cannot exceed 50 kS/s.
The following table lists the sample rate when scanning from one to eight channels.
Maximum per channel sample rate
# channels
scanned
Sample rate
(kS/s)
1
50
2
25
3
16.70
4
12.50
5
10
6
8.30
7
7.14
8
6.25
You can start a hardware-paced scan with a software command. Optionally, hardware-paced scans can be
delayed by an external hardware trigger event.

USB-1208FS-Plus User's Guide Functional Details
10
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. External components
USB connector
Receives the supplied USB cable. When connected to a computer or USB hub, the cable provides power and
communication. No external power supply is required.
LED
The following table lists the behavior of the device LED.
LED state
Indication
Steady green
The device is connected to a computer or external USB hub.
Blinks continuously
Data is being transferred.
Screw terminals
The screw terminals provide the following connections:
Eight analog input connections (CH0 IN to CH7 IN, CH0 IN HI/LO through CH3 IN HI/LO)
Two analog output connections (D/A OUT 0 to D/A OUT 1)
16 digital I/O connections (PortA0 to Port A7, and Port B0 to Port B7)
External trigger input (TRIG_IN)
External counter input (CTR)
Bidirectional terminal for external clocking or multi-unit synchronization (SYNC)
Power output (+VO)
Analog ground (AGND) and ground (GND)
Use 16 AWG to 30 AWG wire when making connections to the screw terminals.

USB-1208FS-Plus User's Guide Functional Details
11
The single-ended mode pinout is shown in Figure 3.
Figure 3. Single-ended mode pinout
The differential mode pinout is shown in Figure 4.
Figure 4. Differential mode pinout

USB-1208FS-Plus User's Guide Functional Details
12
Signal connections
Analog input
You can connect up to eight analog input connections to the screw terminal bank containing pins 1 to 20.
You can configure the analog input channels as eight single-ended channels (CH0 IN through CH7 IN)or four
differential channels (CH0 IN HI/LO through CH3IN HI/LO). 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, 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. The single-ended mode pinout is shown in Figure 3 on page
11.
Differential configuration
When configured for differential input mode, the input signal is measured with respect to the low input and
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.
The differential mode pinout is shown in Figure 4 on page 11.
Note: To perform a single-ended measurement using differential channels, connect the signal to CH# IN HI and
ground the associated CH# IN LO input.
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 given analog input pair must remain within the selected voltage
range.
The input [common-mode voltage + signal] of the differential channel must be in the −10 V to +20 V range in
order to yield a useful result.

USB-1208FS-Plus User's Guide Functional Details
13
For example, you input a 4 V pp sine wave to CH# IN HI, and apply the same sine wave 180° out of phase to
CH# IN LO. 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 [common-mode
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, as shown in
Figure 7.
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 CH# IN HI and 0 V on CH# IN LO, since
this violates the input range criteria.

USB-1208FS-Plus User's Guide Functional Details
14
The table below shows some possible inputs and the expected results.
Sample inputs and differential results
CH# IN HI
CH# IN LO
Result
–20 V
0 V
Invalid
–15 V
+5 V
Invalid
–10 V
0 V
–10 V
–10 V
+10 V
–20 V
0 V
+10 V
–10 V
0 V
+20 V
–20 V
+10 V
–10 V
+20 V
+10 V
0 V
+10 V
+15 V
–5 V
+20 V
+20 V
0
+20 V
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 settings are stored in a channel-gain queue list that is written to local memory on the
device. The gain queue can contain up to eight elements in single-ended mode, and up to four elements in
differential mode.
The elements must be unique and listed in ascending order. An example of a three-element list is shown in the
table below.
Sample channel-gain queue list
Element
Channel
Range
Gain
0
CH0
BIP10V
2
1
CH1
BIP20V
1
2
CH3
BIP4V
5
When a scan begins with the gain queue enabled, the device reads the first element, sets the appropriate channel
number, range, and gain, and then acquires a sample. The properties of the next element are then retrieved, and
another sample is acquired. This sequence continues until all elements in the gain queue have been selected.
When the end of the channel list is detected, the sequence returns to the first element in the list. The 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.
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
You can connect up to two analog output connections to D/A OUT 0 and D/A OUT 1. Each channel can be paced
at rates up to 50,000 updates per second. The output range is 0 V to 5 V.

USB-1208FS-Plus User's Guide Functional Details
15
Digital I/O
The device has 16 DIO channels that are configured as two 8-bit ports –Port A and Port B. Port B is high drive.
You can connect up to eight DIO lines to Port A0 to Port A7 and up to eight DIO lines to Port B0 to Port B7.
You can configure each port for either input or output. The digital ports are set for input when the device is
powered on or reset.
When configured for input, the digital I/O terminals can detect the state of any TTL-level. 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, Port A0 reads TRUE (1). When set to GND, Port A0 reads FALSE (0).
Pull-up/down configuration
All digital I/O lines are pulled high to USB +5 V with a 47 kΩ resistor by default. You can change the
pull-up/down configuration using the internal jumper labeled DIO. You must remove the device housing to
access the jumper on the circuit board.
Complete the following steps to set the jumper for pull-up or pull-down:
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-Plus 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 each jumper on
the circuit board.
Figure 9. Pull-up/down jumper locations
5. Set each jumper for pull-up (P/UP) or pull-down (P/DN), as shown in Figure 10. Use the jumper labeled
DIO A to configure Port A, and DIO B to configure Port B.

USB-1208FS-Plus User's Guide Functional Details
16
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.
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).
Counter input
The CTR connection is input to the 32-bit external event. The internal counter increments when the TTL levels
transition from low to high. The counter can count frequencies of up to 1 MHz.
External trigger input
The TRIG_IN connection is an external 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 pace the A/D conversions from an external source. The SYNC
terminal supports TTL-level input signals of up to 50 kHz.
Configure as an output to pace the conversions on a second device and acquire data from 16 channels using
one clock. For more information about synchronized operations see page 19.
Power output
The +VO connection draws power from the USB connector on the computer.
Caution! The +VO terminal is an output. Do not connect it 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, trigger, counter, and sync
channels and the power terminal.
Accuracy
The overall accuracy of any instrument is limited by the error components within the system. Resolution is
often incorrectly used 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 results that can be realized with a measurement device.
There are three types of errors which affect the accuracy of a measurement system:
offset
gain
nonlinearity
The primary error sources are offset and gain. Nonlinearity is small in each device, and is not significant as an
error source with respect to offset and gain.

USB-1208FS-Plus User's Guide Functional Details
17
Figure 11 shows an ideal, error-free transfer function. The typical calibrated accuracy is range-dependent. Refer
to the "Accuracy specifications" on page 22 for more information. 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 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 an example of a transfer function with a ±9.77 mV offset error. Offset error affects all codes
equally by shifting the entire transfer function up or down along the input voltage axis.
The accuracy plots in Figure 12 are drawn for clarity and are not drawn to scale.
Figure 12. ADC transfer function with offset error

USB-1208FS-Plus User's Guide Functional Details
18
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 transfer function with gain error. Gain error is easily converted to voltage by multiplying
the full-scale (FS) input by the error.
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-Plus 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, and neglecting the effect
of offset, 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 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

USB-1208FS-Plus User's Guide Functional Details
19
Synchronized operations
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. Output the clock signal to the SYNC pin of a second device that is configured for A/D pacer input.
Power
Connecting the device to a computer draws <100 mA of current from the USB +5V supply. When running
applications, the current that can be drawn from all device connections (analog, digital, SYNC, and +VO output
loading) is <500 mA. The maximum output current that is available at the +VO power output terminal is
100 mA.
With all outputs at their maximum output current, the USB-1208FS-Plus in a fully-loaded configuration may be
above that allowed by the computer. In this case, determine the per-pin loading in the application to ensure that
the maximum loading criteria is met. The per-pin loading is calculated by dividing +5V by the load impedance
of the pin in question.

USB-1208FS-Plus User's Guide Functional Details
20
Mechanical drawings
Figure 15. Circuit board (top) and enclosure dimensions