Measurement Computing USB-1208FS User Manual
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Measurement Computing USB-1208FS User Manual

Low-cost, usb-based module with 8 channels, 12-bit input
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Summary of Contents for Measurement Computing USB-1208FS

  • Page 2 USB-1208FS Analog and Digital I/O User's Guide Document Revision 6, March, 2010 © Copyright 2010, Measurement Computing Corporation...
  • Page 3 Management committed to your satisfaction! Thank you for choosing a Measurement Computing product—and congratulations! You own the finest, and you can now enjoy the protection of the most comprehensive warranties and unmatched phone tech support. It’s the embodiment of our mission: ...
  • Page 4 Information furnished by Measurement Computing Corporation is believed to be accurate and reliable. However, no responsibility is assumed by Measurement Computing Corporation neither for its use; nor for any infringements of patents or other rights of third parties, which may result from its use. No license is granted by implication or otherwise under any patent or copyrights of Measurement Computing Corporation.

  • Page 5: Table Of Contents

    Chapter 1 Introducing the USB-1208FS........................ 8 USB-1208FS block diagram ..........................9 Software features ..............................9 Connecting a USB-1208FS to your computer is easy..................10 Chapter 2 Installing the USB-1208FS ........................11 What comes with your USB-1208FS shipment? ....................11 Hardware ..................................11 Additional documentation ..............................11...
  • Page 6 USB-1208FS User's Guide Microcontroller ..............................29 Power ................................29 General ................................30 Environmental ..............................30 Mechanical ............................... 30 Main connector and pin out ..........................30 4-channel differential mode .............................31 8-channel single-ended mode ............................31 Declaration of Conformity ........................32...

  • Page 7: Preface

    About this User's Guide What you will learn from this user's guide This user's guide explains how to install, configure, and use the USB-1208FS so that you get the most out of its USB data acquisition features. This user's guide also refers you to related documents available on our web site, and to technical support resources.

  • Page 8: Introducing The Usb-1208Fs

    Chapter 1 Introducing the USB-1208FS This user's guide contains all of the information you need to connect the USB-1208FS to your computer and to the signals you want to measure. ® ® The USB-1208FS is a USB 2.0 full-speed device supported under popular Microsoft...

  • Page 9: Usb-1208Fs Block Diagram

    USB-1208FS functions are illustrated in the block diagram shown here. Figure 2. USB-1208FS functional block diagram Software features For information on the features of InstaCal and the other software included with your USB-1208FS, refer to the Quick Start Guide that shipped with your device.

  • Page 10: Connecting A Usb-1208Fs To Your Computer Is Easy

    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. ...

  • Page 11: Installing The Usb-1208Fs

    As with any electronic device, you should 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 by simply touching the computer chassis or other grounded object to eliminate any stored static charge.

  • Page 12: Installing The Software

    USB drivers. To connect the USB-1208FS to your system, turn your computer on, and connect the USB cable to a USB port on your computer or to an external USB hub that is connected to your computer. The USB cable provides power and communication to the USB-1208FS.

  • Page 13: Chapter 3 Functional Details

    Functional Details Theory of operation - analog input acquisition modes The USB-1208FS can acquire analog input data in two different modes – software paced and continuous scan. Maximum throughput is system-dependent Maximum throughput may be lower in Windows operating systems that predate Windows XP.

  • Page 14: Usb Connector

    5 V. No external power supply is required. The LED on the front of the housing indicates the communication status of the USB-1208FS. It uses up to 5 mA of current and cannot be disabled. The table below defines the function of the USB-1208FS LED.

  • Page 15: Main Connector And Pin Out

    USB-1208FS User's Guide Functional Details Screw terminal – pins 21-40 The screw terminals on the bottom edge of the (pins 21 to 40) provide the following connections:  16 digital I/O connections ( , and PortA0 Port A7 Port B0 Port B7 ...
  • Page 16 USB-1208FS User's Guide Functional Details Figure 5. Single-ended measurement connection Battery voltage should read as expected when the hardware is configured for single-ended mode. Single-ended measurements using differential channels To perform a single-ended measurement using differential channels, connect the signal to "CHn IN HI" input, and ground the associated "CHn IN LO"...
  • Page 17 USB-1208FS User's Guide Functional Details Figure 6. Differential voltage example: common mode voltage of 0 V If you increase the common mode voltage to 11 V, the differential remains at ±8 V. Although the [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 7).

  • Page 18: Analog Output Terminals (D/A Out 0 And D/A Out 1)

    USB-1208FS User's Guide Functional Details The table below shows some possible inputs and the expected results. Sample inputs and differential results CHHI CHLO Result -20 V In Valid -15 V +5 V In Valid -10 V -10 V -10 V...

  • Page 19: Power Terminals

    1208FS 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.

  • Page 20: Ground Terminals

     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. 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"...
  • Page 21 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.
  • Page 22 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.

  • Page 23: Usb-1208Fs Channel Gain Queue Feature

    In the Gated mode, it is assumed that the clock signal will be held off for an adequate amount of time for setup to occur. No clock pulses are ignored. Use this mode if the USB-1208FS is set up as a slave and the source of the external clock is another USB.
  • Page 24 This InstaCal option does not affect internally paced acquisition. It only affects scans that use the option. An example of a master/slave configuration is shown below. Figure 15. Configuring for synchronous data acquisition EXTCLOCK When you are operating one USB-1208FS, do not set the option unless you are using an external clock for A/D pacing.

  • Page 25: Specifications

    Chapter 4 Specifications Typical for 25°C unless otherwise specified. Specifications in italic text are guaranteed by design. Analog input Table 1. Analog input specifications Parameter Conditions Specification A/D converter type Successive approximation type Input voltage range for linear operation, CHx to GND ±10 volts (V) max single-ended mode Input common-mode voltage range for linear...
  • Page 26 USB-1208FS User's Guide Specifications Note 2: Maximum throughput scanning to PC memory is machine dependent. The rates specified are for Windows XP only. Maximum rates on operating systems that predate XP may be less and must be determined through testing on your machine Note 3: The AD7870 converter only returns 11-bits (0-2047 codes) in single-ended mode.

  • Page 27: Analog Output

    USB-1208FS User's Guide Specifications Table 7. Noise performance, single-ended mode Range Typical Counts ±10 V 0.30 Analog output Table 8. Analog output specifications Parameter Conditions Specification Resolution 12-bits, 1 in 4096 0 – 4.096 V, 1 mV per LSB. Output range...

  • Page 28: External Trigger

    USB-1208FS User's Guide Specifications External trigger Table 12. Digital trigger specifications Parameter Conditions Specification Trigger source (Note 6) External Digital TRIG_IN Trigger mode Software selectable Edge sensitive: user configurable for CMOS compatible rising or falling edge. Trigger latency 10 µs max Trigger pulse width 1 µs min...

  • Page 29: Counter

    Connected to self-powered hub 420 mA max Connected to externally-powered root port hub Connected to bus-powered hub 20 mA max This is the total current requirement for the USB-1208FS which includes up to 10 mA for the Note 9: status LED.

  • Page 30: General

    USB-1208FS User's Guide Specifications Note 10: 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.

  • Page 31: 4-Channel Differential Mode

    USB-1208FS User's Guide Specifications 4-channel differential mode Signal Name Signal Name CH0 IN HI Port A0 CH0 IN LO Port A1 AGND Port A2 CH1 IN HI Port A3 CH1 IN LO Port A4 AGND Port A5 CH2 IN HI...

  • Page 32: Declaration Of Conformity

    Norton, MA 02766 Category: 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...
  • Page 33 Measurement Computing Corporation 10 Commerce Way Suite 1008 Norton, Massachusetts 02766 (508) 946-5100 Fax: (508) 946-9500 E-mail: info@mccdaq.com www.mccdaq.com...

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