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OM-USB-1208FS
User Manual
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Omega OM-USB-1208FS User Manual

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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 OM-USB-1208FS ........................................................................................................ 6
OM-USB-1208FS block diagram ....................................................................................................................... 7
Software features ................................................................................................................................................ 7
Connecting a OM-USB-1208FS to your computer is easy ................................................................................. 8
Chapter 2
Installing the OM-USB-1208FS ............................................................................................................ 9
What comes with your OM-USB-1208FS shipment?......................................................................................... 9
Hardware .......................................................................................................................................................................... 9
Additional documentation ................................................................................................ ................................................. 9
Unpacking the OM-USB-1208FS ....................................................................................................................... 9
Installing the software ...................................................................................................................................... 10
Installing the hardware ..................................................................................................................................... 10
Chapter 3
Functional Details ............................................................................................................................... 11
Theory of operation - analog input acquisition modes ..................................................................................... 11
Software paced mode .......................................................................................................................................................11
Continuous scan mode .....................................................................................................................................................11
External components ........................................................................................................................................ 11
USB connector .................................................................................................................................................................12
LED .................................................................................................................................................................................12
Screw terminal wiring ......................................................................................................................................................12
Main connector and pin out .............................................................................................................................................13
Analog input terminals (CH0 IN - CH7 IN).....................................................................................................................13
Analog output terminals (D/A OUT 0 and D/A OUT 1) ..................................................................................................16
Digital I/O terminals (Port A0 to A7, and Port B0 to B7) ................................................................................................16
Power terminals ...............................................................................................................................................................16
Calibration terminal .........................................................................................................................................................17
Ground terminals .............................................................................................................................................................17
External trigger terminal ..................................................................................................................................................17
SYNC terminal ................................................................................................................................................................17
Counter terminal ..............................................................................................................................................................17
Accuracy ........................................................................................................................................................... 18
OM-USB-1208FS channel gain queue feature ................................................................................................. 20
Synchronizing multiple units ............................................................................................................................ 21
Chapter 4
Specifications ...................................................................................................................................... 22
Analog input ..................................................................................................................................................... 22
Analog output ................................................................................................................................................... 24
Digital input/output........................................................................................................................................... 24
External trigger ................................................................................................................................................. 25
External clock input/output............................................................................................................................... 25
Counter ............................................................................................................................................................. 25
Non-volatile memory ........................................................................................................................................ 26
3
Microcontroller ................................................................................................................................................. 26
Power ................................................................................................................................ ................................ 26
General ............................................................................................................................................................. 27
Environmental .................................................................................................................................................. 27
Mechanical ....................................................................................................................................................... 27
Main connector and pin out .............................................................................................................................. 27
4-channel differential mode .............................................................................................................................................27
8-channel single-ended mode ...........................................................................................................................................28
4

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 OM-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.

Conventions in this user’s guide

For more information on …
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.
< : > Angle brackets that enclose numbers separated by a colon signify a range of numbers, such as those assigned
to registers, bit settings, etc.
bold text Bold text is used for the names of objects on the screen, such as buttons, text boxes, and check boxes. For
example:
1. Insert the disk or CD and click the OK button.
italic text Italic text is used for the names of manuals and help topic titles, and to emphasize a word or phrase. For
example: Never touch the exposed pins or circuit connections on the board.

Where to find more information

For additional information relevant to the operation of your hardware, refer to the Documents subdirectory where you installed the software, or search for your device on our website at www.omega.com.
5
Chapter 1

Introducing the OM-USB-1208FS

This user's guide contains all of the information you need to connect the OM-USB-1208FS to your computer and to the signals you want to measure.
The OM-USB-1208FS is a USB 2.0 full-speed 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 OM-USB-1208FS features eight analog inputs, two 12-bit analog outputs, 16 digital I/O connections, and one 32-bit external event counter. The OM-USB-1208FS is powered by the +5 volt USB supply from your computer. No external power is required.
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 OM-USB-1208FS is shown in Figure 1. I/O connections are made to the screw terminals located along each side of the OM-USB-1208FS.
Figure 1. OM-USB-1208FS
6

OM-USB-1208FS block diagram

OM-USB-1208FS functions are illustrated in the block diagram shown here.
Figure 2. OM-USB-1208FS functional block diagram

Software features

For information on the features of InstaCal and the other software included with your OM-USB-1208FS, refer to the OMB-DAQ-2416 Series and OM-USB Series Data Acquisition Software User’s Guide that shipped with your device.
7

Connecting a OM-USB-1208FS to your computer is easy

Installing a data acquisition device has never been easier. The OM-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 OM-USB-1208FS. No third-party device driver is required.
The OM-USB-1208FS is plug-and-play. There are no jumpers to position, DIP switches to set, or interrupts
to configure.
You can connect the OM-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 OM-USB-1208FS units 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 can flow two ways between a computer and peripheral over USB connections.
8

Installing the OM-USB-1208FS

What comes with your OM-USB-1208FS shipment?

As you unpack your OM-USB-1208FS, verify that the following components are included.

Hardware

OM-USB-1208FS (shown with cable)
Chapter 2
USB cable (2 meter length)

Additional documentation

In addition to this hardware user's guide, you should also receive the OMB-DAQ-2416 Series and OM-USB Series Data Acquisition Software User’s Guide. This booklet supplies a brief description of the software you
received with your OM-USB-1208FS and information regarding installation of that software. Please read this booklet completely before installing any software or hardware.

Unpacking the OM-USB-1208FS

As with any electronic device, you should take care while handling to avoid damage from static electricity. Before removing the OM-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.
If any components are missing or damaged, notify Omega Engineering immediately by phone, fax, or e-mail.
Phone: (203) 359-1660 Fax: (203) 359-7700 Email: das@omega.com
9

Installing the software

Refer to the OMB-DAQ-2416 Series and OM-USB Series Data Acquisition Software User’s Guide for instructions on installing the software on the OMB-DAQ-2416 Series and OM-USB Series Data Acquisition Software CD. This booklet is available in PDF at http://www.omega.com/manuals/manualpdf/M4803.pdf.
We recommend that you download the latest Windows Update onto your computer before installing and operating the OM-USB-1208FS.

Installing the hardware

Be sure you are using the latest system software
Before you install your OM-USB-1208FS, run Windows Update to update your operating system with the latest HID and USB drivers.
To connect the OM-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 OM-USB-1208FS.
When you connect the OM-USB-1208FS for the first time, a series of Found New Hardware popup balloons (Windows XP) or dialogs (other Windows versions) opens as the OM-USB-1208FS is detected by your computer. This is normal. The last popup balloon or dialog states "Your new hardware is installed and ready to use," and the LED on the OM-USB-1208FS should flash and then remain lit. This indicates that communication is established between the OM-USB-1208FS and your computer.
You can install up to two OM-USB-1208FS units on most computers. If you need to connect more than two OM-USB-1208FS units to your computer, contact Tech Support by phone, fax, or e-mail:
Phone: (203) 359-1660 Fax: (203) 359-7700 Email: das@omega.com
Caution! Do not disconnect any device from the USB bus while the computer is communicating with the
OM-USB-1208FS, or you may lose data and/or your ability to communicate with the OM-USB­1208FS.
If the LED turns off
If the LED is illuminated but then turns off, the computer has lost communication with the OM-USB-1208FS. To restore communication, disconnect the USB cable from the computer, and then reconnect it. This should restore communication, and the LED should turn back on.
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Chapter 3

Functional Details

Theory of operation - analog input acquisition modes

The OM-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.

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 can 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.

Continuous scan mode

In continuous scan 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 OM-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 OM-USB-1208FS has the following external components, as shown in Figure 3.
USB connector LED Screw terminal banks (2)
Figure 3. OM-USB-1208FS external components
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LED Illumination
Indication
Steady green
The OM-USB-1208FS is connected to a computer or external USB hub.
Blinks continuously
Data is being transferred.

USB connector

The USB connector is on the right side of the OM-USB-1208FS. This connector provides +5 V power and communication. The voltage supplied through the USB connector is system-dependent, and may be less than 5 V. No external power supply is required.
LED
The LED on the front of the housing indicates the communication status of the OM-USB-1208FS. It uses up to 5 mA of current and cannot be disabled. The table below defines the function of the OM-USB-1208FS LED.
LED Illumination

Screw terminal wiring

The OM-USB-1208FS has two rows of screw terminals—one row on the top edge of the housing, and one row on the bottom edge. Each row has 20 connections. Pin numbers are identified in Figure 4.
Figure 4. OM-USB-1208FS Screw terminal pin numbers
Screw terminal – pins 1-20
The screw terminals on the top edge of the OM-USB-1208FS (pins 1 to 20) provide the following connections:
Eight analog input connections (CH0 IN to CH7 IN) Two analog output connections (D/A OUT 0 to D/A OUT 1) One external trigger source (TRIG_IN) One SYNC terminal for external clocking and multi-unit synchronization (SYNC) One calibration terminal (CAL) Five analog ground connections (AGND) One ground connection (GND) One external event counter connection (CTR)
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Connector type
Screw terminal
Wire gauge range
16 AWG to 30 AWG
8-channel single-ended mode pin out
4-channel differential mode pin out
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 (PortA0 to Port A7, and Port B0 to Port B7) One power connection (PC+5 V) Three ground connections (GND)

Main connector and pin out

Analog input terminals (CH0 IN - CH7 IN)

You can connect up to eight analog input connections to the screw terminal containing pins 1 to 20 (CH0 IN through CH7 IN.) Refer to the pinout diagrams above for the location of these pins.
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 all of the analog input channels are 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:
The wire carrying the signal to be measured connects to CHn IN. The second wire connects to AGND.
The input range for single-ended mode is ±10 V. No other ranges are supported in single-ended mode.
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Single-ended measurements using differential channels
To perform a single-ended measurement using differential channels, connect the signal to CHn IN HI, and ground the associated CHn IN LO input.
Differential configuration
When all of 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: The wire carrying the signal to be measured connects to CH0 IN HI, CH1 IN HI, CH2 IN HI, or
CH3 IN HI.
The wire carrying the reference signal connects to CH0 IN LO, CH1 IN LO, CH2 IN LO, or
CH3 IN LO.
The third wire connects to GND. 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. 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).
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CHHI
CHLO
Result
-20 V
0 V
In Valid
-15 V
+5 V
In Valid
-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
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).
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
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For more information on analog signal connections
For more information on single-ended and differential inputs, refer to the the OMB-DAQ-2416 Series and OM­USB Series General Guide to Signal Connections (available on our web site at
www.omega.com/manuals/manualpdf/M4830.pdf).

Analog output terminals (D/A OUT 0 and D/A OUT 1)

You can connect up to two analog output connections to the screw terminal pins 13 and 14 (D/A OUT 0 and D/A
OUT 1). Refer to the pinout diagrams on page 13 for the location of these pins.
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 5000 updates per channel. The 0-4.096 V output range provides a convenient 1 mV per LSB when setting the output voltage levels.

Digital I/O terminals (Port A0 to A7, and Port B0 to B7)

You can connect up to 16 digital I/O lines to the screw terminal containing pins 21 to 40 (Port A0 to Port A7, and Port B0 to Port B7.) Refer to the pinout diagrams on page 13 for the location of these pins. You can configure each digital port for either input or output.
When you configure the digital bits 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. If the switch is set to the +5 V input, Port A0 reads TRUE (1). If you move the switch to GND, Port A0 reads FALSE.
Figure 8. Schematic showing switch detection by digital channel Port A0
For more information on digital signal connections
For more information on digital signal connections and digital I/O techniques, refer to the OMB-DAQ-2416 Series and OM-USB Series General Guide to Signal Connections (available on our web site at
www.omega.com/manuals/manualpdf/M4830.pdf).

Power terminals

The PC +5V connection (pin 30) is on the bottom screw terminal of the OM-USB-1208FS. Refer to the pinout diagrams on page 13 for the location of this pin. This terminal draws power from the USB connector. The +5 V screw terminal is a 5 volt output that is supplied by the host computer.
Caution! The +5 V terminal is an output. Do not connect to an external power supply or you may damage
the OM-USB-1208FS and possibly the computer.
The maximum total output current that can be drawn from all OM-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 OM-USB-1208FS to your computer draws 80 mA of current from the USB +5 V supply. Once you start running applications with the OM-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 OM-USB-1208FS, is the difference between the total current requirement of the
16
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 OM­USB-1208FS USB +5 V as follows:
(OM-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 OM-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.

Calibration terminal

The CAL connection (pin 16) is an output you should use only to calibrate the OM-USB-1208FS. Refer to the pinout diagrams on page 13 for the location of this pin. Calibration of the OM-USB-1208FS is software­controlled via InstaCal.

Ground terminals

The four analog ground (AGND) connections provide a common ground for all OM-USB-1208FS input channels. Four ground (GND) connections provide a common ground for the DIO, TRIG_IN, CTR, SYNC and
PC +5V connections. Refer to the pinout diagrams on page 13 for the location of the AGND and GND pins.

External trigger terminal

The TRIG_IN connection (pin 18) can be configured for either rising or falling edge. Refer to the pinout diagrams on page 13 for the location of the TRIG_IN terminal pin.

SYNC terminal

The SYNC connection (pin 19) is a bidirectional I/O signal. You can use it for two purposes: 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 synchronize with a second USB unit and acquire data from 16 channels. Refer to the pinout diagrams on page 13 for the location of this pin. For more information on synchronizing
multiple units, refer to page 21.

Counter terminal

The CTR connection (pin 20) is input to the 32-bit external event. Refer to the pinout diagrams on page 13 for the location of this pin. The internal counter increments when the TTL levels transition from low to high. The counter can count frequencies of up to 1 MHz.
17

Accuracy

The overall accuracy of any instrument is limited by the error components within the system. Quite often, resolution is incorrectly used to quantify the performance of a measurement product. While "12-bits" or "1 part in 4096" 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 in the OM-USB-1208FS are offset and gain. Nonlinearity is small in the OM-USB­1208FS, and is not significant as an error source with respect to offset and gain.
Figure 9 shows an ideal, error-free, OM-USB-1208FS transfer function. The typical calibrated accuracy of the OM-USB-1208FS is range-dependent, as explained in the "Specifications" chapter on page 22. We use a ±10 V range here as an example of what you can expect when performing a measurement in this range.
Figure 9. Ideal ADC transfer function
The OM-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 10 shows the OM-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 10 are drawn for clarity and are not drawn to scale.
18
Figure 10. 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 11 shows the OM-USB-1208FS 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 11 are drawn for clarity and are not drawn to scale.
Figure 11. ADC Transfer function with gain error
For example, the OM-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 mid­scale, which see little or no voltage error.
Combining these two error sources in Figure 12, we have a plot of the error band of the OM-USB-1208FS for the ±10 V range. This is a graphical version of the typical accuracy specification of the product.
19
Element
Channel
Range
0
CH0
BIP10V
1
CH0
BIP5V
2
CH7
BIP10V
3
CH2
BIP1V
The accuracy plots in Figure 12 are drawn for clarity and are not drawn to scale.
Figure 12. Error band plot

OM-USB-1208FS channel gain queue feature

The OM-USB-1208FS's channel gain queue feature allows you to set up a scan sequence with a unique per­channel gain setting and channel sequence.
The channel gain queue feature removes the restriction of using an ascending channel sequence at a fixed gain. This feature creates a channel list which is written to local memory on the OM-USB-1208FS. The channel list is made up of a channel number and range setting. An example of a four-element list is shown in the table below.
Sample channel gain queue list
When a scan begins with the gain queue enabled, the OM-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. 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 gathered. You must carefully match the gain to the expected voltage range on the associated channel — otherwise, an over range condition can occur. Although this condition does not damage the OM-USB-1208FS, it does produce a useless full-scale reading. It can also introduce a long recovery time from saturation, which can affect the next measurement in the queue.
20

Synchronizing multiple units

You can run up to two OM-USB-1208FS units on most computers.
You can connect the SYNC pin of two OM-USB-1208FS units 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 is sent to the screw terminal. You can use this signal as a clock input to a second USB by connecting it to the SYNC pin of the second USB.
When used as a clock input, the SYNC pin operates in one of two modes – Continuous or Gated.
In the default Continuous mode, a OM-USB-1208FS ignores the first clock pulse in order to ensure adequate setup time. Use this mode if the unit is being paced from a continuous clock source, such as a generator.
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 OM-USB-1208FS is set up as a slave and the source of the external clock is another USB.
The SYNC pin (pin 19) is set for pacer output by default. To set it to input requires a software command (see Figure 13 below).
To synchronize a master OM-USB-1208FS with a slave OM-USB-1208FS and acquire data, follow the steps below.
1. Connect the SYNC pin of the master OM-USB-1208FS to the SYNC pin of the slave OM-USB-1208FS.
2. Run InstaCal.
3. From the PC Board List on the InstaCal main form, double-click on the OM-USB-1208FS you want to use
as a slave. The Board Configuration dialog opens.
4. Select Gated from the Ext. Clock Type drop-down list.
5. Set the Universal Library EXTCLOCK option with cbAInScan()/AInScan for the slave OM-USB-1208FS
to enable pacing from the master USB device.
This InstaCal option does not affect internally paced acquisition. It only affects scans that use the EXTCLOCK option.
An example of a master/slave configuration is shown below.
Figure 13. Configuring for synchronous data acquisition
When you are operating one OM-USB-1208FS, do not set the EXTCLOCK option unless you are using an external clock for A/D pacing.
21
Parameter
Conditions
Specification
A/D converter type
Successive approximation type
Input voltage range for linear operation, single-ended mode
CHx to GND
±10 volts (V) max
Input common-mode voltage range for linear operation, differential mode
CHx to GND
-10 V min, +20 V max
Absolute maximum input voltage
CHx to GND
±28 V max
Input impedance
122KOhm
Input current (Note 1)
Vin = +10 V
70 microamperes (µA) typ
Vin = 0 V
-12 µA typ
Vin = -10 V
-94 µA typ
Number of channels
8 single-ended / 4 differential, software selectable
Input ranges, single-ended mode
±10 V, G=2
Input ranges, differential mode
±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 Software selectable
Throughput (Note 2) Software paced
250 samples per second (S/s) typ, PC-dependent
Continuous scan
50 kilosamples per second (kS/s)
Channel gain queue
Up to 16 elements
Software configurable channel, range, and gain.
Resolution (Note 3) Differential
12 bits, no missing codes
Single-ended
11 bits
CAL accuracy
CAL = 2.5 V
±36.25 mV max
Integral linearity error
±1 least significant bit (LSB) typ
Differential linearity error
±0.5 LSB typ
Repeatability
±1 LSB typ
CAL current Source
5 milliamperes (mA) max
Sink
20 µA min, 100 µA typ
Trigger source
Software selectable
External digital: TRIG_IN
Pacer source
Software selectable
Internal External (SYNC), rising edge triggered Programmed IO

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
Chapter 4
22
Range
Accuracy (LSB)
±20 V
5.1
±10 V
6.1
±5 V
8.1
±4 V
9.1
±2.5 V
12.1
±2 V
14.1
±1.25 V
20.1
±1 V
24.1
Range
Accuracy (LSB)
±10 V
4.0
Range
% of Reading
Gain Error at full scale (FS) (millivolts (mV))
Offset (mV)
Accuracy at FS (mV)
±20 V
0.2
40
9.766
49.766
±10 V
0.2
20
9.766
29.766
±5 V
0.2
10
9.766
19.766
±4 V
0.2 8 9.766
17.766
±2.5 V
0.2 5 9.766
14.766
±2 V
0.2 4 9.766
13.766
±1.25 V
0.2
2.5
9.766
12.266
±1 V
0.2 2 9.766
11.766
Range
% of Reading
Gain Error at FS (mV)
Offset (mV)
Accuracy at FS (mV)
±10 V
0.2
20
19.531
39.531
Range
Typical counts
Least significant bit
root mean square
(LSB
rms)
±20 V
2
0.30
±10 V
2
0.30
±5 V
3
0.45
±4 V
3
0.45
±2.5 V
4
0.61
±2 V
5
0.76
±1.25 V
7
1.06
±1 V
8
1.21
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*Vin-12) µA.
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.
Table 2. Accuracy, differential mode
Table 3. Accuracy, single-ended mode
Table 4. Accuracy components, differential mode - All values are (±)
Table 5. Accuracy components, single-ended mode - All values are (±)
Table 6. Noise performance, differential mode
23
Range
Typical Counts
LSB
rms
±10 V
2
0.30
Parameter
Conditions
Specification
Resolution
12-bits, 1 in 4096
Output range
0 – 4.096 V, 1 mV per LSB.
Number of channels
2
Throughput (Note 4)
Software paced
250 S/s single channel typical, PC dependent
Single channel, continuous scan
10 kS/s
Dual channel, continuous scan, simultaneous update
5 kS/s Power on and reset voltage
Initializes to 000h code
Output drive
Each D/A OUT
15 mA
Slew rate
0.8V/microsecond (µs) typ
Range
Accuracy (LSB)
0-4.096 V
4.0 typ, 45.0 max
Range
% of FSR
Gain Error at FS (mV)
Offset (mV)
(Note 5)
Accuracy at FS (mV)
0-4.096 V
0.1 typ, 0.9 max
4.0 typ, 36.0 max
1.0 typ, 9.0 max
4.0 typ, 45.0 max
Digital type
CMOS
Number of I/O
16 (Port A0 through A7, Port B0 through B7)
Configuration
2 banks of 8
Pull up/pull-down configuration
All pins pulled up to Vs via 47K resistors (default). Positions available for pull down to ground. Hardware selectable via zero ohm (Ω) resistors as a factory option.
Input high voltage
2.0 V min, 5.5 V absolute max
Input low voltage
0.8 V max, –0.5 V absolute min
Output high voltage (IOH = -2.5 mA)
3.8 V min
Output low voltage (IOL = 2.5 mA)
0.7 V max Power on and reset state
Input
Table 7. Noise performance, single-ended mode

Analog output

Table 8. Analog output specifications
Note 4: 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.
Table 10. Analog output accuracy components, all values are (±)
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 input/output

Table 9. Analog output accuracy, all values are (±)
Table 11. Digital I/O specifications
24
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
Input high voltage
4.0 V min, 5.5 V absolute max
Input low voltage
1.0 V max, –0.5 V absolute min
Input leakage current
±1.0 µA
Parameter
Conditions
Specification
Pin name
SYNC
Pin type
Bidirectional
Software selectable direction Output (default)
Outputs internal A/D pacer clock.
Input
Receives A/D pacer clock from external source.
Input clock rate
50 KHz, maximum
Clock pulse width Input mode
1 µs min
Output mode
5 µs min
Input leakage current
Input mode
±1.0 µA
Input high voltage
4.0 V min, 5.5 V absolute max
Input low voltage
1.0 V max, –0.5 V absolute min
Output high voltage (Note 7) IOH = -2.5 mA
3.3 V min
No load
3.8 V min
Output low voltage (Note 7) IOL = 2.5 mA
1.1 V max
No load
0.6 V max
Pin name (Note 8)
CTR
Counter type
Event counter
Number of channels
1
Input type
TTL, rising edge triggered
Input source
CTR screw terminal
Resolution
32 bits
Schmidt trigger hysteresis
20 mV to 100 mV
Input leakage current
±1 µA
Maximum input frequency
1 MHz
High pulse width
500 ns min
Low pulse width
500 ns min
Input high voltage
4.0 V min, 5.5 V absolute max

External trigger

Table 12. Digital trigger specifications
Note 6: TRIG_IN is a Schmitt trigger input protected with a 1.5 kilohm (kΩ) series resistor.

External clock input/output

Table 13. External clock I/O specifications
Note 7: SYNC is a Schmitt trigger input and is over-current protected with a 200 Ω series resistor.

Counter

Table 14. Counter specifications
25
Input low voltage
1.0 V max, –0.5 V absolute min
EEPROM
1,024 bytes
EEPROM Configuration
Address Range
Access
Description
0x000-0x07F
Reserved
128 bytes system data
0x080-0x1FF
Read/write
384 bytes cal data
0x200-0x3FF
Read/write
512 bytes user area
Type
High performance 8-bit RISC microcontroller
Program Memory
16,384 words
Data Memory
2,048 bytes
Parameter
Conditions
Specification
Supply current (Note 9)
80 mA
+5V USB power available (Note 10) Connected to self-powered hub Connected to externally-powered root port hub
4.5 V min, 5.25 V max Connected to bus-powered hub
4.1 V min, 5.25 V max
Output current (Note 11) Connected to self-powered hub Connected to externally-powered root port hub
420 mA max Connected to bus-powered hub
20 mA max
Note 8: CTR is a Schmitt trigger input protected with a 1.5K Ω series resistor.

Non-volatile memory

Table 15. Non-volatile memory specifications

Microcontroller

Table 16. Microcontroller specifications

Power

Note 9: This is the total current requirement for the OM-USB-1208FS which includes up to 10 mA for
Note 10: Self-powered hub refers to a USB hub with an external power supply. Self-powered hubs allow
Table 17. Power specifications
the status LED.
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 11: This refers to the total amount of current that can be sourced from the USB +5 V, analog outputs
and digital outputs.
26
Parameter
Conditions
Specification
Device type
USB 2.0 full speed
Device compatibility
USB 1.1, USB 2.0
Operating temperature range
0 to 70 °C
Storage temperature range
-40 to 70 °C
Humidity
0 to 90% non-condensing
Dimensions
79 millimeters (mm) long x 82 mm wide x 25 mm high
USB cable length
3 meters max
User connection length
3 meters max
Connector type
Screw terminal
Wire gauge range
16 AWG to 30 AWG
Pin
Signal Name
Pin
Signal Name
1
CH0 IN HI
21
Port A0
2
CH0 IN LO
22
Port A1
3
AGND
23
Port A2
4
CH1 IN HI
24
Port A3
5
CH1 IN LO
25
Port A4
6
AGND
26
Port A5
7
CH2 IN HI
27
Port A6
8
CH2 IN LO
28
Port A7
9
AGND
29
GND
10
CH3 IN HI
30
PC+5V
11
CH3 IN LO
31
GND
12
AGND
32
Port B0
13
D/A OUT 0
33
Port B1
14
D/A OUT 1
34
Port B2
15
AGND
35
Port B3
16
CAL
36
Port B4
17
GND
37
Port B5
18
TRIG_IN
38
Port B6
19
SYNC
39
Port B7
20
CTR
40
GND

General

Table 18. General specifications

Environmental

Table 19. Environmental specifications

Mechanical

Table 20. Mechanical specifications

Main connector and pin out

Table 21. Main connector specifications

4-channel differential mode

27
Pin
Signal Name
Pin
Signal Name
1
CH0 IN
21
Port A0
2
CH1 IN
22
Port A1
3
AGND
23
Port A2
4
CH2 IN
24
Port A3
5
CH3 IN
25
Port A4
6
AGND
26
Port A5
7
CH4 IN
27
Port A6
8
CH5 IN
28
Port A7
9
AGND
29
GND
10
CH6 IN
30
PC+5V
11
CH7 IN
31
GND
12
AGND
32
Port B0
13
D/A OUT 0
33
Port B1
14
D/A OUT 1
34
Port B2
15
AGND
35
Port B3
16
CAL
36
Port B4
17
GND
37
Port B5
18
TRIG_IN
38
Port B6
19
SYNC
39
Port B7
20
CTR
40
GND

8-channel single-ended mode

28
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