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OM-USB-1608FS
User guide
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Omega OM-USB-1608FS User guide

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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-1608FS ........................................................................................................ 6
OM-USB-1608FS block diagram ....................................................................................................................... 7
Software features ................................................................................................................................................ 7
Connecting a OM-USB-1608FS to your computer is easy ................................................................................. 8
Chapter 2
Installing the OM-USB-1608FS ............................................................................................................ 9
What comes with your OM-USB-1608FS shipment?......................................................................................... 9
Hardware .......................................................................................................................................................................... 9
Additional documentation ................................................................................................ ................................................. 9
Unpacking the OM-USB-1608FS ....................................................................................................................... 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
Burst scan mode ...............................................................................................................................................................11
External components ........................................................................................................................................ 12
USB connector .................................................................................................................................................................12
LED .................................................................................................................................................................................12
Screw terminal wiring ......................................................................................................................................................13
Main connector and pin out .............................................................................................................................................13
Analog input terminals (CH0 IN - CH7 IN).....................................................................................................................14
Digital I/O terminals (DIO0 to DIO7)..............................................................................................................................14
Power terminals ...............................................................................................................................................................15
Ground terminals .............................................................................................................................................................15
Calibration terminal .........................................................................................................................................................15
Counter terminal ..............................................................................................................................................................16
SYNC terminal ................................................................................................................................................................16
Trigger terminal ................................................................................................................................ ...............................16
Accuracy ........................................................................................................................................................... 16
Gain queue ........................................................................................................................................................ 19
Synchronizing multiple units ............................................................................................................................ 19
Chapter 4
Specifications ...................................................................................................................................... 21
Analog input section ......................................................................................................................................... 21
Digital input/output........................................................................................................................................... 22
External trigger ................................................................................................................................................. 22
External clock input/output............................................................................................................................... 23
Counter section ................................................................................................................................................. 23
Memory ............................................................................................................................................................ 23
Microcontroller ................................................................................................................................................. 24
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Power ................................................................................................................................ ................................ 24
General ............................................................................................................................................................. 24
Environmental .................................................................................................................................................. 24
Mechanical ....................................................................................................................................................... 24
Main connector and pin out .............................................................................................................................. 25
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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-1608FS 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.
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Chapter 1

Introducing the OM-USB-1608FS

This user's guide contains all of the information you need to connect the OM-USB-1608FS to your computer and to the signals you want to measure. The OM-USB-1608FS is part of the Measurement Computing brand of USB-based data acquisition products.
The OM-USB-1608FS 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-1608FS offers true simultaneous sampling of up to eight channels of 16-bit single-ended analog input. This is accomplished through the use of one A/D converter per channel. The range of each channel is independently configurable via software. Eight digital IO lines are independently selectable as input or output. A 32-bit counter is capable of counting TTL pulses. The OM-USB-1608FS is powered by the +5 volt USB supply from your computer. No external power is required.
A SYNC (synchronization) control line allows you to synchronize two OM-USB-1608FS modules together to acquire data synchronously from 16 analog inputs.
The OM-USB-1608FS is shown in Figure 1. I/O connections are made to the screw terminals located along each side of the OM-USB-1608FS.
Figure 1. OM-USB-1608FS
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OM-USB-1608FS block diagram

OM-USB-1608FS functions are illustrated in the block diagram shown here.
Figure 2. OM-USB-1608FS Functional Block Diagram

Software features

For information on the features of InstaCal and the other software included with your OM-USB-1608FS, refer to the OMB-DAQ-2416 Series and OM-USB Series Data Acquisition Software User’s Guide that shipped with your device.
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Connecting a OM-USB-1608FS to your computer is easy

Installing a data acquisition device has never been easier. The OM-USB-1608FS 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-1608FS. No third-party device driver is required.
The OM-USB-1608FS is plug-and-play. There are no jumpers to position, DIP switches to set, or interrupts
to configure.
You can connect the OM-USB-1608FS 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-1608FS 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.
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Installing the OM-USB-1608FS

What comes with your OM-USB-1608FS shipment?

The following items are shipped with the OM-USB-1608FS.

Hardware

OM-USB-1608FS
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-1608FS and information regarding installation of that software. Please read this booklet completely before installing any software or hardware.

Unpacking the OM-USB-1608FS

As with any electronic device, you should take care while handling to avoid damage from static electricity. Before removing the OM-USB-1608FS 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
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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-1608FS.

Installing the hardware

Be sure you are using the latest system software
Before you install your OM-USB-1608FS, run Windows Update to update your operating system with the latest HID and USB drivers.
To connect the OM-USB-1608FS 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-1608FS.
The OM-USB-1608FS installs as a composite device with separate devices attached. When you connect the OM-USB-1608FS for the first time, Found New Hardware popup balloons (Windows XP) or dialogs (other Windows version) open as each OM-USB-1608FS interface is detected. It is normal for multiple dialogs to open when you connect the OM-USB-1608FS for the first time.
When the last balloon or dialog closes, the installation is complete. The LED on the OM-USB-1608FS should flash and then remain lit. This indicates that communication is established between the OM-USB-1608FS and your computer.
Caution! Do not disconnect any device from the USB bus while the computer is communicating with the
OM-USB-1608FS, or you may lose data and/or your ability to communicate with the OM-USB­1608FS.
If the LED turns off
If the LED is lit but then turns off, the computer has lost communication with the OM-USB-1608FS. 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-1608FS can acquire analog input data in three basic modes – software paced, continuous scan, and burst scan.

Software paced mode

You can acquire one analog sample at a time in software paced mode. You initiate the A/D conversion by calling a software command. The analog value is converted to digital data 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

You can acquire data from up to eight channels simultaneously in continuous scan mode. The analog data is continuously acquired, converted to digital values, and written to an on-board FIFO buffer on the OM-USB­1608FS until you stop the scan. The FIFO buffer is serviced in blocks as the data is transferred from the OM­USB-1608FS FIFO buffer to the memory buffer on your computer.
The maximum sampling rate is an aggregate rate, where the total sample rate for all channels is 100 kS/s divided by the number of channels, with a maximum rate of 50 kS/s for any channel. Using this equation, you can acquire data with the OM-USB-1608FS from one channel at 50 kS/s, two channels at 50 kS/s each, four channels at 25 kS/s each, and so on, up to eight channels at 12.5 kS/s each. You can start a continuous scan with either a software command or with an external hardware trigger event.

Burst scan mode

In burst scan mode, you can acquire data with the OM-USB-1608FS using the full capacity of its 32 K sample FIFO. The acquired data is then read from the FIFO and transferred to a user buffer in your computer. You can initiate a single acquisition sequence of one, two, four, or eight channels by either a software command or an external hardware trigger.
Burst scans are limited to the depth of the on-board memory, as the data is acquired at a rate faster than it can be transferred to the computer. The maximum sampling rate is an aggregate rate, where the total acquisition rate for all channels is 200 kS/s divided by the number of channels, with a maximum rate of 50 kS/s for any channel. The maximum rate that you can acquire data using burst scan mode is 50 kS/s each for one, two, or four channels, and 25 kS/s each for eight channels.
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When the LED is…
It indicates…
Steady green
The OM-USB-1608FS is connected to a computer or external USB hub.
Blinks continuously
Data is being transferred.
Blinks three times
Initial communication is established between the OM-USB-1608FS and the computer.
Blinks at a slow rate
The analog input is configured for external trigger. The LED stops blinking and illuminates steady green when the trigger is received.

External components

The OM-USB-1608FS has the following external components, as shown in Figure 3.
USB connector LED Screw terminal banks (2)
Figure 3. OM-USB-1608FS

USB connector

The USB connector is on the right side of the OM-USB-1608FS. 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 OM-USB-1608FS indicates the communication status. It uses up to 5 mA of current and cannot be disabled. The table below explains the function of the OM-USB-1608FS LED.
LED Illumination
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Connector type
Screw terminal
Wire gauge range
16 AWG to 30 AWG

Screw terminal wiring

The OM-USB-1608FS 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-1608FS screw terminal pin numbers
Screw terminal – pins 1-20
The screw terminals on the top edge of the OM-USB-1608FS (pins 1 to 20) provide the following connections:
Eight analog input connections (CH0 IN to CH7 IN) Eleven analog ground connections (AGND) One calibration output terminal (CAL)
Screw terminal – pins 21-40
The screw terminals on the bottom edge of the OM-USB-1608FS (pins 21 to 40) provide the following connections:
Eight digital I/O connections (DIO0 to DIO7) One external trigger source (TRIG_IN) One external event counter connection (CTR) One power connection (PC+5 V) One SYNC terminal for external clocking and multi-unit synchronization (SYNC) Eight ground connections (GND)

Main connector and pin out

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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 diagram above for the location of these pins. We recommend that you connect unused analog input terminals to ground terminals during operation. For example, if you are not using terminal 15 (CH7 IN), connect this terminal to terminal 16 (AGND).
Input configuration
All of the analog input channels are configured for single-ended input mode. Each analog signal is referenced to signal ground (AGND), and requires two wires:
The wire carrying the signal to be measured connects to CH# IN. The second wire connects to AGND.
The input voltage ranges are ±10 V, ±5 V, ±2.0 V, ±1.0 V.
For more information on analog signal connections
For more information on single-ended inputs, refer to the 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).

Digital I/O terminals (DIO0 to DIO7)

You can connect up to eight digital I/O lines to the screw terminal containing pins 21 to 40 (DIO0 to DIO7). Refer to the pinout diagram above for the location of these pins. You can configure each digital bit for either input or output. All digital I/O lines are pulled up to USB +5 V with a 47 K resistor (default). You can request the factory to configure the resistor for pull-down to ground if desired.
When you configure the digital bits for input, you can use the OM-USB-1608FS digital I/O terminals to detect the state of any TTL-level input. Refer to the schematic shown in Figure 5. If you set the switch to the +5 V input, DIO0 reads TRUE (1). If you move the switch to GND, DIO0 reads FALSE (0).
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Figure 5. Schematic showing switch detection by digital channel DIO0
For more information on digital signal connections
For general information regarding digital signal connections and digital I/O techniques, refer to the Guide to Signal Connections (available on our web site at www.mccdaq.com/signals/signals.pdf).

Power terminals

The PC +5 V connection (pin 39) is on the bottom screw terminal of the OM-USB-1608FS. Refer to the pinout diagram on page 14 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 computer.
Caution! The +5 V terminal is an output. Do not connect to an external power supply or you may damage
the OM-USB-1608FS and possibly the computer.
The maximum total output current that can be drawn from all OM-USB-1608FS connections (power, analog, and digital outputs) is 500 mA. This maximum applies to most personal computers and self-powered USB hubs. Bus-powered hubs and notebook computers may limit the maximum available output current to 100 mA.
The OM-USB-1608FS alone draws 150 mA of current from the USB +5 V supply. Once you start running applications with the OM-USB-1608FS, each DIO bit can draw up to 2.5 mA. The maximum amount of +5 V current available for experimental use, over and above that required by the OM-USB-1608FS, is the difference between the total current requirement of the OM-USB-1608FS (based on the application), and the allowed current draw of the computer platform (500 mA for desktop computers and self-powered hubs).
With all outputs at their maximum output current, you can calculate the total current requirement of the OM­USB-1608FS USB +5 V as follows:
(OM-USB-1608FS @ 150 mA) + (8 DIO @ 2.5 mA ea) = 170 mA
For an application running on a computer or powered hub, the maximum available excess current is 500 mA − 170 mA = 330 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 250­300 mA range.
Since some laptop computers running on battery power only allow up to 100 mA, the OM-USB-1608FS may be above that allowed by the computer. In this case, you must either purchase a self-powered hub or operate the laptop computer from an external power adapter.

Ground terminals

The 11 analog ground connections provide a common ground for all OM-USB-1608FS input channels. Eight ground connections provide a common ground for the DIO, TRIG_IN, CTR, SYNC and PC +5 V connections. Refer to the pinout diagram on page 14 for the location of the AGND and GND terminal pins.

Calibration terminal

The CAL connection (pin 17) is an output you should use only to calibrate the OM-USB-1608FS. Refer to the pinout diagram on page 14 for the location of this pin. Calibration of the OM-USB-1608FS is software­controlled by InstaCal.
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Counter terminal

The CTR connection (pin 38) is a TTL-level input to a 32-bit event counter. Refer to the pinout diagram on page 14 for the location of this pin. The internal counter increments when the TTL level transitions from low to high. The counter can count frequencies of up to 1 MHz.

SYNC terminal

The SYNC connection (pin 36) 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 OM-USB-1608FS and acquire data from 16 channels. Refer to the pinout diagram on page 14 for the location of this pin. For more information about synchronizing
multiple units, refer to page 19.

Trigger terminal

The TRIG_IN connection (pin 37) is an external digital trigger input. You can configure this terminal with software for either rising or falling edge.

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 "16-bits" or "1 part in 65536" does indicate what can be resolved, it provides little insight into the quality, or accuracy, of an absolute measurement. Accuracy specifications describe the actual measurement that can be relied upon with a OM-USB-1608FS.
There are three types of errors which affect the accuracy of a measurement system:
offset gain nonlinearity
The primary error sources in the OM-USB-1608FS are offset and gain. Nonlinearity is small in the OM-USB­1608FS, and is not significant as an error source with respect to offset and gain.
Figure 6 shows an ideal, error-free, OM-USB-1608FS transfer function. The typical calibrated accuracy of the OM-USB-1608FS is range-dependent, as explained in the "Specifications" chapter on page 21. We use a ±10 V range as an example of what you can expect when performing a measurement in this range.
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Figure 6. Ideal ADC transfer function
The OM-USB-1608FS offset error is measured at mid-scale. Ideally, a zero volt input should produce an output code of 32768. Any deviation from this is an offset error. Figure 7 shows the OM-USB-1608FS transfer function with an offset error. The typical offset error specification for the OM-USB-1608FS on the ±10 V range is ±1.66 mV. Offset error affects all codes equally by shifting the entire transfer function up or down along the input voltage axis.
The accuracy plots in Figure 7 are drawn for clarity and are not drawn to scale.
Figure 7. 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 8 shows the OM-USB-1608FS transfer function with gain error. Gain error is easily converted to voltage by multiplying the full-scale input (±10 V) by the error.
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The accuracy plots in Figure 8 are drawn for clarity and are not drawn to scale.
Figure 8. ADC Transfer function with gain error
For example, the OM-USB-1608FS exhibits a typical calibrated gain error of ±0.04% on all ranges. For the ±10 V range, this would yield 10 V × ±0.0002 = ±4 mV. This means that at full scale, neglecting the effect of offset for the moment, the measurement would be within 4 mV of the actual value. Note that gain error is expressed as a ratio. Values near ±FS (±10 V) are more affected from an absolute voltage standpoint than are values near mid-scale, which see little or no voltage error.
Combining these two error sources in Figure 9, we have a plot of the error band of the OM-USB-1608FS at ±full scale (±10 V). This plot is a graphical version of the typical accuracy specification of the product.
The accuracy plots in Figure 9 are drawn for clarity and are not drawn to scale.
Figure 9. Error band plot
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Element
Channel
Range
0
CH0
BIP10V
1
CH1
BIP5V
2
CH2
BIP10V
3
CH3
BIP1V
4
CH4
BIP2V
5
CH5
BIP10V
6
CH6
BIP1V
7
CH7
BIP5V

Gain queue

The OM-USB-1608FS gain queue allows you to set up a different gain setting for each channel. The gain queue removes the restriction of having a single gain for all channels. This feature creates a gain list which is written to local memory on the OM-USB-1608FS. The gain list is made up of a channel number and range setting. An example of an eight-element list is shown in the table below.
Sample channel gain queue list
Note that the gain queue must contain eight elements that include all eight channels. 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-1608FS, it does produce a useless full-scale reading. It can also introduce a long recovery time due to saturation of the input channel.

Synchronizing multiple units

You can run up to two OM-USB-1608FS units on most computers.
You can connect the SYNC pin of two OM-USB-1608FS units together in a master/slave configuration and acquire data synchronously from 16 channels. 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 OM­USB-1608FS configured for A/D pacer input.
Change to SYNC pin setting not implemented until first scan
When you change the setting of the SYNC pin to input or to output using InstaCal, the change does not take place until you run a scan with the OM-USB-1608FS.
Consequently, if you change the SYNC pin from output to input, the SYNC pin remains an output, and connections to this pin are connections to an output, until the first scan runs. This will not damage the OM­USB-1608FS.
To update the SYNC pin setting before making connections to the SYNC pin, run InstaCal's analog Scan Test.
To synchronize a master OM-USB-1608FS with a slave OM-USB-1608FS and acquire data from 16 channels, follow the steps below:
1. Run InstaCal.
2. Double-click on the OM-USB-1608FS listing on the PC Board List on the InstaCal main form. The Board
Configuration dialog displays.
3. Configure the SYNC pin of the master OM-USB-1608FS for pacer output:
o Double-click on the OM-USB-1608FS that you want to configure as the master. The Board
Configuration dialog opens.
o Click to select the Enable Sync output check box and then click OK.
4. Configure the SYNC pin of the slave OM-USB-1608FS for pacer input:
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o Double-click on the OM-USB-1608FS that you want to configure as the slave. The Board
Configuration dialog displays.
o Make sure that the Enable Sync output check box is not checked (unchecked is the default setting).
5. Connect the SYNC pin on the master OM-USB-1608FS to the SYNC pin on the slave OM-USB-1608FS.
6. Set the Universal Library EXTCLOCK option with cbAInScan()/AInScan() for the slave OM-USB-
1608FS to enable pacer output.
An example of a master/slave configuration is shown below.
Figure 10. Configuring for synchronous data acquisition
When you are operating one OM-USB-1608FS, do not set the EXTCLOCK option unless you are using an external clock for A/D pacing.
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Parameter
Conditions
Specification
A/D converter type
16-bit successive Approximation type
Number of channels
8 single-ended
Input configuration
Individual A/D per channel
Sampling method
Simultaneous
Absolute maximum input voltage
CHx IN to GND.
±15 V max
Input impedance
100 MOhm, min
Input ranges
Software selectable
±10 V, ±5 V, ±2 V, ±1 V
Sampling rate
Scan to PC memory
0.6 S/s to 50 kS/s, software programmable
Burst scan to 32 k sample FIFO
20 S/s to 50 kS/s, software programmable
Throughput
Software paced
500 S/s all channels
Scan to PC memory (Note 1)
= (100 kS/s) / (# of channels), max of 50 kS/s for any channel
Burst scan to 32 k sample FIFO
= (200 kS/s) / (# of channels), max of 50 kS/s for any channel
Gain queue
Software configurable. Eight elements, one gain element per channel.
Resolution
16 bits
No missing codes
15 bits
Crosstalk
Signal DC-25 KHz
-80 dB
CAL output
User calibration source
0.625 V, 1.25 V, 2.5 V, 5.0 V, software selectable
CAL output accuracy (Note 2)
±0.5% typ, ±1.0% max
CAL current
±5 mA max
Trigger source
Software selectable
External digital: TRIG_IN
Range
Accuracy (mV)
±10 V
5.66
±5 V
2.98
±2 V
1.31
±1 V
0.68

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 section

Table 1. Analog input specifications
Chapter 4
Note 1: Maximum throughput scanning to PC memory is machine dependent. While the majority of XP
Note 2: Actual values used for calibration are measured and stored in EEPROM.
equipped PC’s we tested allowed acquisition at the maximum rates, a few would not. The lowest
maximum rate we observed on an XP equipped PC during multi-channel testing was 95 kS/s, aggregate. 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 2. Calibrated absolute accuracy
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Range
% of Reading
Gain error at FS (mV)
Offset (mV)
±10 V
0.04
4.00
1.66
±5 V
0.04
2.00
0.98
±2 V
0.04
0.80
0.51
±1 V
0.04
0.40
0.28
Range
Typical counts
LSBrms
±10 V
10
1.52
±5 V
10
1.52
±2 V
11
1.67
±1 V
14
2.12
Digital type
CMOS
Number of I/O
8 (DIO0 through DIO7)
Configuration
Independently configured for input or output
Pull-up/pull-down configuration
All pins pulled up to Vs via 47 K resistors (default). Positions available for pull down to ground. Hardware selectable via zero ohm 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
Parameter
Conditions
Specification
Trigger source (Note 3)
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
1µs 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
±1.0µA
Table 3. Accuracy components - All values are (±)
Table 4 summarizes the noise performance for the OM-USB-1608FS. Noise distribution is determined by gathering 50 K samples with inputs tied to ground at the user connector. Samples are gathered at the maximum specified sampling rate of 50 kS/s.
Table 4. Noise performance

Digital input/output

External trigger

Table 5. Digital I/O specifications
Table 6. External trigger specifications
Note 3: TRIG_IN is a Schmitt trigger input protected with a 1.5K Ohm series resistor.
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Parameter
Conditions
Specification
Pin name
SYNC
Pin type
Bidirectional
Software selectable direction Output
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
1µs min
Output
5µs min
Input leakage current
±1.0µA
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 4) IOH = –2.5 mA
3.3 V min
No load
3.8 V min
Output low voltage (Note 4) IOL = 2.5 mA
1.1 V max
No Load
0.6 V max
Pin name (Note 5)
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
±1µA
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
Input low voltage
1.0 V max, –0.5 V absolute min
Data FIFO
32,768 samples, 65,536 bytes
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

External clock input/output

Table 7. External clock I/O specifications
Note 4: SYNC is a Schmitt trigger input and is over-current protected with a 200 Ohm series resistor.

Counter section

Note 5: CTR is a Schmitt trigger input protected with a 1.5K Ohm series resistor.

Memory

Table 8. Counter specifications
Table 9. Memory specifications
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Type
High performance 8-bit RISC microcontroller
Program memory
16,384 words
Data memory
2,048 bytes
Parameter
Conditions
Specification
Supply current
USB enumeration
< 100 mA
Supply current (Note 6)
Continuous mode
150 mA
+5 V USB power available (Note 7)
Connected to self-powered hub Connected to externally-powered root port hub
4.5 V min, 5.25 V max Output current (Note 8)
350 mA max
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 mm (L) x 82 mm (W) x 25 mm (H)
USB cable length
3 meters max
User connection length
3 meters max

Microcontroller

Table 10. Microcontroller specifications

Power

Note 6: This is the total current requirement for the OM-USB-1608FS 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 PC’s) 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. If your laptop PC is constrained to the 100 mA maximum, you need to purchase a self-powered hub.
Note 8: This refers to the total amount of current that can be sourced from the USB +5 V and digital
outputs.

General

Environmental

Mechanical

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Connector type
Screw terminal
Wire gauge range
16 AWG to 30 AWG
Pin
Signal Name
Pin
Signal Name
1
CH0 IN
21
DIO0
2
AGND
22
GND
3
CH1 IN
23
DIO1
4
AGND
24
GND
5
CH2 IN
25
DIO2
6
AGND
26
GND
7
CH3 IN
27
DIO3
8
AGND
28
GND
9
CH4 IN
29
DIO4
10
AGND
30
GND
11
CH5 IN
31
DIO5
12
AGND
32
GND
13
CH6 IN
33
DIO6
14
AGND
34
GND
15
CH7 IN
35
DIO7
16
AGND
36
SYNC
17
CAL
37
TRIG_IN
18
AGND
38
CTR
19
AGND
39
PC +5V
20
AGND
40
GND

Main connector and pin out

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