Measurement Computing USB-2416-4AO User manual

USB-2416-4AO
USB-based 24-bit, Isolated, High-Channel-Count Multifunction DAQ Device with 4 Analog Outputs
Document Revision 5A
May 2013
© Copyright 2013
User's Guide

HM USB-2416-4AO
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photocopying, recording, or otherwise without the prior written permission of Measurement Computing
Corporation.
Notice
Measurement Computing Corporation does not authorize any Measurement Computing Corporation product for
use in life support systems and/or devices without prior written consent from Measurement Computing
Corporation. Life support devices/systems are devices or systems that, a) are intended for surgical implantation
into the body, or b) support or sustain life and whose failure to perform can be reasonably expected to result in
injury. Measurement Computing Corporation products are not designed with the components required, and are
not subject to the testing required to ensure a level of reliability suitable for the treatment and diagnosis of
people.

3
Table of Contents
Preface
About this User's Guide .......................................................................................................................5
What you will learn from this user's guide.........................................................................................................5
Conventions in this user's guide .........................................................................................................................5
Where to find more information.........................................................................................................................5
Chapter 1
Introducing the USB-2416-4AO ...........................................................................................................6
Overview: USB-2416-4AO features...................................................................................................................6
Functional block diagram...................................................................................................................................6
Chapter 2
Installing the USB-2416-4AO................................................................................................................7
What comes with your USB-2416-4AO shipment?............................................................................................7
Hardware .......................................................................................................................................................................... 7
Software............................................................................................................................................................................ 7
Documentation.................................................................................................................................................................. 7
Optional components........................................................................................................................................................ 7
Unpacking...........................................................................................................................................................7
Installing the software ........................................................................................................................................8
Installing the hardware .......................................................................................................................................8
Connecting to an AI-EXP32 with the DSUB37 expansion connector................................................................8
Configuring the hardware...................................................................................................................................9
Connecting the board for I/O operations ............................................................................................................9
Connectors, cables – main I/O connector.......................................................................................................................... 9
Screw terminal pin out – differential ...............................................................................................................................10
Screw terminal pin out – single-ended.............................................................................................................................11
Chapter 3
Functional Details ...............................................................................................................................12
USB-2416-4AO components............................................................................................................................12
LEDs................................................................................................................................................................................13
USB connector.................................................................................................................................................................13
External power connector................................................................................................................................................13
Screw terminal wiring ......................................................................................................................................13
Analog/TC input terminals ...............................................................................................................................13
Analog input mode...........................................................................................................................................................14
Thermocouple inputs .......................................................................................................................................................14
Noise filtering, data rate, and throughput rate..................................................................................................................15
Multiple-channel throughput rates...................................................................................................................................16
Input isolation...................................................................................................................................................16
Analog output terminals (VDAC0 through VDAC3).......................................................................................17
Digital I/O.........................................................................................................................................................17
Internal pull-up/pull-down capability...............................................................................................................................18
External pull-up/pull-down capability .............................................................................................................................19
Counter input terminals (CTR0, CTR1)...........................................................................................................19
USB-2416-4AO mechanical drawings .............................................................................................................20
Chapter 4
Calibrating the USB-2416-4AO...........................................................................................................21
Calibration methods..........................................................................................................................................21

USB-2416-4AO User's Guide
4
Factory calibration...........................................................................................................................................................21
Self calibration.................................................................................................................................................................21
Chapter 5
Specifications......................................................................................................................................22
Analog input .....................................................................................................................................................22
Channel configurations.....................................................................................................................................23
Compatible sensors..........................................................................................................................................................23
Accuracy...........................................................................................................................................................23
Thermocouple measurement accuracy.............................................................................................................................23
Analog input DC voltage measurement accuracy............................................................................................................32
Input bandwidth...............................................................................................................................................................34
Noise performance...........................................................................................................................................................34
Channel switching error...................................................................................................................................................35
Throughput rate ................................................................................................................................................36
Analog voltage output ......................................................................................................................................37
Analog input/output calibration........................................................................................................................38
Digital input/output...........................................................................................................................................38
Counter.............................................................................................................................................................39
Memory ............................................................................................................................................................39
Microcontroller.................................................................................................................................................39
Power................................................................................................................................................................40
USB specifications ...........................................................................................................................................40
Environmental ..................................................................................................................................................40
Mechanical .......................................................................................................................................................41
Screw terminal connector type and pin-out ......................................................................................................41
Screw terminal pin out.....................................................................................................................................................42
Optional AI-EXP32 expansion module............................................................................................................44
AI-EXP32 screw terminal pin out....................................................................................................................................46
USB-2416-4AO screw terminal pin out (with AI-EXP32 attached)................................................................................48
Declaration of Conformity..................................................................................................................49

5
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-2416-4AO so that you get the most out of
its analog I/O, thermocouple (TC) input, digital I/O, and counter/timer I/O features.
Conventions in this user's guide
For more information
Text presented in a box signifies additional information and helpful hints related to the subject matter you are
reading.
Caution! Shaded caution statements present information to help you avoid injuring yourself and others,
damaging your hardware, or losing your data.
bold text Bold text is used for the names of objects on a screen, such as buttons, text boxes, and check boxes.
italic text Italic text is used for the names of manuals and help topic titles, and to emphasize a word or phrase.
Where to find more information
Additional information about the USB-2416-4AO is available on our website at www.mccdaq.com. You can
also contact Measurement Computing Corporation by phone, fax, or email with specific questions.
Knowledgebase: kb.mccdaq.com
Phone: [phone] and follow the instructions for reaching Tech Support
Fax: [phone] to the attention of Tech Support
Email: [e-mail]

6
Chapter 1
Introducing the USB-2416-4AO
Overview: USB-2416-4AO features
is a multifunction measurement and control board designed for the USB bus.
The USB-2416-4AO is a full-speed (up to1 kS/s), multiplexed 24-bit measurement system that provides up to
16 differential and up to 32 single-ended (SE) analog inputs. It offers software-selectable analog input ranges of
±20 V, ±10 V, ±5 V, ±2.5 V, ±1.25 V, ±0.625 V, ±0.312 V, ±0.156 V, and ±0.078 V.
It also protects your computer by providing a minimum of 500 VDC input isolation between field wiring and
the USB interface.
You can configure up to 16 of the analog inputs as differential thermocouple (TC) inputs. In thermocouple
mode, the USB-2416-4AO includes built-in cold-junction compensation and open thermocouple detection.
You can add up to 32 single-ended or up to 16 differential channels by connecting the USB-2416-4AO to an
AI-EXP32 expansion module. Each channel is software-configurable as single-ended or differential. For each
channel pair configured differentially, you lose one SE channel.
The USB-2416-4AO has four 16-bit analog output channels with an update rate of up to1 kS/s and an output
range of ±10 V.
The device has eight lines of digital I/O and two 32-bit counters. You can expand up to 24 DIO channels by
connecting the USB-2416-4AO to an AI-EXP32 expansion module.
Six banks of removable screw-terminal blocks provide connectivity to the analog input channels, digital I/O
lines, counter/timer channels, and analog outputs.
Functional block diagram
USB-2416-4AO functions are illustrated in the block diagram shown here.
Figure 1. Functional block diagram

7
Chapter 2
Installing the USB-2416-4AO
What comes with your USB-2416-4AO shipment?
As you unpack your USB-2416-4AO, verify that the following components are included.
Hardware
 USB-2416-4AO
 USB cable (2-meter length)
 PS-5V2AEPS - 10 Watt regulated power supply plugs into the external power connector of the
USB-2416-4AO.
Software
 MCC DAQ CD
Documentation
In addition to this hardware user's guide, you should also receive the Quick Start Guide. This booklet provides
an overview of the MCC DAQ software you received with the device, and includes information about installing
the software. Please read this booklet completely before installing any software or hardware.
Optional components
Expansion devices that are compatible with the USB-2416-4AO must be ordered separately. If you ordered the
following product with your device, it should be included with your shipment.
AI-EXP32
Analog input expansion module adds up to 16 differential or 32 single-ended inputs to the USB-2416-4AO.
ACC-202 Din-rail kit
Accessory for mounting a USB-2416-4AO to a standard DIN rail. Use the thread-forming screws to attach the
DIN rail clip to your device.
Unpacking
As with any electronic device, you should take care while handling to avoid damage from static
electricity. Before removing the USB-2416-4AO 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 Measurement Computing Corporation immediately by
phone, fax, or e-mail:
 Knowledgebase: kb.mccdaq.com
 Phone: [phone] and follow the instructions for reaching Tech Support
 Fax: [phone] to the attention of Tech Support
 Email: [e-mail]
For international customers, contact your local distributor. Refer to the International Distributors section on our
website at www.mccdaq.com/International.
Thread-forming
screws

USB-2416-4AO User's Guide Installing the USB-2416-4AO
8
Installing the software
Refer to the Quick Start Guide for instructions on installing the software on the MCC DAQ CD. This booklet is
available in PDF at www.mccdaq.com/PDFmanuals/DAQ-Software-Quick-Start.pdf.
Installing the hardware
To connect the USB-2416-4AO to your system, turn your computer on, and then do the following:
1. Connect the PS-5V2AEPS power supply to the USB-2416-4AO's external power connector, and plug the
other end into a power outlet.
2. Connect the USB cable to the USB-2416-4AO USB connector and to a USB port on your computer. A
USB2.0 port is recommended.
When you connect the USB-2416-4AO to a computer for the first time, a Found New Hardware dialog opens
when the operating system detects the device. When the message closes, the installation is complete.
The power LED (bottom LED) blinks during device detection and initialization, and then remains solid if
properly detected. If not, check if the USB-2416-4AO has sufficient power. When the device is first powered
on, there is usually a momentary delay before the power LED begins to blink, or come on solid.
Caution! Do not disconnect any device from the USB bus while the computer is communicating with the
USB-2416-4AO, or you may lose data and/or your ability to communicate with the
USB-2416-4AO.
Connecting to an AI-EXP32 with the DSUB37 expansion connector
Use the 37-pin expansion connector to connect the USB-2416-4AO to an AI-EXP32 expansion module.
To connect the two devices directly to each other, follow these steps.
1. Disconnect the USB cable from the USB-2416-4AO.
2. Remove the external power cable from the USB-2416-4AO.
3. Connect the two devices together by inserting the AI-EXP32 DSUB37 connector into the DSUB37
connector on the USB-2416-4AO.
Figure 2. USB-2416-4AO directly connected to an AI-EXP32
4. Turn the connected modules over and secure the connection by screwing the connection plate to both
modules, as shown below.
Figure 3. USB-2416-4AO secured to an AI-EXP32
5. Connect the external power supply to the power input port of the USB-2416-4AO, and then plug it into an
AC outlet.
6. Connect the USB cable from the USB-2416-4AO to the host computer USB port.

USB-2416-4AO User's Guide Installing the USB-2416-4AO
9
Connect to a USB 2.0 high speed hub to achieve the highest transfer rate (480 Mbps). When connected to a
USB 1.1 full-speed port, the transfer rate is limited to 12 Mbps.
Configuring the hardware
Except for the DIO pull-up selection, all hardware configuration options on the USB-2416-4AO are software
controlled. You can select some of the configuration options using InstaCal, such as the analog input
configuration (single-ended or differential channels). When measuring from thermocouples, make sure you
configure the channels for differential mode.
Caution! Turn off power to all devices connected to the system before making connections. Electrical shock
or damage to equipment can result even under low-voltage conditions.
Information on signal connections
General information regarding signal connection and configuration is available in the Guide to Signal
Connections. This document is available on our web site at www.mccdaq.com/signals/signals.pdf.
Caution! Always handle components carefully, and never touch connector terminals or circuit components
unless you are following ESD guidelines in an appropriate ESD-controlled area. These guidelines
include using properly-grounded mats and wrist straps, ESD bags and cartons, and related
procedures.
Avoid touching board surfaces and onboard components. Only handle boards by their edges. Make
sure the USB-2416-4AO does not come into contact with foreign elements such as oils, water, and
industrial particulate.
The discharge of static electricity can damage some electronic components. Semiconductor
devices are especially susceptible to ESD damage.
Connecting the board for I/O operations
Connectors, cables – main I/O connector
The following table lists the board connectors and compatible accessory products for the USB-2416-4AO.
Main connector specifications
Main connectors Six banks of detachable screw terminals
Compatible accessory product for the 37-pin expansion
connector AI-EXP32 expansion board with screw terminals (connects directly to the USB-2416-4AO)

USB-2416-4AO User's Guide Installing the USB-2416-4AO
10
Screw terminal pin out – differential
Figure 4. 16-channel differential mode pin out
Differential connection guidelines
 When connecting differential voltage inputs to a "floating" voltage source, make sure there is a DC return
path from each voltage input to ground. You make this path by connecting a resistor from each input to a
GND pin (pins 18, 36, 39, 42, 44, 46, 66, 81, 84). A value of approximately 100 kΩ can be used for most
applications.
Leave unused input channels either floating or tied to GND (pins 18, 36, 39, 42, 44, 46, 66, 81, 84).
Source impedances should be kept as small as possible to avoid settling time and accuracy errors.
 When configuring thermocouple sensors, keep any stray capacitance as small as possible relative to GND
(pins 18, 36, 39, 42, 44, 46, 66, 81, 84) to avoid settling time and accuracy errors. For thermocouple
channels, do not provide a return path to ground. This is done internally.

USB-2416-4AO User's Guide Installing the USB-2416-4AO
11
Screw terminal pin out – single-ended
Figure 5. 32-channel single-ended mode pin out
Figure 6. DSUB37 expansion connector pinout
The AI-EXP32 expansion port is intended to interface directly with the USB-2416-4AO. Do not attempt to use
any of the expansion port pins for any other purpose.
Power-down the USB-2416-4AO before you connect it the AI-EXP32 expansion board.

12
Chapter 3
Functional Details
This chapter contains detailed information on all of the features available from the board, including:
 explanations of the physical device components
 a functional block diagram and mechanical drawings
 information on how to use the signals generated by the device
 diagrams of signals using default or conventional device settings
USB-2416-4AO components
These USB-2416-4AO components are shown in Figure 7 and Figure 8.
 One USB connector
 One external power connector
 Two LED indicators Power and Activity)
 One 37-pin DSUB expansion connector
 Six removable screw terminal blocks
Figure 7. USB-2416-4AO components – front view
Figure 8. USB-2416-4AO components – rear view

USB-2416-4AO User's Guide Functional Details
13
LEDs
When the USB-2416-4AO is connected to a computer, in its normal idle state both LEDs are lit solid green.
Power LED
The Power LED is the top LED on the right side of the USB-2416-4AO housing.
The Power LED blinks when you plug the power supply into the USB-2416-4AO, and continues to blink while
the device initializes the hardware. If it continues blinking for more than ½ second, then there is a problem with
the USB-2416-4AO and you should cycle the power.
If an application issues a "blink LED" command, then the power LED blinks a few times.
Activity LED
The (USB) Activity LED is the bottom LED on the right side of the USB-2416-4AO housing. It blinks rapidly
when both the USB cable and external power cables are plugged in. It continues blinking rapidly while the
device is connecting to the computer, and then turns solid.
Whenever the device receives a USB command, the Activity LED blinks off and then returns to solid green.
When an analog in scan is running, the Activity LED blinks continuously.
USB connector
The USB connector is on the right side of the USB-2416-4AO provides communication.
External power connector
The USB-2416-4AO require external power through this connector to provide sufficient power for the USB-
2416-4AO.
Connect the PS-5V2AEPS power supply to the external power supply connector. This power supply provides
5 VDC, 2 A power to the USB-2416-4AO.
Screw terminal wiring
The USB-2416-4AO has six groups of screw terminals—three on each side of the housing. Each group has
16 connections. Pin numbers are identified in Figure 4 and Figure 5.
Analog/TC input terminals
You can connect up to 32 single-ended analog input connections or up to 16 differential analog/TC input
connections to these screw terminal pins.

CH0H and CH0L
 CH1H and CH1L
 CH2H and CH2L
 CH3H and CH3L
 CH4H and CH4L
 CH5H and CH5L
 CH6H and CH6L

CH7H and CH7L

CH8H and CH8L
 CH9H and CH9L
 CH10H and CH10L
 CH11H and CH11L
 CH12H and CH12L
 CH13H and CH13L
 CH14H and CH14L

CH15H and CH15L
You can select a unique input range or signal type for each channel. For example, one channel could be used for
volts and another for temperature.
When connecting differential voltage inputs to a "floating" voltage source, make sure there is a DC return path
from each voltage input to ground. You make this path by connecting a resistor from each input to a GND pin
(pins 18, 36, 39, 42, 44, 46, 66, 81, 84). A value of approximately 100 kΩ can be used for most applications.
This does not apply to channels configured for thermocouple input, as they have their own internal reference.

USB-2416-4AO User's Guide Functional Details
14
Leave unused input channels either floating or tied to GND (pins 18, 36, 39, 42, 44, 46, 66, 81, 84).
Source impedances should be kept as small as possible to avoid settling time and accuracy errors.
Analog input mode
The USB-2416-4AO makes high-resolution voltage measurements in either a single-ended or fully differential
mode. You can configure the USB-2416-4AO for the following voltage input ranges.
 ±20 V
 ±10 V
 ±5 V
 ±2.5 V
 ±1.25 V
 ±0.625 V
 ±0.3125 V
 ±0.15625 V
 ±0.078125 V
Each analog input channel has the following measurement parameters:
 signal type of volts or thermocouple type J, K, T, E, R, S, B, or N
 full scale voltage from -20 to + 20 VDC
Thermocouple inputs
You can make up to 16 high-resolution differential thermocouple measurements with the USB-2416-4AO.
Built-in cold-junction sensors are provided for each of the screw-terminal blocks, and any supported TC type
can be attached to any of the 16 thermocouple channels.
Do not connect thermocouples as single-ended—doing so can cause false readings.
You do not need to use ground-referencing resistors because the analog front-end circuit level-shifts the
thermocouple's output into the common-mode input range of the A/D.
When configuring thermocouple sensors, keep any stray capacitance as small as possible relative to GND
(pins 18, 36, 39, 42, 44, 46, 66, 81, 84) to avoid settling time and accuracy errors.
The USB-2416-4AO also provides an open thermocouple detection (OTD) feature for each of the analog input
channels configured for thermocouple measurement. This feature is automatically enabled as part of the overall
acquisition process, and detects if an open-circuit condition exists at the thermocouple sensor.
The USB-2416-4AO provides electrostatic discharge (ESD) protection for each of the thermocouple inputs.
However, before handling thermocouple sensors, follow standard ESD practices and discharge any accumulated
ESD charge.
The USB-2416-4AO includes an ESD protection device at each of the analog input terminal block pins. If an
ESD or transient voltage is coupled into the device, the input protection device(s) clamps the voltage to protect
the thermocouple input circuitry from possible damage.
Once the thermocouple sensor is connected to the USB-2416-4AO, the configuration options have been
selected, and the recommended 45 minute warm up has elapsed, the USB-2416-4AO is ready to make high-
resolution differential voltage measurements.
Cold junction compensation (CJC) is needed to compensate for the additional thermal EMF's generated by
connecting the thermocouple leads to the USB-2416-4AO terminal blocks.
CJC is performed using a high-resolution temperature sensor connected close to the USB-2416-4AO's terminal
blocks. The USB-2416-4AO includes four separate CJC sensors—two on each side of the PCB. Software
corrects for the additional thermocouples created at the terminal.
Once the A/D and CJC data is collected, the application software uses this data to linearize to an accurate
temperature reading. The thermocouple linearization uses the latest NIST linearization coefficients for each of
the eight thermocouple types supported by the USB-2416-4AO.

USB-2416-4AO User's Guide Functional Details
15
Figure 9 below shows a typical thermocouple connection.
Figure 9. Differential thermocouple connection example
Noise filtering, data rate, and throughput rate
Although the USB-2416-4AO A/D converter has a maximum data rate of 3,750 S/s, the actual throughput rate
you observe for voltage and temperature data is determined by these formulas.
 Maximum single-channel throughput:
s
ratedata
µ 640
11
+
 Maximum multiple-channel throughput:
∑






+
nμs640
ratedata
1
1
where nis the number of channels
See Table 18 and Table 19 in the Specifications chapter for details.
This drop-off in throughput rate is due to the USB-2416-4AO's noise filtering feature. You can control the
amount of the noise filtering by adjusting the data rate setting. By reducing the data rate, the averaging of
samples increases, and noise drops correspondingly.

USB-2416-4AO User's Guide Functional Details
16
Figure 10 below illustrates this inverse relationship. This graph applies to the A/D converter only—do not
expect this level of performance from the USB-2416 itself.
Figure 10. USB-2416-4AO A/D converter data rate vs. noise graph
If low noise is your main concern, you can operate the USB-2416-4AO at very low data rates starting from 2.5
S/s. At low rates, much of the noise is averaged out of the data, and issues such as reference noise become less
important.
At higher data rates, higher-frequency noise sources are not averaged out and begin to be troublesome. These
noise sources include the noise inherent in the A/D converter itself, which is not reducible.
Since thermocouples can pick up noise in your environment, select a data rate based on the primary noise
frequency. For example, to reduce the effect of 60 Hz noise, select a data rate of 60 (or a sub-multiple of 60,
such as 10 or 20).
Multiple-channel throughput rates
When setting different sample rates for different channels, be aware that the all channels will be sampled within
the same sample window based on the channel with the lowest sample rate.
For example, if you set a 10 Hz data rate for channel 0, and a 50 Hz data rate for channel 1, basically, both
channels pass the same number of samples per second to the host computer. However, more averaging is
performed on channel 0's samples; therefore, channel 0 is sampled at a higher resolution.
The USB-2416-4AO's A/D converter performs averaging, and the number of averages equals 30,000/data rate.
In this example, channel 0 is sampled 3000 times over 100 ms, and all samples are averaged into one sample.
Then, channel 1 is sampled 600 times over 20 ms, and samples are likewise averaged into one sample.
The final samples are available to you at a maximum rate of about 8 Hz (8.245 Hz).
Figure 11. USB-2416-4AO data rate vs. resolution example
Input isolation
The USB-2416-4AO is an isolated data acquisition device. The analog input, digital I/O, counters, and all the
digital control/timing are referenced to an isolated ground as shown in the figure below. This ground is
physically and electrically separate from the ground use by the circuit connected to the system bus interface.
Isolation provides a barrier between the host computer and potentially hazardous voltages by physically and
electrically separating two parts of the measurement device.

USB-2416-4AO User's Guide Functional Details
17
 The non-isolated ground is common to the chassis ground of the computer, while the isolated ground is not.
 All analog measurements are made relative to the isolated ground. See Figure 12 for details.

Figure 12. USB-2416-4AO input isolation diagram
When making measurements in industrial environments, DAQ devices can encounter hazardous voltages,
transients, large common mode voltages and fluctuating ground potentials. Any one of these issues can
seriously degrade the measurement accuracy of the device and possibly damage the measurement instrument.
To overcome these issues, some DAQ devices provide physical and electrical isolation. Some of the benefits of
isolation include:
 Safety: A DAQ device employing physical and electrical isolation helps to keep high voltages and
transients from damaging the system-side host PC.
 Ground loops: Improper grounding of the signal source that the DAQ device is measuring is one of the
most common sources of noise and measurement inaccuracies. Isolation improves the measurement
accuracy by physically preventing ground loops. Ground loops—a common source of noise and error—are
the results of a measurement system having multiple grounds at different potentials.
 Common mode rejection: With isolation, a DAQ device can measure small signals in the presence of large
common mode voltages. Isolation increases the measurement system's ability to reject common mode
voltages. The common mode voltage is the signal that is common to both the positive and negative inputs
of the measurement device, but is not part of the signal to measure.
Analog output terminals (VDAC0 through VDAC3)
The USB-2416-4AO has four 16-bit analog output channels with a ±10 V output range.
Analog outputs can be updated at a maximum rate of 1 kS/s.
Digital I/O
The USB-2416-4AO provides up to eight digital I/O lines with read/write rates of 500 port reads or single bit
reads per second.
Digital input voltage ranges of 0 V to 15 V are permitted, with thresholds of 0.6 V (low) and 2.6 V (high). Each
DIO channel is an open-drain, which, when used as an output, is capable of sinking up to 150 mA for direct
drive applications. The maximum sink current is 150 mA per eight-channel bank, or if all eight channels are
used, 18 mA (maximum) per channel.
Figure 13 is an example of a typical DIO connection. The figure represents connections for one channel. The
other seven channels are connected in the same manner.

USB-2416-4AO User's Guide Functional Details
18
Figure 13. Digital output connection example
Internal pull-up/pull-down capability
Each of the eight DIO bits on the USB-2416-4AO has a 47 kΩ pull-up/pull-down resistor. To configure these
bits for the 0 V pull-down option, you must open the USB-2416-4AO case to access the three-pin jumper
labeled JP1.
To open the case and set the JP1 jumper, do the following.
1. Turn over the USB-2416-4AO and rest it on its top on a flat, stable surface.
2. Remove the five screws shown in Figure 14 from the bottom of the module.
3. Holding both the top and bottom sections of the module, turn it over, rest it on the surface, and carefully
remove the top portion of the case.
Figure 14. Location of screws connecting bottom and top sections of case

USB-2416-4AO User's Guide Functional Details
19
Figure 15. Location of JP1
The pull-up/pull-down voltage is common to all of the internal 47 kΩ resistors.
External pull-up/pull-down capability
You can also place an external pull-up resistor on any of the DIO bits. This enables you to pull the DIO bit up to
a voltage that exceeds the internal +5 V pull-up voltage.
When using external pull-up resistors, note the following:
 You should either remove the JP1 jumper or store it by attaching it to one of the three pins.
 When using external pull-up resistors, the internal resistors cause slight impedance shifts to digital lines in
the "on" state as the number of lines in the "off" state changes.
Figure 16. Digital I/O external resistor configuration
Counter input terminals (CTR0, CTR1)
Two 32-bit event counters are built into the USB-2416-4AO. Each counter accepts frequency inputs up to
1 MHz.
Refer to the Screw terminal pinout diagrams starting on page 10 for the location of these pins. The internal
counter increments when the TTL levels transition from low to high. The counter can count frequencies of up to
1 MHz.

USB-2416-4AO User's Guide Functional Details
20
USB-2416-4AO mechanical drawings
Figure 17. Circuit board (top) and enclosure dimensions