Measurement Computing USB-1808X User manual

USB-1808X
Eight-Channel Simultaneous-Sampling Multifunction Device
User's Guide
May 2019. Rev 4
© Measurement Computing Corporation

2
HM USB-1808X.docx
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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-1808X..................................................................................................................6
Functional block diagram ...................................................................................................................................6
Chapter 2
Installing the USB-1808X......................................................................................................................7
Unpacking...........................................................................................................................................................7
Installing the software ........................................................................................................................................7
Installing the hardware .......................................................................................................................................7
Calibrating the hardware.....................................................................................................................................7
Updating firmware..............................................................................................................................................7
Chapter 3
Functional Details .................................................................................................................................8
External components ..........................................................................................................................................8
USB connector.................................................................................................................................................................. 8
Screw terminals................................................................................................................................................................. 8
LEDs ................................................................................................................................................................................10
Analog input .....................................................................................................................................................10
Channel-Gain queue ........................................................................................................................................................10
Analog output ...................................................................................................................................................11
Digital I/O.........................................................................................................................................................11
Digital input scanning......................................................................................................................................................11
Pull-up/down configuration .............................................................................................................................................11
Counter input ....................................................................................................................................................12
Totalize counter mode......................................................................................................................................................13
Period measurement mode...............................................................................................................................................13
Pulse width measurement mode.......................................................................................................................................13
Quadrature encoder input .................................................................................................................................13
Timer output .....................................................................................................................................................14
Synchronous I/O – mixing analog, digital, and counter scanning ....................................................................15
Clock I/O ..........................................................................................................................................................15
Digital triggering ..............................................................................................................................................15
Pattern triggering ..............................................................................................................................................15
Mask option .....................................................................................................................................................................15
Ground..............................................................................................................................................................16
Power output.....................................................................................................................................................16
Mechanical drawings........................................................................................................................................17
Chapter 4
Specifications......................................................................................................................................18
Analog input .....................................................................................................................................................18
Accuracy...........................................................................................................................................................19
Analog input DC voltage measurement accuracy ............................................................................................................19
Dynamic performance......................................................................................................................................................19

USB-1808X User's Guide
4
Noise performance ...........................................................................................................................................................19
Analog output ...................................................................................................................................................20
Analog input/output calibration........................................................................................................................21
Digital input/output...........................................................................................................................................21
Counter .............................................................................................................................................................22
Quadrature inputs.............................................................................................................................................................22
Timer ................................................................................................................................................................23
External clock input/output...............................................................................................................................23
External trigger .................................................................................................................................................24
Pattern trigger ...................................................................................................................................................24
Memory ............................................................................................................................................................24
Power ................................................................................................................................................................24
USB ..................................................................................................................................................................25
Environmental ..................................................................................................................................................25
Mechanical .......................................................................................................................................................25
Screw terminal connector .................................................................................................................................25
Differential mode pinout..................................................................................................................................................26
Single-ended mode pinout ...............................................................................................................................................27
EU Declaration of Conformity............................................................................................................28

5
Preface
About this User's Guide
What you will learn from this user's guide
This user's guide describes the Measurement Computing USB-1808X data acquisition device and lists device
specifications.
Conventions in this user's guide
For more information
Text presented in a box signifies additional information and helpful hints related to the subject matter 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 is used for the names of objects on a screen, such as buttons, text boxes, and checkboxes.
Italic text is used for the names of manuals and help topic titles, and to emphasize a word or phrase.
Where to find more information
Additional information about USB-1808X hardware is available on our website at www.mccdaq.com. You can
also contact Measurement Computing Corporation with specific questions.
Knowledgebase: kb.mccdaq.com
Tech support form: www.mccdaq.com/support/support_form.aspx
Email: [e-mail]
Phone: [phone] and follow the instructions for reaching Tech Support
For international customers, contact your local distributor. Refer to the International Distributors section on our
web site at www.mccdaq.com/International.

6
Chapter 1
Introducing the USB-1808X
The USB-1808X is a multifunction data acquisition device providing the following features:
Eight 18-bit simultaneous-sampling differential (DIFF) or single-ended (SE) analog input channels –
software-selectable per channel as DIFF or SE
Sample rate of 200 kS/s per channel maximum
Analog input ranges of ±10 V, ±5 V, 0 V to 10 V, and 0 V to 5 V – software-selectable per channel
Two 16-bit analog outputs
Four individually-configurable digital I/O channels
Two high-speed general-purpose counters
Two quadrature encoder inputs
Two timer outputs
One external digital trigger for data acquisition and one external digital trigger for data generation
Two external clock inputs and two clock outputs for synchronous input and output operations with more
than one device.
Screw terminals for field wiring connections
The device is powered by the +5 V USB supply from the computer, requiring no external power.
The USB-1808X is a USB 2.0 high-speed device that is fully compatible with both USB 1.1, USB 2.0, and
USB 3.0 ports.
Functional block diagram
USB-1808X functions are illustrated in the block diagram shown here.
Figure 1. Functional block diagram

7
Chapter 2
Installing the USB-1808X
Unpacking
As with any electronic device, you should take care while handling to avoid damage from static
electricity. Before removing the device from its packaging, ground yourself using a wrist strap or by simply
touching the computer chassis or other grounded object to eliminate any stored static charge.
Contact us immediately if any components are missing or damaged.
Installing the software
Refer to the MCC DAQ Quick Start and the USB-1808X product page on our website for information about the
software supported by the USB-1808X.
Install the software before you install your device
The driver needed to run the USB-1808X is installed with the software. Therefore, you need to install the
software package you plan to use before you install the hardware.
Installing the hardware
To connect the USB-1808X to your system, connect the USB cable to an available USB port on the computer or
to an external USB hub connected to the computer. Connect the other end of the USB cable to the USB
connector on the device. No external power is required.
When connected for the first time, a Found New Hardware dialog opens when the operating system detects the
device. When the dialog closes, the installation is complete. The Status LED on the USB-1808X turns on after
the device is successfully installed.
If the Status LED turns off
If communication is lost between the device and the computer, the device LED turns off. To restore
communication, disconnect the USB cable from the computer and then reconnect it. This should restore
communication, and the LED should turn on.
Calibrating the hardware
The Measurement Computing Manufacturing Test department performs the initial factory calibration. Return
the device to Measurement Computing Corporation when calibration is required. The recommended calibration
interval is one year.
Updating firmware
Your DAQ device contains firmware that can be updated in the field if required. Firmware is available for
download at www.mccdaq.com/firmware.aspx. MCC recommends that you check this page periodically to see
if an update to your device firmware is available.

8
Chapter 3
Functional Details
External components
The USB-1808X has the following external components (see Figure 2 through Figure 4 on pgs. 9-10):
USB connector
LEDs
Screw terminals
USB connector
The USB connector provides +5 V power and communication. No external power supply is required.
Screw terminals
The screw terminals provide the following connections:
Eight DIFF analog inputs (CH0H/CH0L to CH7H/CH7L) or eight SE analog inputs (CH0Hto CH7H)
Refer to Figure 2 and Figure 3 on page 9 for DIFF and SE pinouts.
Two analog outputs (AOUT0and AOUT1)
Four digital I/O lines (DIO0 to DIO3)
Two general-purpose counter inputs (CTR0and CTR1)
Two quadrature encoder inputs (ENC0A, ENC0B, ENC0Z and ENC1A, ENC1B, ENC1Z)
Two timer outputs (TMR0 and TMR1)
An external trigger input (ITRIG)and an external trigger output OTRIG)
Two external clock inputs (ICLKI and OCLKI) and two external clock outputs (ICLKO, OCLKO)
One +5 V power output (+VO) connection
Ten analog ground (AGND) and seven digital ground (GND) connections
Use 16 AWG to 30 AWG wire when making connections to the screw terminals.

USB-1808X User's Guide Functional Details
9
Figure 2. DIFF mode pinout
Figure 3. SE mode pinout

USB-1808X User's Guide Functional Details
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LEDs
The USB-1808X has two LED indicators that indicate the status of power and data. The LEDs are stacked one
above the other, as shown in Figure 4.
The Status LED turns on when the device is detected by the computer.
The Activity LED blinks when data is transferred and is off otherwise.
1
USB connector
3
Activity LED
2
Status LED
Figure 4. LED indicators
Analog input
You can configure each analog input channel for either SE or DIFF mode. MCC recommends connecting
unused analog input terminals to analog ground terminals during operation. For example, if you are not using
CH7L, connect this terminal to an available AGND terminal.
The input voltage range is software-selectable per channel for ±10 V, ±5 V, 0 V to 10 V, or 0 V to 5 V.
Analog input operations can be paced by the internal clock or by an external clock (ICLKI – refer to Clock I/O
on page 15). They can be initiated by a digital trigger (Digital triggering on page 15) or a pattern trigger
(Pattern triggering on page 15).
Refer to Synchronous I/O – mixing analog, digital, and counter scanning on page 15 for information on running
analog input scans at the same time as other subsystem scans.
For more information about analog signal connections
For more information about analog input connections, refer to the Guide to DAQ Signal Connections (available
for download at www.mccdaq.com/support/DAQ-Signal-Connections.aspx).
Channel-Gain queue
The channel-gain queue feature allows you to configure a different gain setting for each channel. The gain
settings are stored in a channel-gain queue list that is written to local memory on the device.
The channel-gain queue list can contain up to eight unique elements. The channel list must be in increasing
order. An example of a five-element list is shown in the following table.
Sample channel-gain queue list
Element Channel Range
0
CH0H/CH0L (DIFF)
±10 V
1
CH2H/AGND (SE)
±5 V
2
CH3H/AGND (SE)
0 V to 5 V
3
CH6H/CH6L (DIFF)
0 V to 10 V
4
CH7H/CH7L (DIFF)
±5 V

USB-1808X User's Guide Functional Details
11
Carefully match the gain to the expected voltage range on the associated channel or an over range condition
may occur. Although this condition does not damage the device, it does produce a useless full-scale reading,
and can introduce a long recovery time due to saturation of the input channel.
Analog output
The two 16-bit analog outputs (AOUT0 and AOUT1) can be updated simultaneously at a rate of 500 kS/s per
channel. Each output can be updated at a rate of 500 kS/s. The output range is fixed at ±10 V. The outputs
default to 0 V at power up, or when a reset command is issued to the device.
Analog output operations can be paced by the internal clock or by an external clock (OCLKI – refer to Clock I/O
on page 15). They can be initiated by a digital trigger (Digital triggering on page 15) or a pattern trigger
(Pattern triggering on page 15).
Refer to Synchronous I/O – mixing analog, digital, and counter scanning on page 15 for information on running
analog output scans at the same time as other subsystem scans.
Digital I/O
You can connect up to four digital I/O lines to DIO0 through DIO3. Each digital channel is individually
configurable for input or output. During initial power on or reset, the digital pins are set for input.
The digital I/O terminals can detect the state of any TTL-level input. Refer to the schematic shown in Figure 5.
Figure 5. Schematic showing switch detection by digital channel DIO0
If you set the switch to the +5 V input, DIO0 reads TRUE (1). When set to GND, DIO0 reads FALSE (0).
Digital input scanning
Digital input operations can be paced by the internal clock or by an external clock (ICLKI – refer to Clock I/O
on page 15). They can be initiated by a digital trigger (Digital triggering on page 15) or a pattern trigger
(Pattern triggering on page 15).
If no analog inputs are being scanned, the digital inputs can sustain rates up to 200 kHz. Digital input ports can
also be read asynchronously before, during, or after an analog input scan.
Refer to Synchronous I/O – mixing analog, digital, and counter scanning on page 15 for information on running
digital input scans at the same time as other subsystem scans.
Pull-up/down configuration
All digital I/O lines are pulled down to 0 V (LO) with a 47 kΩ resistor (default). You can change the
pull-up/down configuration using the internal jumper labeled DIO. You must remove the device housing to
access the jumper on the circuit board.
To set the jumper for pull-up or pull-down, complete the following steps.
1. Unplug the device from the computer.
2. Turn the device over and rest the top of the housing on a flat, stable surface.
Caution! The discharge of static electricity can damage some electronic components. Before removing the
USB-1808X from its housing, ground yourself using a wrist strap or touch the computer chassis or
other grounded object to eliminate any stored static charge.
3. Remove the rubber fee from the bottom of the device, and the four screws using a #1 Philips head
screwdriver.

USB-1808X User's Guide Functional Details
12
4. Hold both the top and bottom sections together, turn the device over and rest it on the surface, then
carefully remove the top section of the case to expose the circuit board.
Figure 6 shows the location of the DIO jumper on the circuit board.
Figure 6. Pull-up/down jumper location
5. Configure the DIO jumper for pull-up or pull-down, as shown in Figure 7.
Figure 7. Pull-up/down jumper configuration
6. Replace the top section of the housing and fasten it to the bottom section with the four screws.
For more information about digital signal connections
For general information about digital signal connections and digital I/O techniques, refer to the Guide to DAQ
Signal Connections (available for download at www.mccdaq.com/support/DAQ-Signal-Connections.aspx).
Counter input
Counter inputs can be read asynchronously under program control, or synchronously as part of a digital scan
group.
The CTR0and CTR1 terminals are 32-bit general-purpose counters that can accept frequency inputs up to
50 MHz.
The USB-1808X supports the following counter input modes:
Totalize
Period measurement
Pulse-width measurement
Counter input modes are programmable with software. Each mode supports additional counter operation
options.

USB-1808X User's Guide Functional Details
13
Typically, when data is acquired with no counter operation options set, the count of each counter channel is set
to 0 and latched at the beginning of the acquisition.
When counter options are set the counters can concurrently monitor time periods, frequencies, pulses, and other
event-driven incremental occurrences directly from pulse-generators, limit switches, proximity switches, and
magnetic pick-ups.
Counter input operations can be paced by the internal clock or by an external clock (ICLKI – refer to Clock I/O
on page 15). They can be initiated by a digital trigger (Digital triggering on page 15) or a pattern trigger
(Pattern triggering on page 15).
Refer to Synchronous I/O – mixing analog, digital, and counter scanning on page 15 for information on running
counter input scans at the same time as other subsystem scans.
Totalize counter mode
The USB-1808X can be used as a high-speed pulse counter for general counting applications. The internal
counter increments when the TTL levels transition from low to high or from high to low.
Each option supported in Totalize mode is explained in following table:
Totalize counter mode options
Counter option Description
Clear on read
The counter is cleared after each read (synchronous or asynchronous). The value of the counter
before it was cleared is latched and returned.
Range limit
When counting up: The counter rolls over to MINLIMIT (or stops if Non-recycle is set) when the
maximum count (specified by the MAXLIMIT value) is reached.
When counting down: The counter counts down to MINLIMIT and then rolls over to MAXLIMIT
(or stops if Non-recycle is set).
Non-recycle
The counter stops if a count overflow or underflow occurs (or, if Range limit is set, the MAXLIMIT
or MINLIMIT value is reached). Counting resumes if direction is reversed or the counter is reloaded.
Period measurement mode
Use period mode to measure the period of a signal at a counter channel's input. You can measure x1, x10, x100
or x1000 periods for 32-bit values. Four resolutions are available — 20 ns, 200 ns, 2000 ns, or 20,000 ns. All
period measurement mode options are software-selectable. The 100 MHz system clock is used as the timing
source. Periods from sub-microsecond to many seconds can be measured.
Pulse width measurement mode
Use pulse width mode to measure the time from the rising edge to the falling edge, or vice versa, on a counter
input signal. Four resolutions are available — 20 ns, 200 ns, 2000 ns, or 20,000 ns. All pulse width
measurement mode options are software selectable. The 100 MHz system clock is used as the timing source.
Pulse widths from sub-microsecond to many seconds can be measured.
Quadrature encoder input
The USB-1808X can simultaneously decode signals from up to two encoders. Quadrature encoders, 50 MHz
maximum pulse frequency, and X1, X2, and X4 count modes are supported.
The USB-1808X provides A, B, and Z inputs – ENCxA, ENCxB, and ENCxZ – for each connected encoder.
A typical encoder generates the A and B signals at a 90° phase shift with respect to each other. These signals are
used to determine system position (counts), velocity (counts per second), and direction of travel or rotation. The
Z signal can be programmed to latch the current count or reload the counter with the MINLIMIT value
(counting up) or the MAXLIMIT value (counting down).
The Z signal may be used to establish an absolute reference position within one count of the encoder travel or
rotation. This signal can be used to reload the position counter, which is useful at system startup when the
incremental encoder cannot determine the starting position.

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Encoder input operations can be paced by the internal clock or by an external clock (ICLKI – refer to Clock I/O
on page 15). They can be initiated by a digital trigger (Digital triggering on page 15) or a pattern trigger
(Pattern triggering on page 15).
Refer to Synchronous I/O – mixing analog, digital, and counter scanning on page 15 for information on running
quadrature encoder scans at the same time as other subsystem scans.
Each supported quadrature encoder option is explained in following table:
Quadrature encoder options
Encoder
option
Description
Count mode
Select X1, X2, or X4. Count modes provide different levels of accuracy with respect to the encoder
position.
X1: counts rising edges on input A.
X2: counts rising edges and falling edges on input A.

X4: count rising and falling edges on both inputs A and B.
Range limit
When counting up: The counter stops when the maximum count (specified by the MAXLIMIT
value) is reached. Counting resumes if direction is reversed or the counter is cleared.
When counting down: The counter stops when the minimum count (specified by the MINLIMIT
value) is reached. Counting resumes if direction is reversed or the counter is cleared.
Quadrature encoder options that are specific to the Z signal (ENCxZ) are is explained in following table.
Z input quadrature encoder options ()
Counter mode Description
Clear on Z
The counter is cleared by the Z signal.
Latching
Latching mode allows the count to be latched by the Z signal.
Timer output
You can use TMR0 through TMR1 as 32-bit timer outputs. Each timer can generate pulse rates of up to 50 MHz,
with programmable pulse widths down to 10 ns.
The timer output rate and pulse width can be updated asynchronously at any time, however, doing so results in a
pulse stream that is not seamless.
The following timer output options are software-selectable:
pulse frequency
duty cycle (pulse width divided by the pulse period)
number of pulses to generate
time delay before starting the timer output after it is enabled
idle state of the output (idle high or idle low)
The time delay can range from 0 seconds to 42.94 seconds.
Figure 8. USB-1808X PWM timer channel
Timer output operations can be paced by the internal clock or by an external clock (OCLKI – refer to Clock I/O
on page 15). They can be initiated by a digital trigger (Digital triggering on page 15).

USB-1808X User's Guide Functional Details
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Synchronous I/O – mixing analog, digital, and counter scanning
The USB-1808X can read analog, digital, and counter inputs, and generate up to two analog outputs and one
digital pattern output at the same time. Digital and counter inputs do not affect the overall A/D rate because
these inputs use no time slot in the scanning sequencer.
For example, one analog input channel can be scanned at the full 200 kS/s A/D rate along with digital and
counter input channels. Each analog channel can have a different gain, and counter and digital channels do not
need additional scanning bandwidth if there is at least one analog channel in the scan group. Digital input
channel sampling is done during the dead time of the scan period when no analog sampling is being done.
Clock I/O
The USB-1808X provides one external clock input (ICLKI) and one clock output (ICLKO) for input operations.
Connect an external clock signal to ICLKI.
The pacer clock is available at ICLKO.
The USB-1808X provides one external clock input (OCLKI) and one clock output (OCLKO) for output
operations.
Connect an external clock signal to OCLKI.
The pacer clock is available at OCLKO.
Digital triggering
The ITRIG (for triggering input operations) and OTRIG (for triggering output operations) terminals are external
digital trigger inputs. The trigger mode is software-selectable for edge or level sensitive. Edge sensitive mode is
selectable for rising or falling. Level sensitive mode is selectable for high or low.
Pattern triggering
You can also start an input or output scan with a digital pattern trigger using DIO0 – DIO3. The pattern
represents the state of up to four bits on the port.
You specify the pattern and the trigger type with software. Supported trigger types are Above Pattern, Below
Pattern, Equal Pattern, and Not Equal Pattern. The scan begins when the trigger conditions are met.
The base clock is fixed at 100 MHz (10 ns). The trigger pattern must be held for five base clock cycles (50 ns)
to ensure that it is properly detected. The trigger latency is 1 scan clock period + 8 base clock cycles (80 ns).
Mask option
Use a bitmask to specify which bits to include or exclude from the pattern to detect. To include a bit in the
pattern, sets its value to 1. To exclude a bit from the pattern, sets its value to 0. Refer to the pattern and mask
values shown in Figure 9 and Figure 10.
In Figure 9 all mask bits are set to 1, so all the bits are included in the pattern to detect.
Figure 9. Trigger mask with all bits included

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In Figure 10 all mask bits are excluded except bit 3. The result of this operation is that only bit 3 is included in
the pattern to detect.
Figure 10. Trigger mask with some bits excluded
Ground
The analog ground (AGND) terminals provide a common ground for all analog channels.
The digital ground (GND) terminals provide a common ground for the digital, trigger, counter, and encoder
terminals.
Power output
The +VO terminal can output up to 10 mA maximum. You can use this terminal to supply power to external
devices or circuitry.

USB-1808X User's Guide Functional Details
17
Mechanical drawings
Figure 11. USB-1808X circuit board (top) and enclosure dimensions

18
Chapter 4
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. General analog input specifications
Parameter Condition Specification
A/D converter type
Simultaneous
ADC resolution
18 bits
Number of channels
8 differential (DIFF), 8 single-ended (SE);
software-selectable per-channel for SE or DIFF
Input voltage range
±10 V, ±5 V, 0 V to 10 V, 0 V to 5 V
Software-selectable per channel
Absolute max input voltage
CHx relative to AGND

±25 V max (power on)

±15 V max (power off)
Input impedance

>1 GΩ (power on)

1000 Ω (power off)
Input bias current
±50 pA
Input bandwidth All input ranges, small signal
(–3 dB)
2.0 MHz
Input capacitance
50 pf
Common mode voltage
range
±10 V range ±10.1 V
±5 V range
±10.1 V
0 V to 10 V range
±10.1 V
0 V to 5 V range
±10.1 V
Common mode rejection
ratio
f
IN
≤1 kHz, all input ranges
90 dB
Crosstalk
±10 V, adjacent channels,
DC to 100 kHz
–95 dB
Input coupling
DC
Sample rate
0.023 Hz to 200 kHz; software-selectable
Scan clock source
Internal input scan clock or external input scan
clock (ICLKI pin)
Trigger source

ITRIG (see External trigger on page 24)
Digital pattern detection (see Pattern trigger on
page 24)
Channel gain queue Up to 8 elements Software-selectable. Queue list may contain up to
eight elements of unique, consecutive channels
paired with any valid range.
Warm-up time
15 minutes min

USB-1808X User's Guide Specifications
19
Accuracy
Analog input DC voltage measurement accuracy
Table 2. DC accuracy components and specifications. All values are (±)
Range
Gain error
(% of
reading)
Offset
error
(mV)
INL error
(% of
range)
Absolute
accuracy at
Full Scale
(mV)
Gain
temperature
coefficient
(% reading/°C)
Offset
temperature
coefficient
(µV/°C)
±10 V
0.020
1.5
0.00076
3.576
0.00023
4
±5 V
0.020
1.0
0.00057
2.028
0.00023
4
0 V to 10 V
0.020
1.5
0.00028
3.528
0.00023
4
0 V to 5 V
0.020
1.0
0.00014
2.007
0.00023
4
Dynamic performance
Table 3. Dynamic performance specifications
Range Condition Specification
±10 V
Signal-to-noise ratio (SNR)
94 dB
Signal-to-noise-and-distortion ratio
(SINAD)
94 dB
Total harmonic distortion (THD)
–108 dB
Spurious free dynamic range (SFDR)
112 dB
Effective number of bits (ENOB)
15.3 bits
±5 V
SNR
91 dB
SINAD
91 dB
THD
–105 dB
SFDR
107 dB
ENOB
14.8 bits
0 V to 10 V
SNR
87 dB
SINAD
87 dB
THD
–104 dB
SFDR
109 dB
ENOB
14.5 bits
0 V to 5 V
SNR
83 dB
SINAD
83 dB
THD
–103 dB
SFDR
103 dB
ENOB
13.6 bits
Noise performance
For the peak-to-peak noise distribution test, a differential input channel is connected to AGND at the input
terminal block, and 32,000 samples are acquired at the maximum rate available at each setting.
Table 4. Noise performance specifications
Range Counts LSBrms
±10 V
11.6
1.77
±5 V
18.0
2.73
0 V to 10 V
23.3
3.54
0 V to 5 V
36.1
5.47

USB-1808X User's Guide Specifications
20
Analog output
Table 5. Analog output specifications
Parameter Condition Specification
Number of channels
2
Resolution
16 bits
Output ranges
Calibrated
±10 V
Output transient
Host computer is reset, powered on,
suspended, or a reset command is issued
to the device
Duration: 5 ms
Amplitude: 2 V p-p
Powered off from 0 V output Duration: 20 ms
Amplitude: 5 V p-p
Differential non-linearity
±0.25 LSB typ
±1 LSB max
Output current
AOUTx pins
±3.5 mA max
Output short-circuit protection
Single AOUTx channel connected to
AGND
Unlimited duration
Output coupling
DC
Power on and reset state
DACs cleared to zero-scale: 0 V, ±50 mV
Output noise
100 µVrms
Trigger source OTRIG (see External trigger on page
24)
Digital pattern detection (see Pattern
trigger on page 24)
Scan clock source Internal output scan clock or external
output scan clock (OCLKI pin)
Output update rate
0.023 Hz to 500 kHz per channel
Slew rate
15 V/µS
Throughput Software paced 33 S/s to 8,000 S/s typ, system-dependent
Hardware paced
1,000 kS/s max, system-dependent
Note 1: Leave unused AOUTx output channels disconnected.
Note 2: AOUTx defaults to 0 V whenever the host computer is reset, powered on, suspended, or a reset command is
issued to the device.
Table 6. Calibrated absolute accuracy specifications
Range Absolute accuracy (±LSB)
±10 V
16
Table 7. Calibrated absolute accuracy components specifications
Range % of
reading
Offset
(±mV)
Offset tempco
(µV/°C)
Gain tempco
(ppm of range/°C)
±10 V
0.0183
1.831
4.7
9.4
Table 8. Relative accuracy specifications (±LSB)
Range Relative accuracy (INL)
±10 V
1.0