Measurement Computing USB-1208FS-Plus-OEM User manual

USB-1208FS-Plus-OEM
Analog and Digital I/O
Trademark and Copyright Information
User's Guide
January 2019. Rev 3
© Measurement Computing Corporation

HM USB-1208FS-Plus-OEM.docx
Measurement Computing Corporation, InstaCal, Universal Library, and the Measurement Computing logo are
either trademarks or registered trademarks of Measurement Computing Corporation. Refer to the Copyrights &
Trademarks section on mccdaq.com/legal for more information about Measurement Computing trademarks.
Other product and company names mentioned herein are trademarks or trade names of their respective
companies.
© 2019 Measurement Computing Corporation. All rights reserved. No part of this publication may be
reproduced, stored in a retrieval system, or transmitted, in any form by any means, electronic, mechanical, by
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
Conventions........................................................................................................................................................5
Where to find more information.........................................................................................................................5
Chapter 1
Introducing the USB-1208FS-Plus-OEM .............................................................................................6
Functional block diagram...................................................................................................................................6
Chapter 2
Installing the USB-1208FS-Plus-OEM .................................................................................................7
Unpacking...........................................................................................................................................................7
Downloading the software..................................................................................................................................7
Installing the hardware .......................................................................................................................................7
Installing on a Windows platform..................................................................................................................................... 7
Calibrating the hardware.....................................................................................................................................7
Chapter 3
Functional Details .................................................................................................................................8
Analog input acquisition modes .........................................................................................................................8
Software paced.................................................................................................................................................................. 8
Hardware paced ................................................................................................................................................................ 8
Board components..............................................................................................................................................9
USB connector.................................................................................................................................................................. 9
LED .................................................................................................................................................................................. 9
Header connectors............................................................................................................................................................. 9
Differential mode pinout..................................................................................................................................................10
Single-ended mode pinout ...............................................................................................................................................10
Signal connections............................................................................................................................................11
Analog input....................................................................................................................................................................11
Analog output ..................................................................................................................................................................13
Digital I/O........................................................................................................................................................................13
Counter input ...................................................................................................................................................................15
External trigger input.......................................................................................................................................................15
SYNC I/O ........................................................................................................................................................................15
Power output....................................................................................................................................................................15
Ground.............................................................................................................................................................................15
Accuracy...........................................................................................................................................................15
Synchronized operations...................................................................................................................................18
Power................................................................................................................................................................18
Mechanical drawings........................................................................................................................................18
Chapter 4
Specifications......................................................................................................................................19
Analog input.....................................................................................................................................................19
Accuracy..........................................................................................................................................................................20
Noise performance...........................................................................................................................................................20
Analog output ...................................................................................................................................................21
Digital input/output...........................................................................................................................................21
External trigger.................................................................................................................................................22
External clock input/output...............................................................................................................................22
Counter.............................................................................................................................................................23
Memory ............................................................................................................................................................23

USB-1208FS-Plus-OEM User's Guide
4
Microcontroller.................................................................................................................................................23
Power................................................................................................................................................................23
General .............................................................................................................................................................24
Environmental ..................................................................................................................................................24
Mechanical .......................................................................................................................................................24
Signal connector...............................................................................................................................................24
Differential mode signals.................................................................................................................................................25
Single-ended mode signals...............................................................................................................................................25

5
Preface
About this User's Guide
This document describes the Measurement Computing USB-1208FS-Plus-OEM data acquisition device and
lists device specifications.
Conventions
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 the 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 USB-1208FS-Plus-OEM 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-1208FS-Plus-OEM
The USB-1208FS-Plus-OEM is a USB 2.0 full-speed analog input and digital I/O data acquisition device that
provides the following features:
Eight analog input channels that are software-selectable for either eight 11-bit single-ended inputs or four
12-bit differential inputs
Two 12-bit analog output channels
16 digital I/O channels that are independently-selectable as input or output in two 8-bit ports
32-bit event counter input for counting TTL pulses
External digital trigger input
Bidirectional external clock for synchronous operation with more than one device.
Two header connectors for field wiring connections
The USB-1208FS-Plus-OEM device is compatible with both USB 1.1 and USB 2.0 ports. The speed of the
device may be limited when using a USB 1.1 port due to the difference in transfer rates on the USB 1.1 versions
of the protocol (low-speed and full-speed).
The device is powered by the +5 V USB supply from the computer. No external power is required.
Caution! There are no product safety, electromagnetic compatibility (EMC), or CE marking compliance
claims made for the USB-1208FS-Plus-OEM. The USB-1208FS-Plus-OEM is intended for use as
a component of a larger system. MCC can help developers meet their compliance requirements.
The end product supplier, however, is responsible for conforming to any and all compliance
requirements.
Functional block diagram
Device functions are illustrated in the block diagram shown here.
Figure 1. USB-1208FS-Plus-OEM functional block diagram

7
Chapter 2
Installing the USB-1208FS-Plus-OEM
Unpacking
As with any electronic device, you should take care while handling to avoid damage from static
electricity. Before removing the board 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.
Downloading the software
Refer to the USB-1208FS-Plus-OEM product page on the Measurement Computing website for information
about the software that supports the device.
Install the software before you install the hardware
The driver needed to run the device is installed when you install the software. Therefore, you need to install
software before you install hardware.
Installing the hardware
Installing on a Windows platform
Connect the USB-1208FS-Plus-OEM to a to an available USB port on the computer running Windows, 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 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 device LED turns on after the device is
successfully installed.
If the LED turns off
If communication is lost between the device and the computer, the 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.
The USB-1208FS-Plus-OEM does not support field calibration.

8
Chapter 3
Functional Details
Analog input acquisition modes
The USB-1208FS-Plus-OEM can acquire analog input data in either software paced or hardware paced mode.
Software paced
The USB-1208FS-Plus-OEM acquires data one analog sample at a time using software paced mode. You
initiate the A/D conversion by calling a software command. The analog value is converted to digital and
returned to the computer. You can repeat this procedure until you have the total number of samples that you
want.
The maximum sample rate in software-paced mode is system-dependent.
Hardware paced
The USB-1208FS-Plus-OEM can acquire data from up to eight channels using hardware-paced mode. The
analog data is acquired and converted to digital values until you stop the scan. Data is transferred in blocks of
32 samples from the device to the memory buffer on your computer.
The A/D converter is paced by either an internal or external clock source.
The maximum sample rate is an aggregate rate. The total sample rate for all channels cannot exceed 50 kS/s.
The following table lists the sample rate when scanning from one to eight channels.
Maximum per channel sample rate
# channels
scanned Sample rate (kS/s)
1
50
2
25
3
16.70
4
12.50
5
10
6
8.30
7
7.14
8
6.25
You can start a hardware-paced scan with a software command. Optionally, hardware-paced scans can be
delayed by an external hardware trigger event.

USB-1208FS-Plus-OEM User's Guide Functional Details
9
Board components
The board components – header connectors, LED, and USB connector –are shown in Figure 2.
1
Header connector pins 21 to 40
3
USB connector
2 LED 4 Header connector pins 1 to 20
Figure 2. Board components
USB connector
Receives the supplied USB cable. When connected to a computer or USB hub, the cable provides power and
communication. No external power supply is required.
LED
The following table lists the behavior of the device LED.
LED state Indication
Steady green
The device is connected to a computer or external USB hub.
Blinks continuously Data is being transferred.
Header connectors
The header connectors provide the following connections:
Eight analog input connections (CH0 IN to CH7 IN, CH0 IN HI/LO through CH3 IN HI/LO)
Two analog output connections (D/A OUT 0 to D/A OUT 1)
16 digital I/O connections (PortA0 to Port A7, and Port B0 to Port B7)
External trigger input (TRIG_IN)
External counter input (CTR)
Bidirectional terminal for external clocking or multi-unit synchronization (SYNC)
Power output (+VO)
Analog ground (AGND) and ground (GND)
The differential and single-ended mode pinouts are shown in the following tables.

USB-1208FS-Plus-OEM User's Guide Functional Details
10
Differential mode pinout
Four-channel differential mode pinout
Pin
Signal name
Pin description
Pin
Signal name
Pin description
1
CH0 IN HI
Analog input 0+
21
Port A0
Port A bit 0
2
CH0 IN LO
Analog input 0–
22
Port A1
Port A bit 1
3
AGND
Analog ground
23
Port A2
Port A bit 2
4
CH1 IN HI
Analog input 1+
24
Port A3
Port A bit 3
5
CH1 IN LO
Analog input 1–
25
Port A4
Port A bit 4
6
AGND
Analog ground
26
Port A5
Port A bit 5
7
CH2 IN HI
Analog input 2+
27
Port A6
Port A bit 6
8
CH2 IN LO
Analog input 2–
28
Port A7
Port A bit 7
9
AGND
Analog ground
29
GND
Ground
10 CH3 IN HI Analog input 3+ 30 +VO Power output
11
CH3 IN LO
Analog input 3–
31
GND
Ground
12 AGND Analog ground 32 Port B0 Port B bit 0
13
D/A OUT 0
Analog output 0
33
Port B1
Port B bit 1
14
D/A OUT 1
Analog output 1
34
Port B2
Port B bit 2
15
AGND
Analog ground
35
Port B3
Port B bit 3
16
Reserved
Reserved for future use
36
Port B4
Port B bit 4
17
GND
Ground
37
Port B5
Port B bit 5
18
TRIG_IN
Trigger input
38
Port B6
Port B bit 6
19
SYNC
Synchronization I/O
39
Port B7
Port B bit 7
20
CTR
Counter input
40
GND
Ground
USB connector
Single-ended mode pinout
Eight-channel single-ended mode pinout
Pin
Signal name
Pin description
Pin
Signal name
Pin description
1
CH0 IN
Analog input 0
21
Port A0
Port A bit 0
2
CH1 IN
Analog input 1
22
Port A1
Port A bit 1
3
AGND
Analog ground
23
Port A2
Port A bit 2
4
CH2 IN
Analog input 2
24
Port A3
Port A bit 3
5
CH3 IN
Analog input 3
25
Port A4
Port A bit 4
6
AGND
Analog ground
26
Port A5
Port A bit 5
7
CH4 IN
Analog input 4
27
Port A6
Port A bit 6
8
CH5 IN
Analog input 5
28
Port A7
Port A bit 7
9
AGND
Analog ground
29
GND
Ground
10
CH6 IN
Analog input 6
30
+VO
Power output
11
CH7 IN
Analog input 7
31
GND
Ground
12
AGND
Analog ground
32
Port B0
Port B bit 0
13
D/A OUT 0
Analog output 0
33
Port B1
Port B bit 1
14
D/A OUT 1
Analog output 1
34
Port B2
Port B bit 2
15
AGND
Analog ground
35
Port B3
Port B bit 3
16
Reserved
Reserved for future use
36
Port B4
Port B bit 4
17
GND
Ground
37
Port B5
Port B bit 5
18
TRIG_IN
Trigger input
38
Port B6
Port B bit 6
19
SYNC
Synchronization I/O
39
Port B7
Port B bit 7
20 CTR Counter input 40 GND Ground
USB connector

USB-1208FS-Plus-OEM User's Guide Functional Details
11
Signal connections
Analog input
You can connect up to eight analog input connections to the header connector pins 1 to 20.
You can configure the analog input channels as eight single-ended channels (CH0 IN through CH7 IN)or four
differential channels (CH0 IN HI/LO through CH3IN HI/LO). When configured for differential mode, each
analog input has 12-bit resolution. When configured for single-ended mode, each analog input has 11-bit
resolution, due to restrictions imposed by the A/D converter.
Single-ended configuration
When configured for single-ended input mode, the input signal is referenced to signal ground (GND) and
delivered through two wires:
Connect the wire carrying the signal to be measured to CH# IN.
Connect the second wire to AGND.
The input range for single-ended mode is ±10 V. The single-ended mode pinout is shown in on page 10.
Differential configuration
When configured for differential input mode, the input signal is measured with respect to the low input and
delivered through three wires:
Connect the wire carrying the signal to be measured to CH# IN HI.
Connect the wire carrying the reference signal to CH# IN LO.
Connect the third wire to GND.
The differential mode pinout is shown in on page 10.
Note: To perform a single-ended measurement using differential channels, connect the signal to CH# IN HI and
ground the associated CH# IN LO input.
A low-noise precision programmable gain amplifier (PGA) is available on differential channels to provide gains
of up to 20 and a dynamic range of up to 12-bits. Differential mode input voltage ranges are ±20 V, ±10 V,
±5 V, ±4 V, ±2.5 V, ±2.0 V, ±1.25 V, and ±1.0 V.
In differential mode, the following two requirements must be met for linear operation:
Any analog input must remain in the −10V to +20V range with respect to ground at all times.
The maximum differential voltage on any given analog input pair must remain within the selected voltage
range.
The input [common-mode voltage + signal] of the differential channel must be in the −10 V to +20 V range in
order to yield a useful result.

USB-1208FS-Plus-OEM User's Guide Functional Details
12
For example, you input a 4 V pp sine wave to CH# IN HI, and apply the same sine wave 180° out of phase to
CH# IN LO. The common mode voltage is 0 V. The differential input voltage swings from 4 V – (–4 V) = 8 V
to –4 V – (4 V) = –8V. Both inputs satisfy the –10 V to +20 V input range requirement, and the differential
voltage is suited for the ±10 V input range (see Figure 3).
Figure 3. Differential voltage example: common mode voltage of 0 V
If you increase the common mode voltage to 11 V, the differential remains at 8 V. Although the [common-mode
voltage + signal] on each input now has a range of +7 V to +15 V, both inputs still satisfy the –10 V to +20 V
input requirement (see Figure 4).
Figure 4. Differential voltage example: common mode voltage of 11 V
If you decrease the common-mode voltage to –7 V, the differential stays at 8 V. However, the solution now
violates the input range condition of –10 V to +20 V. The voltage on each analog input now swings from –3 V
to –11 V. Voltages between –10 V and –3 V are resolved, but those below -10 V are clipped, as shown in
Figure 5.
Figure 5. Differential voltage example: common mode voltage of –7 V
Since the analog inputs are restricted to a −10 V to +20 V signal swing with respect to ground, all ranges except
±20V can realize a linear output for any differential signal with zero common mode voltage and full scale signal
inputs. The ±20 V range is the exception. You cannot put −20 V on CH# IN HI and 0 V on CH# IN LO, since
this violates the input range criteria.

USB-1208FS-Plus-OEM User's Guide Functional Details
13
The table below shows some possible inputs and the expected results.
Sample inputs and differential results
CH# IN HI CH# IN LO Result
–20 V
0 V
Invalid
–15 V
+5 V
Invalid
–10 V
0 V
–10 V
–10 V
+10 V
–20 V
0 V
+10 V
–10 V
0 V
+20 V
–20 V
+10 V
–10 V
+20 V
+10 V
0 V
+10 V
+15 V
–5 V
+20 V
+20 V
0
+20 V
Channel-Gain queue
The channel gain queue feature allows you to set up a scan sequence with a unique per-channel gain setting and
channel sequence. The settings are stored in a channel-gain queue list that is written to local memory on the
device. The gain queue can contain up to eight elements in single-ended mode, and up to four elements in
differential mode.
The elements must be unique and listed in ascending order. An example of a three-element list is shown in the
table below.
Sample channel-gain queue list
Element Channel Range Gain
0
CH0
BIP10V
2
1 CH1 BIP20V 1
2
CH3
BIP4V
5
When a scan begins with the gain queue enabled, the device reads the first element, sets the appropriate channel
number, range, and gain, and then acquires a sample. The properties of the next element are then retrieved, and
another sample is acquired. This sequence continues until all elements in the gain queue have been selected.
When the end of the channel list is detected, the sequence returns to the first element in the list. The sequence
repeats until the specified number of samples is acquired.
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.
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 from www.mccdaq.com/support/DAQ-Signal-Connections.aspx.)
Analog output
You can connect up to two analog output connections to D/A OUT 0 and D/A OUT 1. Each channel can be paced
at rates up to 50,000 updates per second. The output range is 0 V to 5 V.
Digital I/O
The device has 16 DIO channels that are configured as two 8-bit ports – Port A and Port B. Port B is high drive.
You can connect up to eight DIO lines to Port A0 to Port A7 and up to eight DIO lines to Port B0 to Port B7.
You can configure each port for either input or output. The digital ports are set for input when the device is
powered on or reset.

USB-1208FS-Plus-OEM User's Guide Functional Details
14
When configured for input, the digital I/O terminals can detect the state of any TTL-level. Refer to the
schematic shown in Figure 6.
Figure 6. Schematic showing switch detection by digital channel Port A0
If you set the switch to the +5V input, Port A0 reads TRUE (1). When set to GND, Port A0 reads FALSE (0).
Pull-up/down configuration
All digital I/O lines are pulled high to USB +5 V with a 47 kΩ resistor by 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.
Complete the following steps to set the jumper for pull-up or pull-down:
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-1208FS-Plus-OEM 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 three screws from the bottom of the device using a #1 Philips head screwdriver.
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.
The user-configurable jumpers are labeled DIO A and DIO B. Figure 7 shows the location of each jumper on
the circuit board.
1
DIO B jumper
2
DIO A jumper
Figure 7. Pull-up/down jumper locations
5. Set each jumper for pull-up (P/UP) or pull-down (P/DN), as shown in Figure 8. Use the jumper labeled
DIO A to configure Port A, and DIO B to configure Port B.
Figure 8. Pull-up/down jumper configuration
6. Replace the top section of the housing, and fasten it to the bottom section with the three screws.

USB-1208FS-Plus-OEM User's Guide Functional Details
15
For more information about digital signal connections
For more information about digital signal connections, refer to the Guide to DAQ Signal Connections (available
for download from www.mccdaq.com/support/DAQ-Signal-Connections.aspx.)
Counter input
The CTR connection is input to the 32-bit external event. The internal counter increments when the TTL levels
transition from low to high. The counter can count frequencies of up to 1 MHz.
External trigger input
The TRIG_IN connection is an external trigger input that you can configure for either rising or falling edge.
SYNC I/O
The SYNC terminal is a bidirectional I/O signal that can be configured as an input (default) or an output.
Configure as an external clock input to pace the A/D conversions from an external source. The SYNC
terminal supports TTL-level input signals of up to 50 kHz.
Configure as an output to pace the conversions on a second device and acquire data from 16 channels using
one clock. For more information about synchronized operations see page 18.
Power output
The +VO connection draws power from the USB connector on the computer.
Caution! The +VO terminal is an output. Do not connect it to an external power supply or you may damage
the device and possibly the computer.
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 sync
channels and the power terminal.
Accuracy
The overall accuracy of any instrument is limited by the error components within the system. Resolution is
often incorrectly used to quantify the performance of a measurement product. While "12-bits" or "1 part in
4,096" does indicate what can be resolved, it provides little insight into the quality of an absolute measurement.
Accuracy specifications describe the actual results that can be realized with a measurement device.
There are three types of errors which affect the accuracy of a measurement system:
offset
gain
nonlinearity
The primary error sources are offset and gain. Nonlinearity is small in each device, and is not significant as an
error source with respect to offset and gain.

USB-1208FS-Plus-OEM User's Guide Functional Details
16
Figure 9 shows an ideal, error-free transfer function. The typical calibrated accuracy is range-dependent. Refer
to the Accuracy specifications on page 20 for more information. We use a ±10 V range here as an example of
what you can expect when performing a measurement in this range.
Figure 9. Ideal ADC transfer function
The offset error is measured at mid-scale. Ideally, a zero volt input should produce an output code of 2048. Any
deviation from this is an offset error.
Figure 10 shows an example of a transfer function with a ±9.77 mV offset error. Offset error affects all codes
equally by shifting the entire transfer function up or down along the input voltage axis.
The accuracy plots in Figure 10 are drawn for clarity and are not drawn to scale.
Figure 10. ADC transfer function with offset error
Gain error is a change in the slope of the transfer function from the ideal, and is typically expressed as a
percentage of full-scale.

USB-1208FS-Plus-OEM User's Guide Functional Details
17
Figure 11 shows the transfer function with gain error. Gain error is easily converted to voltage by multiplying
the full-scale (FS) input by the error.
The accuracy plots in Figure 11 are drawn for clarity and are not drawn to scale.
Figure 11. ADC Transfer function with gain error
For example, the USB-1208FS-Plus-OEM exhibits a typical calibrated gain error of ±0.2% on all ranges. For
the ±10 V range, this would yield 10 V × ±0.002 = ±20 mV. This means that at full scale, and neglecting the
effect of offset, the measurement would be within 20 mV of the actual value. Note that gain error is expressed
as a ratio. Values near ±FS are more affected from an absolute voltage standpoint than are values near mid-
scale, which see little or no voltage error.
Combining these two error sources in Figure 12, we have a plot of the error band for the ±10 V range. This is a
graphical version of the typical accuracy specification of the product.
The accuracy plots in Figure 12 are drawn for clarity and are not drawn to scale.
Figure 12. Error band plot

USB-1208FS-Plus-OEM User's Guide Functional Details
18
Synchronized operations
You can connect the SYNC pin of two devices together in a master/slave configuration and acquire data from
the analog inputs of both devices using one clock.
When the SYNC pin is configured as an output, the internal A/D pacer clock signal is sent to the header
connector. Output the clock signal to the SYNC pin of a second device that is configured for A/D pacer input.
Power
Connecting the device to a computer draws <100 mA of current from the USB +5V supply. When running
applications, the current that can be drawn from all device connections (analog, digital, SYNC, and +VO output
loading) is <500 mA. The maximum output current that is available at the +VO power output terminal is
100 mA.
With all outputs at their maximum output current, the USB-1208FS-Plus-OEM in a fully-loaded configuration
may be above that allowed by the computer. In this case, determine the per-pin loading in the application to
ensure that the maximum loading criteria is met. The per-pin loading is calculated by dividing +5V by the load
impedance of the pin in question.
Mechanical drawings
Figure 13. Circuit board dimensions

19
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. Analog input specifications
Parameter Condition Specification
A/D converter type
Successive approximation type
Input voltage range for linear operation
CHx to GND
Single-ended mode: ±10 V max
Differential mode: –10 V min, +20 V max
Absolute maximum input voltage
CHx to GND
±28 V max
Input impedance
122 kΩ
Input current (Note 1)
Vin = +10 V
70 µA typ
V
in
= 0 V
–12 µA typ
V
in
= –10 V
–94 µA typ
Number of channels 8 single-ended or 4 differential; software-selectable
Input ranges
Single-ended
±10 V, G=2
Differential
±20 V, G=1
±10 V, G=2
±5 V, G=4
±4 V, G=5
±2.5 V, G=8
±2.0 V, G=10
±1.25 V, G=16
±1.0 V, G=20
Software-selectable
Throughput (Note 2)
Software paced
250 S/s typ, PC-dependent
Continuous scan
0.014 S/s to 50 kS/s
Channel gain queue Software selectable. 8 elements in SE mode,
4 elements in DIFF mode.
One gain element per channel. Elements must be
unique and listed in ascending order.
Resolution (Note 3) Differential 12 bits, no missing codes
Single-ended
11 bits
Integral linearity error
±1 LSB typ
Differential linearity error
±0.5 LSB typ
Repeatability
±1 LSB typ
Trigger source Software-selectable External digital: TRIG_IN
Software-selectable
Pacer source
Software-selectable

Internal
External (SYNC), rising edge triggered
Software-selectable
Note 1: Input current is a function of applied voltage on the analog input channels. For a given input voltage, Vin, the
input leakage is approximately equal to (8.181 * Vin – 12) µA.
Note 2: Maximum throughput when scanning is machine dependent.
Note 3: The AD7870 converter only returns 11 bits (0 to 2,047 codes) in single-ended mode.

USB-1208FS-Plus-OEM User's Guide Specifications
20
Accuracy
Table 2. Accuracy, differential mode
Range Accuracy (LSB)
±20 V
5.1
±10 V
6.1
±5 V
8.1
±4 V
9.1
±2.5 V
12.1
±2 V 14.1
±1.25 V
20.1
±1 V
24.1
Table 3. Accuracy, single-ended mode
Range Accuracy (LSB)
±10 V
4.0
Table 4. Accuracy components, differential mode – all values are (±)
Range % of Reading Gain Error at FS (mV) Offset (mV) Accuracy at FS (mV)
±20 V
0.2
40
9.766
49.766
±10 V
0.2
20
9.766
29.766
±5 V
0.2
10
9.766
19.766
±4 V
0.2
8
9.766
17.766
±2.5 V
0.2
5
9.766
14.766
±2 V 0.2 4 9.766 13.766
±1.25 V
0.2
2.5
9.766
12.266
±1 V
0.2
2
9.766
11.766
Table 5. Accuracy components, single-ended mode – all values are (±)
Range % of Reading Gain Error at FS (mV) Offset (mV) Accuracy at FS (mV)
±10 V
0.2
20
19.531
39.531
Noise performance
Table 6. Noise performance, differential mode
Range Typical counts LSBrms
±20 V
2
0.30
±10 V
2
0.30
±5 V
3
0.45
±4 V
3
0.45
±2.5 V
4
0.61
±2 V
5
0.76
±1.25 V
7
1.06
±1 V
8
1.21
Table 7. Noise performance, single-ended mode
Range Typical counts LSBrms
±10 V
2
0.30