Measurement Computing USB-5201 User manual

USB-5201
USB-based 8-Channel Thermocouple Input
Device and Data Logger
User's Guide
Document Revision 7, June, 2008
© Copyright 2008, Measurement Computing Corporation

3
HM USB-5201.doc
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4
Trademark and Copyright Information
TracerDAQ, Universal Library, Harsh Environment Warranty, Measurement Computing Corporation, and the Measurement
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Notice
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5
Table of Contents
Preface
About this User’s Guide .......................................................................................................................7
What you will learn from this user’s guide.........................................................................................................7
Conventions in this user’s guide.........................................................................................................................7
Where to find more information.........................................................................................................................7
Chapter 1
Introducing the USB-5201....................................................................................................................8
Overview: USB-5201 features............................................................................................................................8
Logging data with the USB-5201 ..................................................................................................................................... 8
USB-5201 block diagram...................................................................................................................................9
Software features................................................................................................................................................9
Connecting a USB-5201 to your computer is easy...........................................................................................10
Chapter 2
Installing the USB-5201......................................................................................................................11
What comes with your USB-5201 shipment?...................................................................................................11
Hardware .........................................................................................................................................................................11
Additional documentation................................................................................................................................................12
Unpacking the USB-5201.................................................................................................................................12
Installing the software ......................................................................................................................................12
Installing the hardware .....................................................................................................................................12
Firmware revision 2.12 and earlier ..................................................................................................................................12
Firmware revision 3.0 and later .......................................................................................................................................12
Configuring the USB-5201...............................................................................................................................13
Configuring data logging options.....................................................................................................................................13
Calibrating the USB-5201 ................................................................................................................................13
Chapter 3
Sensor Connections...........................................................................................................................14
Screw terminal pin out......................................................................................................................................14
Thermocouple input terminals (C0H/C0L to C7H/C7L) .................................................................................................15
Ground terminals (GND).................................................................................................................................................15
Power terminals (+5V).....................................................................................................................................................15
Digital terminals (DIO0 to DIO7)....................................................................................................................................15
CJC sensors......................................................................................................................................................................16
Thermocouple connections...............................................................................................................................16
Wiring configuration........................................................................................................................................................16
Digital I/O connections.....................................................................................................................................17
Configuring the DIO channels to generate alarms...........................................................................................................17
Chapter 4
Functional Details...............................................................................................................................18
Thermocouple measurements...........................................................................................................................18
Cold junction compensation (CJC)..................................................................................................................................18
Data linearization.............................................................................................................................................................18
Open-thermocouple detection (OTD) ..............................................................................................................................18
External components ........................................................................................................................................19
Screw terminals................................................................................................................................................................19
USB connector.................................................................................................................................................................19
LED .................................................................................................................................................................................19
CompactFlash®memory card slot....................................................................................................................................20
Data logging button .........................................................................................................................................................20
External power supply......................................................................................................................................21

USB-5201 User's Guide
6
Disconnecting the USB-5201 from the computer.............................................................................................21
Transferring binary data after a logging session...............................................................................................21
Converting binary data after a logging session.................................................................................................21
Chapter 5
Specifications......................................................................................................................................22
Analog input section.........................................................................................................................................22
Channel configurations.....................................................................................................................................22
Accuracy...........................................................................................................................................................23
Thermocouple measurement accuracy.............................................................................................................................23
Throughput rate to PC ......................................................................................................................................23
Digital input/output...........................................................................................................................................24
Temperature alarms..........................................................................................................................................24
Memory ............................................................................................................................................................24
Microcontroller.................................................................................................................................................25
Data Logging....................................................................................................................................................25
Real time clock.................................................................................................................................................26
USB +5V voltage .............................................................................................................................................26
Power................................................................................................................................................................26
USB specifications ...........................................................................................................................................27
Environmental ..................................................................................................................................................27
Mechanical .......................................................................................................................................................27
Screw terminal connector type and pin out.......................................................................................................27
Screw terminal pin out.....................................................................................................................................................28
Declaration of Conformity..................................................................................................................29

7
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-5201 so that you get the most out of its
USB-based temperature measurement features.
This user’s guide also refers you to related documents available on our web site, and to technical support
resources that can also help you get the most out of these boards.
Conventions in this user’s guide
For more information on …
Text presented in a box signifies additional information and helpful hints related to the subject matter you are
reading.
Caution! Shaded caution statements present information to help you avoid injuring yourself and others,
damaging your hardware, or losing your data.
< : > Angle brackets that enclose numbers separated by a colon signify a range of numbers, such as those assigned
to registers, bit settings, etc.
bold text Bold text is used for the names of objects on the screen, such as buttons, text boxes, and check boxes. For
example:
1. Insert the disk or CD and click the OK button.
italic text Italic text is used for the names of manuals and help topic titles, and to emphasize a word or phrase. For
example:
The InstaCal installation procedure is explained in the Quick Start Guide.
Never touch the exposed pins or circuit connections on the board.
Where to find more information
MCC's Specifications: USB-5201 (the PDF version of the Specifications chapter in this guide) is available
on our web site at www.mccdaq.com/pdfs/USB-5201.pdf.
MCC's Quick Start Guide is available on our web site at
www.mccdaq.com/PDFmanuals/DAQ-Software-Quick-Start.pdf.
MCC's Guide to Signal Connections is available on our web site at
www.mccdaq.com/signals/signals.pdf.
MCC's Universal Library User's Guide is available on our web site at
www.mccdaq.com/PDFmanuals/sm-ul-user-guide.pdf.
MCC's Universal Library Function Reference is available on our web site at
www.mccdaq.com/PDFmanuals/sm-ul-functions.pdf.
MCC's Universal Library for LabVIEW™User’s Guide is available on our web site at
www.mccdaq.com/PDFmanuals/SM-UL-LabVIEW.pdf.
USB-5201 User's Guide (this document) is also available on our web site at
www.mccdaq.com/PDFmanuals/USB-5201.pdf.

8
Chapter 1
Introducing the USB-5201
Overview: USB-5201 features
This user's guide contains all of the information you need to connect the USB-5201 to your computer and to the
signals you want to measure.
The USB-5201 is a USB 2.0 full-speed, thermocouple input device that is supported under popular Microsoft®
Windows®operating systems. The USB-5201 is fully compatible with both USB 1.1 and USB 2.0 ports.
The USB-5201 provides eight differential thermocouple input channels and two integrated cold junction
compensation (CJC) sensors. You can take measurements from type J, K, R, S, T, N, E, and B thermocouples.
An open thermocouple detection feature lets you detect a broken thermocouple. An on-board microprocessor
automatically linearizes the measurement data.
Eight independent, TTL-compatible digital I/O channels are provided to monitor TTL-level inputs,
communicate with external devices, and to generate alarms. The digital I/O channels are software
programmable for input or output.
The USB-5201 features eight independent temperature alarms. Each alarm controls an associated digital I/O
channel as an alarm output. The input to each alarm is one of the temperature input channels. The output of each
alarm is software configurable as active high or low. You set up the temperature threshold conditions to activate
each alarm. When an alarm is activated, the associated DIO channel is driven to the output state.
You can log your measurements to a CompactFlash®memory card. CompactFlash is a removable non-volatile
storage device. A 256 MB CompactFlash memory card is shipped with the device to store your data. For more
information, refer to the section "Logging data with the USB-5201" below.
External power is required for data logging operations
Due to processing limitations, you cannot log data to the memory card when the USB-5201 is connected to your
computer's active USB bus. When operating as a data logger, disconnect the USB cable from the computer, and
connect the external power supply shipped with the device.
The USB-5201 is a standalone plug-and-play device. External power is required for data logging mode only. All
configurable options are software-programmable. The USB-5201 is fully software-calibrated.
Logging data with the USB-5201
The USB-5201 has many software-configurable options for setting up data logging.
You can record:
temperature ( C) or raw data from selected input channels
timestamp data
CJC sensor readings
You specify the number of seconds between samples. You can begin logging data at power up, when you press
the data logging button, or at a specific date and time.

USB-5201 User's Guide Introducing the USB-5201
9
USB-5201 block diagram
USB-5201 functions are illustrated in the block diagram shown here.
24-bit A/D
(CH0, CH1) Input
mux.
Input
mux.
CJC
CH0-3
Precision
5V Ref.
24-bit A/D
(CH2, CH3)
24-bit A/D
(CH4, CH5) Input
mux.
Input
mux.
CJC
CH4-7
24-bit A/D
(CH6, CH7)
Screw Terminal
Screw Terminal
Isolated
Micro
Temp
sensor
I/O
Isolator
500 V
Isolation
Barrier
SPI
Isolated
DC/DC
USB
+5V
(+12)
(-12)
8
DIO
Compact
Flash
connector
Battery-backed
Real-Time
Clock
USB
Microcontroller
USB
(PC)
Ext. Pwr.
(for data
logging)
USB
or
External power required
for data logging operations
Figure 1. USB-5201 functional block diagram
Software features
For information on the features of InstaCal and the other software included with your USB-5201, refer to the
Quick Start Guide that shipped with your device. The Quick Start Guide is also available in PDF at
www.mccdaq.com/PDFmanuals/DAQ-Software-Quick-Start.pdf.
Check www.mccdaq.com/download.htm for the latest software version.

USB-5201 User's Guide Introducing the USB-5201
10
Connecting a USB-5201 to your computer is easy
Installing a data acquisition device has never been easier.
The USB-5201 relies upon the Microsoft Human Interface Device (HID) class drivers. The HID class
drivers ship with every copy of Windows that is designed to work with USB ports. We use the Microsoft
HID because it is a standard, and its performance delivers full control and maximizes data transfer rates for
your USB-5201. No third-party device driver is required.
In addition to utilizing the HID class drivers, the USB-5201 also utilizes the Mass Storage Device interface
to allow the CompactFlash Card adapter to appear as a storage device. This feature allows direct access to
data files stored on the USB-5201.
The USB-5201 is plug-and-play. There are no jumpers to position, DIP switches to set, or interrupts to
configure.
You can connect the USB-5201 before or after you install the software, and without powering down your
computer first. When you connect an HID to your system, your computer automatically detects it and
configures the necessary software. You can connect and power multiple HID peripherals to your system
using a USB hub.
You can connect your system to various devices using a standard four-wire cable. The USB connector
replaces the serial and parallel port connectors with one standardized plug and port combination.
You do not need a separate power supply device. The USB automatically delivers the electrical power
required by each peripheral connected to your system. However, for data logging operations, an external
power supply is required.
Data can flow two ways between a computer and peripheral over USB connections.

11
Chapter 2
Installing the USB-5201
What comes with your USB-5201 shipment?
The following items are shipped with the USB-5201.
Hardware
The following items should be included with your shipment.
USB-5201 with memory card
USB cable (2 meter length)
External power supply –2.5 watt USB adapter for data logging operations.
MCC part number USB Power Adapter.

USB-5201 User's Guide Installing the USB-5201
12
Additional documentation
In addition to this hardware user's guide, you should also receive the Quick Start Guide (available in PDF at
www.mccdaq.com/PDFmanuals/DAQ-Software-Quick-Start.pdf). This booklet supplies a brief description of
the software you received with your USB-5201 and information regarding installation of that software. Please
read this booklet completely before installing any software or hardware.
Unpacking the USB-5201
As with any electronic device, you should take care while handling to avoid damage from static
electricity. Before removing the USB-5201 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 your USB-5201 is damaged, notify Measurement Computing Corporation immediately by phone, fax, or e-
mail. For international customers, contact your local distributor where you purchased the USB-5201.
Phone: [phone] and follow the instructions for reaching Tech Support.
Fax: [phone] to the attention of Tech Support
Email: [email protected]
Installing the software
Refer to the Quick Start Guide for instructions on installing the software on the Measurement Computing Data
Acquisition Software CD. This booklet is available in PDF at www.mccdaq.com/PDFmanuals/DAQ-Software-
Quick-Start.pdf.
Installing the hardware
To connect the USB-5201 to your system, turn your computer on, and connect the USB cable to a USB port on
your computer or to an external USB hub that is connected to your computer. The USB cable provides power
and communication to the USB-5201.
Caution! If you are connecting the USB-5201 to an external self-powered hub, connect the USB hub to the
computer before you connect the device to the hub. This ensures that the device detects the hub as
an active USB port.
Firmware revision 2.12 and earlier
When you connect the USB-5201 for the first time, a Found New Hardware popup balloon (Windows XP) or
dialog (other Windows versions) opens as the USB-5201 is detected.
When this balloon or dialog closes, the installation is complete. The LED on the side of the device should flash
and then remain lit. This indicates that communication is established between the USB-5201 and your
computer.
Firmware revision 3.0 and later
The USB-5201 installs as a composite device with separate devices attached. When you connect the USB-5201
for the first time, Found New Hardware popup balloons (Windows XP) or dialogs (other Windows version)
open as each USB-5201 interface is detected.
It is normal for multiple dialogs to open when you connect the USB-5201 for the first time. For additional
information, refer to the "Notes on installing and using the USB-5201 and USB-5203 data logging devices" that
was shipped with the USB-5201.
When the last balloon or dialog closes, the installation is complete. The LED on the USB-5201 should flash and
then remain lit. This indicates that communication is established between the USB-5201 and your computer.
Caution! Do not disconnect any device from the USB bus while the computer is communicating with the
USB-5201, or you may lose data and/or your ability to communicate with the USB-5201.

USB-5201 User's Guide Installing the USB-5201
13
If the LED turns off
If the LED is lit but then turns off, the computer has lost communication with the USB-5201. To restore
communication, disconnect the USB cable from the computer, and then reconnect it. This should restore
communication, and the LED should turn back on.
Configuring the USB-5201
All hardware configuration options on the USB-5201 are programmable with software. Use InstaCal to set the
thermocouple type for each channel. Configuration options are stored on the USB-5201 's isolated
microcontroller in EEPROM, which is non-volatile memory on the USB-5201. Configuration options are
loaded on power up. The factory default configuration is Type J thermocouple.
Warm up
Allow the USB-5201 to warm up for 30 minutes before taking measurements. This warm up time minimizes
thermal drift and achieves the specified rated accuracy of measurements.
Configuring data logging options
The following data logging configuration options are programmable with InstaCal.
select the input channels to log
set the data format
set the start mode
set up alarm conditions
copy and convert saved binary files
delete data files
All data logging options are stored on the USB-5201 in non-volatile memory in EEPROM, and are loaded on
power up.
Calibrating the USB-5201
The USB-5201 is fully calibrated with InstaCal. Calibration coefficients are stored in EEPROM. Allow the
USB-5201 to operate for at least 30 minutes before calibrating.

14
Chapter 3
Sensor Connections
The USB-5201 supports type types J, K, R, S, T, N, E, and B thermocouples.
Thermocouple selection
The thermocouple type you select depends on your application needs. Review the temperature ranges and
accuracies of each type to determine which is best suited for your application.
Screw terminal pin out
The USB-5201 has four rows of screw terminals —two rows on the top edge of the housing, and two rows on
the bottom edge. Each row has 26 connections. Between each bank of screw terminals are two integrated CJC
sensors used for thermocouple measurements. Signals are identified in Figure 2.
RSVD 1 NC 2 C0H 3 C0L 4 NC 5 C1H 7 C1L 8 GND 9 NC 12 C2H 13 C2L 14 NC 15 C3H 17 C3L 18 GND 19 +5V 21 GND 22 DIO0 23 DIO1 24 DIO2 25 DIO3 26
6
10
11
16 20
RSVD RSVD RSVD RSVD RSVD
27 RSVD 28 GND 29 C7L 30 C7H 31 32 NC 33 C6L 34 C6H 35 NC 36 37 38 GND 39 C5L 40 C5H 41 42 NC 43 C4L 44 C4H 45 NC 46 47 +5V 48 GND 49 DIO7 50 DIO6 51 DIO5 52 DIO4
RSVD RSVD RSVD RSVD RSVD
CJC Sensor
CJC Sensor
Figure 2. USB-5201 screw terminal pin numbers

USB-5201 User's Guide Sensor Connections
15
USB-5201 screw terminal descriptions
Pin
Signal Name
Pin Description
Pin
Signal Name
Pin Description
1
RSVD
Reserved, Do Not Use
27
RSVD
Reserved, Do Not Use
2
NC
Not connected
28
GND
Ground
3
C0H
CH0 sensor input (+)
29
C7L
CH7 sensor input (-)
4
C0L
CH0 sensor input (-)
30
C7H
CH7 sensor input (+)
5
NC
Not connected
31
RSVD
Reserved, Do Not Use
6
RSVD
Reserved, Do Not Use
32
NC
Not connected
7
C1H
CH1 sensor input (+)
33
C6L
CH6 sensor input (-)
8
C1L
CH1 sensor input (-)
34
C6H
CH6 sensor input (+)
9
GND
Ground
35
NC
Not connected
10
RSVD
Reserved, Do Not Use
36
RSVD
Reserved, Do Not Use
CJC sensor
CJC sensor
11
RSVD
Reserved, Do Not Use
37
RSVD
Reserved, Do Not Use
12
NC
Not connected
38
GND
Ground
13
C2H
CH2 sensor input (+)
39
C5L
CH5 sensor input (-)
14
C2L
CH2 sensor input (-)
40
C5H
CH5 sensor input (+)
15
NC
Not connected
41
RSVD
Reserved, Do Not Use
16
RSVD
Reserved, Do Not Use
42
NC
Not connected
17
C3H
CH3 sensor input (+)
43
C4L
CH4 sensor input (-)
18
C3L
CH3 sensor input (-)
44
C4H
CH4 sensor input (+)
19
GND
Ground
45
NC
Not connected
20
RSVD
Reserved, Do Not Use
46
RSVD
Reserved, Do Not Use
21
+5V
+5V output
47
+5V
+5V output
22
GND
Ground
48
GND
Ground
23
DIO0
Digital Input/output
49
DIO7
Digital Input/output
24
DIO1
Digital Input/output
50
DIO6
Digital Input/output
25
DIO2
Digital Input/output
51
DIO5
Digital Input/output
26
DIO3
Digital Input/output
52
DIO4
Digital Input/output
Use 16 AWG to 30 AWG wire for your signal connections.
Tighten screw terminal connections
When making connections to the screw terminals, fully tighten the screw. Simply touching the top of the screw
terminal is not sufficient to make a proper connection.
Thermocouple input terminals (C0H/C0L to C7H/C7L)
You can connect up to eight thermocouples to the differential sensor inputs (C0H/C0L to C7H/C7L). The USB-
5201 supports type types J, K, R, S, T, N, E, and B thermocouples.
Ground terminals (GND)
The six analog ground terminals (GND) provide a common ground for the input channels and DIO bits and are
isolated (500 VDC) from the USB GND.
Power terminals (+5V)
The two +5V output terminals are isolated (500 VDC) from the USB +5V.
Caution! Each +5V terminal is an output. Do not connect to an external power supply to these terminals or
you may damage the USB-5201 and possibly the computer.
Digital terminals (DIO0 to DIO7)
You can connect up to eight digital I/O lines to the screw terminals labeled DIO0 to DIO7. Each terminal is
software-configurable for input or output.
If a digital bit is set up as an alarm, the bit is configured for output on power-up, and assumes the state defined
by the alarm configuration.

USB-5201 User's Guide Sensor Connections
16
CJC sensors
The USB-5201 has two built in high-resolution temperature sensors. One sensor is located on the right side of
the package, and one sensor is located on the left side.
Thermocouple connections
A thermocouple consists of two dissimilar metals that are joined together at one end. When the junction of the
metals is heated or cooled, a voltage is produced that correlates to temperature.
The USB-5201 makes fully-differential thermocouple measurements without the need of ground-referencing
resistors. A 32-bit floating point value in either a voltage or temperature format is returned by software. An
open thermocouple detection feature is available for each analog input which automatically detects an open or
broken thermocouple.
Use InstaCal to select the thermocouple type (J, K, R, S, N. E, and B) and one or more sensor input channels to
connect the thermocouple.
Wiring configuration
Connect the thermocouple to the USB-5201 using a differential configuration, as shown in Figure 3.
RSVD NC C#H C#L NC RSVD C#H C#L GND RSVD
Figure 3. Typical thermocouple connection
Connect thermocouples to the USB-5201 such that they are floating with respect to GND (pins 9, 19, 28, 38).
The USB-5201 GND pins are isolated from earth ground, so you can connect thermocouple sensors to voltages
referenced to earth ground as long as the isolation between the GND pins (9, 19, 28, 38) and earth ground is
maintained.
When thermocouples are attached to conductive surfaces, the voltage differential between multiple
thermocouples must remain within ±1.4 V. For best results, you should use insulated or ungrounded
thermocouples when possible.
Maximum input voltage between analog input and ground
The absolute maximum input voltage between an analog input and the isolated GND pins is ±25 VDC when the
USB-5201 is powered on, and ±40 VDC when the USB-5201 is powered off.
If you need to increase the length of your thermocouple, use the same type of thermocouple wires to minimize
the error introduced by thermal EMFs.

USB-5201 User's Guide Sensor Connections
17
Digital I/O connections
You can connect up to eight digital I/O lines to the screw terminals labeled DIO0 to DIO7. You can configure
each digital bit for either input or output. All digital I/O lines are pulled up to +5 V with a 47 kΩ resistor
(default). You can request the factory to configure the resistor for pull-down to ground if desired.
Caution! If a digital bit is set up as an alarm, the bit will be configured for output on power-up, and assume
the state defined by the alarm configuration.
When you configure the digital bits for input, you can use the USB-5201 digital I/O terminals to detect the state
of any TTL-level input. Refer to the schematic shown in Figure 4. If you set the switch to the +5 V input, DIO0
reads TRUE (1). If you move the switch to GND, DIO0 reads FALSE (0).
+5V+GND
DIO0
Figure 4. Schematic showing switch detection by digital channel DIO0
Caution! All ground pins on the USB-5201 (pins 9, 19, 28, 38) are common and are isolated from earth
ground. If a connection is made to earth ground when using digital I/O and conductive
thermocouples, the thermocouples are no longer isolated. In this case, thermocouples must not be
connected to any conductive surfaces that may be referenced to earth ground
For general information regarding digital signal connections and digital I/O techniques, refer to the Guide to
Signal Connections (available on our web site at www.mccdaq.com/signals/signals.pdf).
Configuring the DIO channels to generate alarms
The USB-5201 features eight independent temperature alarms. All alarm options are software configurable.
When a digital bit is configured as an alarm, that bit is configured as an output on the next power cycle and
assumes the state defined by the alarm configuration.
Each alarm controls an associated digital I/O channel as an alarm output. The input to each alarm is one of the
temperature input channels. You set up the temperature conditions to activate an alarm, and the output state of
the channel (active high or low) when activated. When an alarm is activated, its associated DIO channel is
driven to the output state specified.
The alarm configurations are stored in non-volatile memory and are loaded on power up. The temperature
alarms function both in data logging mode and while attached to the USB port on a computer.

18
Chapter 4
Functional Details
Thermocouple measurements
A thermocouple consists of two dissimilar metals that are joined together at one end. When the junction of the
metals is heated or cooled, a voltage is produced that correlates to temperature.
The USB-5201 hardware level-shifts the thermocouple’s output voltage into the A/D’s common mode input
range by applying +2.5 V to the thermocouple’s low side at the C#L input. Always connect thermocouple
sensors to the USB-5201 in a floating fashion. Do not attempt to connect the thermocouple low side C#L to
GND or to a ground referencing resistor.
Cold junction compensation (CJC)
When you connect the thermocouple sensor leads to the sensor input channel, the dissimilar metals at the USB-
5201 terminal blocks produce an additional thermocouple junction. This junction creates a small voltage error
term which must be removed from the overall sensor measurement using a cold junction compensation
technique. The measured voltage includes both the thermocouple voltage and the cold junction voltage. To
compensate for the additional cold junction voltage, the USB-5201 subtracts the cold junction voltage from the
thermocouple voltage.
The USB-5201 has two high-resolution temperature sensors that are integrated into the design of the USB-5201.
One sensor is located on the right side of the package, and one sensor is located at the left side. The CJC sensors
measure the average temperature at the terminal blocks so that the cold junction voltage can be calculated. A
software algorithm automatically corrects for the additional thermocouples created at the terminal blocks by
subtracting the calculated cold junction voltage from the analog input's thermocouple voltage measurement.
Increasing the thermocouple length
If you need to increase the length of your thermocouple, use the same type of thermocouple wires to minimize
the error introduced by thermal EMFs.
Data linearization
After the CJC correction is performed on the measurement data, an on-board microcontroller automatically
linearizes the thermocouple measurement data using National Institute of Standards and Technology (NIST)
linearization coefficients for the selected thermocouple type.
The measurement data is then output as a 32-bit floating point value in the configured format (voltage or
temperature).
Open-thermocouple detection (OTD)
The USB-5201 is equipped with an open-thermocouple detection for each analog input channel. With OTD, any
open-circuit or short-circuit condition at the thermocouple sensor is detected by the software. An open channel
is detected by driving the input voltage to a negative value outside the range of any thermocouple output. The
software recognizes this as an invalid reading and flags the appropriate channel. The software continues to
sample all channels when OTD is detected.
Input leakage current
With open-thermocouple detection enabled, 105 nA (max.) of input leakage current is injected into the
thermocouple. This current can cause an error voltage to develop across the lead resistance of the thermocouple
that is indistinguishable from the thermocouple voltage you are measuring. You can estimate this error voltage
with the following formula:
error voltage = resistance of the thermocouple x 105 nA
To reduce the error, reduce the length of the thermocouple to lower its resistance, or lower the AWG of the wire
by using a wire with a larger diameter. With open-thermocouple detection disabled, 30 nA (max.) of input
leakage current is injected into the thermocouple.

USB-5201 User's Guide Functional Details
19
External components
The USB-5201 has the following external components, as shown in Figure 5.
Screw terminals
USB connector
LED
CompactFlash slot with memory card
USB
connector
Screw terminal
Pins 27 to 52
Screw terminal
Pins 1 to 26
LED
CompactFlash
memory card
®
Data logging
button
Figure 5. USB-5201 component locations
Screw terminals
The device's four banks of screw terminals are for connecting temperature sensors and digital I/O lines. These
terminals also provide ground and power output connections. Refer to the "Sensor Connections" chapter for
screw terminal descriptions.
USB connector
When not logging data, connect the USB cable to a USB port on your computer or to an external USB hub that
is connected to your computer. When connected to an active USB bus, the device's USB connector provides
+5 V power and communication. The voltage supplied through the USB connector is system-dependent, and
may be less than 5 V. No external power supply is required.
Due to processing limitations, you cannot log data when the device is attached to an active USB bus. For data
logging operations, connect the device's USB connector to the external power supply.
LED
The LED uses up to 5 mA of current. The function of the LED varies according to whether the USB-5201 is
connected to an active USB port, or when the device is logging data and connected to the external power
supply.
The following table lists the function of the USB-5201 LED when the device is connected to an active USB port
and not logging data.

USB-5201 User's Guide Functional Details
20
LED function when the USB-5201 is connected to an active USB port
LED Illumination
Indication
Steady green
The USB-5201 is connected to a computer or external USB hub.
Blinks continuously
Data is being transferred.
Upon connection, the LED should flash a few times and then remain lit (indicates a
successful installation).
Blinks three times
Initial communication is established between the USB-5201 and the computer.
Off
The USB-5201 is not connected to an active USB port.
Refer to the table below for the function of the USB-5201 LED when the device is connected to the external
supply and is logging data. The function of the LED varies according to the selected logging mode.
LED function when the USB-5201 is logging data
Logging mode
LED Illumination
Indication
Logging off
The LED is off.
The USB-5201 is not logging data,
and/or the device is not powered
Start Logging on
Power Up
The LED turns on when external power is
connected, then blinks each time data is captured.
Blinks when logging data.
Start Logging on
Button
The LED stays off until the data logging button is
pressed and held for approximately 1 second. At
that time, the LED turns on and blinks each time
data is captured.
Blinks when logging data.
Start Logging at
Specified Time
The LED is off –blinks on once per second until
the specified date/time to start logging is reached.
At that time, the LED turns on –blinks off each
time data is captured.
Blinks on once per second until
specified data/time to log data occurs.
Then it turns on and blinks each time
data is captured.
Any logging mode
Blinks rapidly (250 ms period) and continuously.
The memory card is full.
The memory card was removed
during logging. Insert the memory
card again to stop the device
blinking.
CompactFlash®memory card slot
The CompactFlash slot accepts standard memory cards. A 256 MB memory card is shipped with the device. For
extensive data logging, you can insert a higher capacity card of up to 2 GB. You must format the memory card
before logging data for the first time.
Data logging button
The data logging button is used to end a data logging session. The data logging button is also used to start
recording data when the logging mode is set in InstaCal to Start Logging on Button.
To begin recording data, press and hold the button until the LED begins to blink. The first sample is taken
one second after the LED illuminates.
When you first power on the USB-5201, wait at least five seconds before pressing the data logging button.
To achieve rated accuracy, allow the USB-5201 to warm up for 30 minutes before logging data.
To stop recording data, press and hold the button again until the LED is off.
Caution! To prevent loss of data, always use the button to stop logging. Make sure the data is written to the
memory card before you disconnect the device from the power source.
The device caches log data in volatile memory prior to writing to the memory card.
Pressing the data logging button has no effect when the USB-5201 is connected to an active USB port and not
logging data.
External power required for data logging
Due to processing limitations, data logging is not allowed when the USB-5201 is attached to an active USB bus.
The USB-5201 must be connected to the standalone power supply to perform data logging.