USB-TC-AI
Thermocouple and Voltage Measurement

User's Guide

Document Revision 4A
March 2013
© Copyright 2013

Trademark and Copyright Information
Measurement Computing Corporation, InstaCal, Universal Library, and the Measurement Computing logo areeither 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.
© 2013 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.
NoticeMeasurement 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 ininjury. 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 ofpeople.

HM USB-TC-AI.docx

2

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-TC-AI ................................................................................................................... 6
Functional block diagram ................................................................................................................................... 6
Connecting a USB-TC-AI to your computer is easy .......................................................................................... 7
Chapter 2

Installing the USB-TC-AI....................................................................................................................... 8
What comes with your shipment? ....................................................................................................................... 8
Hardware .......................................................................................................................................................................... 8
Documentation .................................................................................................................................................................. 8

Unpacking........................................................................................................................................................... 8
Installing the software ........................................................................................................................................ 8
Installing the hardware ....................................................................................................................................... 8
Configuring the hardware ................................................................................................................................... 9
Calibrating the hardware..................................................................................................................................... 9
Chapter 3

Signal I/O Connections .......................................................................................................................10
Screw terminal pinout ....................................................................................................................................... 10
Voltage input ...................................................................................................................................................................10
Thermocouple input .........................................................................................................................................................11
CJC sensor .......................................................................................................................................................................11
Digital I/O ........................................................................................................................................................................11
Counter input ...................................................................................................................................................................11
Power output ....................................................................................................................................................................11
Ground .............................................................................................................................................................................11

Thermocouple connections ............................................................................................................................... 11
Wiring configuration........................................................................................................................................................11

Digital I/O connections ..................................................................................................................................... 12
Chapter 4

Functional Details ...............................................................................................................................13
Thermocouple measurements ........................................................................................................................... 13
Cold junction compensation (CJC) ..................................................................................................................................13
Data linearization .............................................................................................................................................................13
Open-thermocouple detection (OTD) ..............................................................................................................................13

External components ........................................................................................................................................ 14
Screw terminals................................................................................................................................................................14
USB connector .................................................................................................................................................................14
LEDs ................................................................................................................................................................................14

Power ................................................................................................................................................................ 14
Chapter 5

Specifications ......................................................................................................................................15
Analog input ..................................................................................................................................................... 15
Channel configurations ..................................................................................................................................... 16
Compatible sensors: T0x toT3x .......................................................................................................................................163

USB-TC-AI User's Guide

Accuracy ........................................................................................................................................................... 17
Thermocouple measurement accuracy: T0x to T3x .........................................................................................................17
Absolute accuracy: V0x-V3x ...........................................................................................................................................18
Settling time: V0x-V3x ....................................................................................................................................................18

Analog input calibration ................................................................................................................................... 19
Throughput rate ................................................................................................................................................ 19
Digital I/O ......................................................................................................................................................... 19
Temperature alarms .......................................................................................................................................... 20Counter ............................................................................................................................................................. 20
Memory ............................................................................................................................................................ 20
Microcontroller ................................................................................................................................................. 21
USB +5V voltage ............................................................................................................................................. 21
Power ................................................................................................................................................................ 21
USB specifications ........................................................................................................................................... 21
Environmental .................................................................................................................................................. 21
Mechanical ....................................................................................................................................................... 22
Screw terminal connector ................................................................................................................................. 22
Declaration of Conformity ..................................................................................................................23

4

Preface

About this User’s Guide
What you will learn from this user's guideThis user's guide describes the Measurement Computing USB-TC-AI data acquisition device and lists device
specifications.

Conventions in this user's guide
For more information
Text presented in a box signifies additional information related to the subject matter.
Caution! Shaded caution statements present information to help you avoid injuring yourself and others,
damaging your hardware, or losing your data.
bold text

Bold text is used for the names of objects on a screen, such as buttons, text boxes, and check boxes.

italic text

Italic text is used for the names of manuals and help topic titles, and to emphasize a word or phrase.

Where to find more information
Additional information about USB-TC-AI hardware is available on our website at www.mccdaq.com. You canalso contact Measurement Computing Corporation with specific questions.


Knowledgebase: kb.mccdaq.com
Phone: 508-946-5100 and follow the instructions for reaching Tech Support
Fax: 508-946-9500 to the attention of Tech Support
Email: techsupport@mccdaq.com

5Chapter 1

Introducing the USB-TC-AI
The USB-TC-AI is a USB 2.0 full-speed, thermocouple input module that is supported under popular
Microsoft® Windows® operating systems. The USB-TC-AI is fully compatible with both USB 1.1 and USB 2.0
ports.
The USB-TC-AI provides eight analog input channels that are configured as four differential temperature inputs
and four differential or single-ended voltage inputs. A 24-bit analog-to-digital (A/D) converter is provided foreach pair of analog inputs. 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 aresoftware programmable for input or output.
The temperature channels are software programmable for different thermocouple types. You can takemeasurements from type J, K, R, S, T, N, E, and B thermocouples.
The voltage input range is software programmable for ±10 V, ±5 V, ±2.5 V, ±1.25 V.
The USB-TC-AI provides a integrated cold junction compensation (CJC) sensor for thermocouple
measurements. An open thermocouple detection feature lets you detect a broken thermocouple.
An on-board microprocessor automatically linearizes the measurement data.
The USB-TC-AI is a standalone plug-and-play module which draws power from the USB cable. No external
power supply is required. All configurable options are software programmable.
The USB-TC-AI is fully software calibrated.

Functional block diagram
USB-TC-AI functions are illustrated in the block diagram shown here.

Figure 1. USB-TC-AI functional block diagram6

USB-TC-AI User's Guide

Introducing the USB-TC-AI

Connecting a USB-TC-AI to your computer is easy
Installing a data acquisition device has never been easier.









The USB-TC-AI relies upon the Microsoft Human Interface Device (HID) class drivers. The HID classdrivers 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 foryour USB-TC-AI. No third-party device driver is required.
The USB-TC-AI is plug-and-play. There are no jumpers to position, DIP switches to set, or interrupts toconfigure.
You can connect the USB-TC-AI before or after you install the software, and without powering down yourcomputer first. When you connect an HID to your system, your computer automatically detects it andconfigures the necessary software. You can connect and power multiple HID peripherals to your systemusing a USB hub.
You can connect your system to various devices using a standard USB cable. The USB connector replaces
the serial and parallel port connectors with one standardized plug and port combination.
You do not need a separate power supply module. The USB automatically delivers the electrical power
required by each peripheral connected to your system.
Data can flow two ways between a computer and peripheral over USB connections.

7

Chapter 2

Installing the USB-TC-AI
What comes with your shipment?
The following items are shipped with the USB-TC-AI:

Hardware

USB-TC-AI
USB cable (2 meter length)

Documentation
In addition to this hardware user's guide, you should also receive the Quick Start Guide. This booklet provides
an overview of the MCC DAQ software you received with the device, and includes information about installingthe software. Please read this booklet completely before installing any software or hardware.

UnpackingAs with any electronic device, you should take care while handling to avoid damage from static
electricity. Before removing the USB-TC-AI from its packaging, ground yourself using a wrist strap or bysimply touching the computer chassis or other grounded object to eliminate any stored static charge.
If any components are missing or damaged, contact us immediately using one of the following methods:

Knowledgebase: kb.mccdaq.com
Phone: 508-946-5100 and follow the instructions for reaching Tech Support
Fax: 508-946-9500 to the attention of Tech Support
Email: techsupport@mccdaq.com

For international customers, contact your local distributor. Refer to the International Distributors section on our
website at www.mccdaq.com/International.

Installing the software
Refer to the Quick Start Guide for instructions on installing the software on the MCC DAQ CD. This booklet isavailable in PDF at www.mccdaq.com/PDFmanuals/DAQ-Software-Quick-Start.pdf.

Installing the hardware
To connect the USB-TC-AI 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 powerand communication to the USB-TC-AI.
When you connect the USB-TC-AI for the first time, a notification message opens as the USB-TC-AI isdetected. When this message closes, the installation is complete. The upper LED (Activity) blinks when initiallyconnected and then stays on. The lower LED (USB) turns on to indicate that communication is establishedbetween the device and computer.
If the LED turns off
If the LED is on but then turns off, the computer has lost communication with the USB-TC-AI. 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.

8

USB-TC-AI User's Guide

Installing the USB-TC-AI

Configuring the hardware
All hardware configuration options on the USB-TC-AI are programmable with software. Use InstaCal to set thethermocouple type for each channel pair.
Use InstaCal to set the thermocouple type for each for each pair of temperature channels, and the range andinput configuration of each voltage channel. Any channel you don’t intend to use should be left disabled.
Configuration options are stored on the USB-TC-AI 's isolated microcontroller in EEPROM, which is nonvolatile memory on the USB-TC-AI module. Configuration options are loaded on power up. The factory default
configuration is Type J thermocouple.
Default configuration
The factory default configuration for the voltage inputs is Disabled. The Disabled mode disconnects the analog
inputs from the terminal blocks and internally grounds all of the A/D inputs.
Warm up
Allow the USB-TC-AI to warm up for 30 minutes after powering up before taking measurements. This warm up
time minimizes thermal drift and achieves the specified rated accuracy of measurements.

Calibrating the hardware
The USB-TC-AI is fully calibrated via InstaCal. Allow the USB-TC-AI to operate for at least 30 minutes before
calibrating. This warm up time minimizes thermal drift and achieves the specified rated accuracy ofmeasurements.

9

Chapter 3

Signal I/O Connections
Screw terminal pinout
The USB-TC-AI 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 screw terminals 10 and 11 is the integrated CJC sensor
used for thermocouple measurements. Signals are identified in Figure 2.

Figure 2. USB-TC-AI screw terminal pin numbers

Use 16 AWG to 30 AWG wire for your signal connections.
Tighten screw terminal connections
When making connections to the screw terminals, be sure to tighten the screw until tight. Simply touching the
top of the screw terminal is not sufficient to make a proper connection.

Voltage input
You can connect up to four voltage inputs to the voltage channels ( V0H/V0L to V3H/V3L). The input range issoftware programmable for ±10 V, ±5 V, ±2.5 V, or ±1.25 V. Each voltage channel is software configurable fordifferential or single-ended mode.
When connecting differential inputs to floating input sources, you must provide a DC return path from eachdifferential input to ground. One way to do this is to connect a resistor from one side of each of the differential
inputs to GND. A value of approximately 100 kΩ can be used for most applications.
Caution! All ground pins on the USB-TC-AI (pins 9, 19, 22, 27, 30, 33, 36, 39, 49) are common and are
isolated from earth ground. If a connection is made to earth ground when using digital I/O andconductive 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.

10USB-TC-AI User's Guide

Signal I/O Connections

Thermocouple input
You can connect up to four thermocouples to the differential sensor inputs ( T0H/T0L to T3H/T3L). The device
supports type J, K, R, S, T, N, E, and B thermocouples. You can mix thermocouple types.
Thermocouple selection
The thermocouple type you select will depend on your application needs. Review the temperature ranges andaccuracies of each type to determine which is best suited for your application.

CJC sensor
The USB-TC-AI has one built-in high-resolution temperature sensor. The CJC sensor measures the ambient
temperature at the terminal block so that the cold junction voltage can be calculated.

Digital I/O
You can connect up to eight digital I/O lines to the screw terminals labeled DIO0 to DIO7. Each terminal issoftware configurable for input or output.

Counter input
The CTR terminal is the input to the 32-bit event counter. The internal counter increments when the TTL leveltransitions from low to high. The counter can count events at frequencies of up to 1 MHz.
Caution! All ground pins on the USB-TC-AI (pins 9, 19, 22, 27, 30, 33, 36, 39, 49) are common and are
isolated from earth ground. If a connection is made to earth ground when using digital I/O andconductive 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.

Power output
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 or you may damage
the USB-TC-AI and possibly the computer.

GroundThe 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.

Thermocouple connections
A thermocouple consists of two dissimilar metals that are joined together at one end. When the junction of themetals is heated or cooled, a voltage is produced that correlates to temperature.
The USB-TC-AI 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 thermocouple input which automatically detects anopen or broken thermocouple.
Use InstaCal to select the thermocouple type (J, K, R, S, T, N, E, and B) on one or more sensor input channels
to connect the thermocouple.

Wiring configuration
Connect the thermocouple to the USB-TC-AI using a differential configuration, as shown in Figure 3.

11

USB-TC-AI User's Guide

Signal I/O Connections

Figure 3. Typical thermocouple connection

Connect thermocouples to the USB-TC-AI such that they are floating with respect to GND (pins 9, 19, 28, 38).
The USB-TC-AI GND pins are isolated from earth ground, so connecting thermocouple sensors to voltages
referenced to earth ground is permissible 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, we recommend the use of 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-TC-AI is powered on, and ±40 VDC when the USB-TC-AI 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.

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 +5V with a 47 kΩ resistor(default). You can request the factory to configure the resistor for pull-down to ground if desired.
When you configure the digital bits for input, you can use the USB-TC-AI digital I/O terminals to detect thestate of a TTL-compatible device. Refer to the schematic shown in Figure 4. If you set the switch to the +5V
input, DIO0 reads TRUE (1). If you move the switch to GND, DIO0 reads FALSE (0).

Figure 4. Schematic showing switch detection by digital channel DIO0

All ground pins on the USB-TC-AI (pins 9, 19, 22, 27, 30, 33, 36, 39, 49) are isolated from earth ground. If aconnection 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 groundFor 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).

12

Chapter 4

Functional Details
Thermocouple measurements
A thermocouple consists of two dissimilar metals that are joined together at one end. When the junction of themetals is heated or cooled, a voltage is produced that correlates to temperature.
The USB-TC-AI 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-TC-AI 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 USBTC-AI terminal blocks produce two additional thermocouple junctions. 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-TC-AI subtracts the cold junction voltage fromthe thermocouple voltage.
The USB-TC-AI has one high-resolution temperature sensor integrated into the design. The CJC sensor
measures the average temperature at the terminal block so that the cold junction voltage can be calculated. A
software algorithm automatically corrects for the additional thermocouples created at the terminal blocks bysubtracting 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 automaticallylinearizes 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 ortemperature).

Open-thermocouple detection (OTD)
The USB-TC-AI is equipped with 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 tosample all channels when OTD is detected.

13

USB-TC-AI User's Guide

Functional Details

External components
The USB-TC-AI has the following external components, as shown in Figure 5.

1
2

Screw terminal pins 1 to 26
Screw terminal pins 27 to 52

3
4

LEDs: Activity (top) and Power (bottom)
USB connector

Figure 5.External component locations

Screw terminals
The screw terminals provide connections for thermocouples, voltage input, digital I/O, ground and power
output. Refer to the "Signal I/O ConnectionsError! Reference source not found." chapter beginning on page
10 for screw terminal descriptions.

USB connector
The USB connector provides +5V power and communication. No external power supply is required.

LEDs
USB-TC-AI has two LEDs – Activity and Power.


The Activity LED (top) blinks when data is transferred.
The Power LED (bottom) turns on when the device is receiving power from the USB cable .

Power
The two +5V terminals are isolated (500 VDC) from the USB +5V.
Caution! Each +5V terminal is an output. Do not connect to an external power supply or you may damage
the USB-TC-AI and possibly the computer.

14

Chapter 5

Specifications
Typical for 25 °C unless otherwise specified.
All specifications apply to all temperature and voltage input channels unless otherwise specified.
Specifications in italic text are guaranteed by design.

Analog input
Table 1. Generic analog input specifications
Parameter

Conditions

Specification

A/D converter typeT0x-T3x, V0x-V3xNumber of channels

Voltage input V0x-V3xAD42_321
Dual 24-bit Sigma-Delta
4 differential, 4 single-ended

Temperature input T0x-T3x
Input isolation
Channel configuration

T0x-T3xV0x-V3x

Analog input modes

Power up and reset state

Single-ended

Differential

Input ranges

Absolute max input voltage

Thermocouple
T0x-T3x
VoltageV0x to V3x
T0x to T3x relative to GND
V0x to V3x relative to GND

Input impedance

T0x to T3x
V0x to V3x

Input leakage current

Input bandwidth(–3 dB)
Maximum working voltage(signal + common mode)

T0x to T3x, with open
thermocouple detect disabled.
T0x-T3x, with open
thermocouple detect enabled.
V0x to V3x
T0x to T3x
V0x to V3xV0x to V3x15

4 differential
500 VDC minimum between field wiring and USB
interfaceTemperature input.
Software programmable to match sensor type
Voltage input
Factory default configuration is Disabled mode.
Once configured, each channel reverts to the mode
previously set by the user.
Vx_H inputs are connected directly to their screw
terminal pins.
Vx_L inputs are disconnected from their screw
terminal pins and internally connected to GND.
Vx_H and Vx_L inputs are connected directly totheir screw terminal pins.
Tx_H and Tx_L inputs are connected directly to theirscrew terminal pins.
±0.080 V±10 V, ±5 V, ±2.5 V, ±1.25 V
software selectable±25 V max (power on)±40 V max (power off)
±25 V max (power on)±15 V max (power off)
5 GΩ (power on)
1MΩ (power off)
10 GΩ (power on)
2.49 kΩ (power off)
30 nA max
105 nA max±1.5 nA typ, ±25 nA max
50 Hz
3 kHz
±10.25 V max

USB-TC-AI User's Guide

Specifications

Parameter

Conditions

Specification

Common mode rejection ratio

T0x to T3x, fIN = 60 Hz
V0x to V3x, fIN = 60 Hz, all
input ranges

100 dB
83 dB

ADC resolution
ADC No missing codes
Input couplingWarm-up time
Open thermocouple detect

CJC sensor accuracy

T0x to T3x

T0x to T3x, 15 °C to 35 °C
T0x to T3x, 0°C to 70 °C

24 bits
24 bitsDC
30 minutes min
Automatically enabled when the channel pair isconfigured for thermocouple sensor.
The max open detection time is 3 seconds.
±0.25 °C typ,±0.5 °C max–1.0 to +0.75 °C max

Channel configurations
Table 2. Channel configuration specifications
ChannelCategory

Conditions

Specification

T0x to T3x

Disabled

All temperature input channels are disconnected from screw
terminals and internally connected to GND.

See Note 4T0x to T3x

Thermocouple
Note 1Disabled

V0x to V3xV0x to V3xV0x to V3x

4 differential channels
All voltage input channels are disconnected from screw
terminals and internally connected to GND.

Differential
Note 2Single-ended

See Note 4
4 differential channels
4 single-ended
channels

Note 1: Internally, the USB-TC-AI has four, dual-channel, fully differential A/Ds providing a total of eight

input channels.
Note 2: When connecting differential inputs to floating input sources, you must provide a DC return path fromeach differential input to ground. To do this, connect a resistor from each of the differential inputs to
GND. A value of approximately 1Meg ohm can be used for most applications.
Note 3: Channel configuration information is stored in the EEPROM of the isolated microcontroller by thefirmware whenever any item is modified. Modification is performed by commands issued over USB
from an external application, and the configuration is made non-volatile through the use of the
EEPROM.
Note 4: The factory default configuration is Disabled. The Disabled mode will disconnect the temperature andvoltage inputs from the terminal blocks and internally connect ground (GND) to all of the A/D inputs.

Compatible sensors: T0x toT3xTable 3. Compatible sensor type specifications
Parameter

Conditions (°C)

Thermocouple

J: –210 to 1200
K: –270 to 1372
R: –50 to 1768
S: –50 to 1768
T: –270 to 400
N: –270 to 1300
E: –270 to 1000
B: 0 to 182016

USB-TC-AI User's Guide

Specifications

Accuracy
Thermocouple measurement accuracy: T0x to T3x
Table 4. Thermocouple accuracy specifications, including CJC measurement error. All specifications are (±)
SensorType

Sensor temperature
range (°C)

Accuracy error
maximum (°C)

Accuracy error
Typical (°C)

Tempco(°C/°C)

J

–210
0
1200
–210
0
1372
–50
250
1768
–50
250
1768
250
700
1820
–200
0
1000
–200
0
400
–200
0
1300

2.028
0.835
0.783
2.137
0.842
0.931
1.225
0.554
0.480
1.301
0.549
0.400
2.193
0.822
0.469
1.976
0.954
0.653
2.082
0.870
0.568
2.197
0.848
0.653

0.707
0.278
0.288
0.762
0.280
0.389
0.435
0.195
0.157
0.458
0.190
0.134
2.185
0.819
0.468
0.684
0.321
0.240
0.744
0.290
0.208
0.760
0.283
0.245

0.031

K

S

R

B

E

T

N

0.035

0.021

0.019

0.001

0.030

0.035

0.028

Note 5: Thermocouple measurement accuracy specifications include polynomial linearization, cold-junction

compensation and system noise. These specs are for one year, or 3000 operating hours, whichevercomes first, and for operation of the USB-TC-AI between 15 °C and 35 °C. There is a CJC sensor on
the temperature sensor input side of the module. The accuracy listed above assumes the screw
terminals are at the same temperature as the CJC sensor. Errors shown do not include inherent
thermocouple error. Contact your thermocouple supplier for details on the actual thermocouple
accuracy error.
Note 6: Thermocouples must be connected to the USB-TC-AI such that they are floating with respect to GND.
The USB-TC-AI GND pins are isolated from earth ground. You can connect thermocouple sensors tovoltages referenced to earth ground as long as the isolation between the GND pins and earth ground ismaintained.
Note 7: When thermocouples are attached to conductive surfaces, the voltage differential between multiple
thermocouples must remain within ±1.4 V. For best results, we recommend using insulated or
ungrounded thermocouples when possible.

17

USB-TC-AI User's Guide

Specifications

Absolute accuracy: V0x-V3xTable 5. Calibrated absolute accuracy specifications
Range

Absolute Accuracy
(mV)

±10 V
±5 V
±2.5 V±1.25 V

±2.779±1.398±0.707±0.362

Note 8: When connecting differential inputs to floating input sources, the user must provide a ground return

path from each differential input to ground. To do this, simply connect a resistor from each of thedifferential inputs to GND. A value of approximately 1Meg ohm can be used for most applications.
Note 9: All ground pins are common and are isolated from earth ground. If a connection is made to earth
ground when using both voltage inputs and conductive thermocouples, the thermocouples are nolonger isolated. In this case, thermocouples must not be connected to any conductive surfaces that may
be referenced to earth ground
Note 10:
Unused voltage inputs should not be left floating. These inputs should be placed in the Disabledmode or connected to GND.
Table 6. Accuracy components. All values are (±)
Range

Gain error(% of reading)

Offset error(µV)

INL error(% of range)

Gain Temperature
Coefficient(ppm/°C)

Offset Temperature
Coefficient(µV/°C)±10 V±5 V±2.5 V±1.25 V

0.02460.02460.02460.0246

16.75
16.75
16.75
16.75

0.00150.00150.00150.0015

3.68
3.68
3.68
3.68

0.42
0.42
0.42
0.42

Table 7. Noise performance specifications
Range

Peak to peak noise(µV)

RMS noise(µVrms)

Noise-Free resolution(bits)±10 V±5 V±2.5 V±1.25 V

41.13
30.85
17.14
11.14

6.23
4.67
2.60
1.69

19.09
18.51
18.36
17.98

Table 7 summarizes the noise performance for the USB-TC-AI. Noise distribution is determined by gathering
1000 samples with inputs tied to ground at the user connector. Samples are gathered at the maximum specified
sample rate of 2 S/s.

Settling time: V0x-V3xTable 8. Settling time specifications
Range

Accuracy±0.0004% (seconds)

±10 V
±5 V
±2.5 V±1.25 V

15.0
0.40
0.40
0.40

Settling time is defined as the time required for a channel to settle within a specified accuracy in response to afull-scale (FS) step input.
18USB-TC-AI User's Guide

Specifications

Analog input calibration
Table 9. Analog input calibration specifications
Parameter

Specification

Recommended warm-up time
Calibration
Calibration interval
Calibration reference

30 minutes min
Firmware calibration
1 year
+10.000 V, ±5 mV max. Actual measured values stored in EEPROM
Tempco: 5 ppm/°C max
Long term stability: 30 ppm/1000 h

Throughput rate
Table 10. Throughput rate specifications
Number of Input Channels

Maximum throughput

1
2
3
4
5
6
7
8

2 S/s
2 S/s on each channel, 4 S/s total
2 S/s on each channel, 6 S/s total
2 S/s on each channel, 8 S/s total
2 S/s on each channel, 10 S/s total
2 S/s on each channel, 12 S/s total
2 S/s on each channel, 14 S/s total
2 S/s on each channel, 16 S/s total

Note 11:

The analog inputs are configured to run continuously. Each channel is sampled twice per second.
The maximum latency between when a sample is acquired and the voltage/temperature data isprovided by the USB unit is approximately 0.4 seconds.

Digital I/O
Table 11. Digital input/output specifications
Parameter

Specification

Digital type
Number of I/O
Configuration

5V CMOS
8 (DIO0 through DIO7)
Independently configured for input or output.
Power on reset is input mode.
All pins pulled up to +5 V via 47 K resistors (default). Contact MCC factory for pulldown to ground (GND) capability.
 Digital input: 50 port reads or single bit reads per second typ
 Digital output: 100 port writes or single bit writes per second typ
2.0 V min, 5.5 V absolute max.
0.8 V max, –0.5 V absolute min
0.7 V max

Pull-up/pull-down
configuration
Digital I/O transfer rate
(software paced)
Input high voltage
Input low voltage
Output low voltage(IOL = 2.5 mA max)
Output high voltage(IOH = -2.5 mA max)
Note 12:

3.8 V minAll ground pins on the USB-TC-AI (pins 9, 19, 22, 27, 30, 33, 36, 39, 49) are common and are
isolated from earth ground. If a connection is made to earth ground when using digital I/O andconductive thermocouples, the thermocouples are no longer isolated. In this case, thermocouples mustnot be connected to any conductive surfaces that may be referenced to earth ground.

19

USB-TC-AI User's Guide

Specifications

Temperature alarms
Table 12. Temperature alarm specifications
Parameter

Specification

Number of alarms
Alarm functionality

8 (one per digital I/O line)
Each alarm controls its associated digital I/O line as an alarm output. The input to each
alarm may be any of the analog temperature input channels. When an alarm is enabled, its
associated I/O line is set to output (after the device is reset) and driven to the appropriate
state determined by the alarm options and input temperature. The alarm configurations are
stored in non-volatile memory and are loaded at power on. Alarms will function both indata logging mode and while attached to USB.
 Alarm when input temperature > T1
 Alarm when input temperature > T1, reset alarm when input temperature goes below T2
 Alarm when input temperature < T1
 Alarm when input temperature < T1, reset alarm when input temperature goes above T2
 Alarm when input temperature is < T1 or > T2
Note: T1 and T2 may be independently set for each alarm.
 Disabled, digital I/O line may be used for normal operation
 Enabled, active high output (digital I/O line goes high when alarm conditions met) Enabled, active low output (digital I/O line goes low when alarm conditions met)
1 second

Alarm input modes

Alarm output modes

Alarm update rate

CounterTable 13. CTR I/O specifications
Parameter

Specification

Pin name
Number of channels
Resolution
Counter type
Input type
Input source
Counter read/writes rates(software paced)CTR
132-bits
Event counter
TTL, rising edge triggered
CTR screw terminal
Counter read: system dependent, 33 to 1000 reads per second.
Counter write: system dependent, 33 to 1000 reads per second.
20 mV to 100 mV±1.0 µA typ
1 MHz max
500 nS min
500 ns min
4.0 V min, 5.5 V absolute max
1.0 V max, –0.5 V absolute min

Schmidt trigger hysteresis
Input leakage current
Input frequency
High pulse width
Low pulse width
Input high voltage
Input low voltage
Note 13:

All ground pins are common and are isolated from earth ground. If a connection is made to earth
ground with both the counter (CTR) and conductive thermocouples, the thermocouples are no longer
isolated. In this case, thermocouples must not be connected to any conductive surfaces that may bereferenced to earth ground.

MemoryTable 14. Memory specifications
Parameter

Specification

EEPROM

1,024 bytes isolated micro reserved for sensor configuration
256 bytes USB micro for external application use

20

USB-TC-AI User's Guide

Specifications

Microcontroller
Table 15. Microcontroller specifications
Parameter

Specification

Type

Two high-performance 8-bit RISC microcontrollers

USB +5V voltage
Table 16. USB +5V voltage specifications
Parameter

Specification

USB +5V (VBUS) input
voltage range

4.75 V min to 5.25 V max

Power
Table 17. Power specifications
Parameter

Conditions

Specification

Supply current
Supply current(Note 14)User +5V output voltage range(terminal block pin 21)
User +5V output current(terminal block pin 21)
Isolation

USB enumeration
Continuous mode with all inputs configured for
Disabled mode.

<100 mA
270 mA typ

Note 14:

4.9 V min to 5.1 V max
Bus-powered and connected to a self-powered hub.
(Note 14)5 mA max

Measurement system to PC

500 VDC min

This is the total current requirement for the USB-TC-AI which includes up to 10 mA for the
status LED.

USB specifications
Table 18. USB specifications
Parameter

Specification

USB device type
Device compatibility
Device power capability
USB cable type

USB 2.0 (full-speed)
USB 1.1, USB 2.0
Self-powered
A-B cable, UL type AWM 2725 or equivalent. (min 24 AWG VBUS/GND,
min 28 AWG D+/D–)
3 meters max

USB cable length

Environmental
Table 19. Environmental specifications
Parameter

Specification

Operating temperature range
Storage temperature range
Humidity

0 °C to 55 °C max–40 °C to 85 °C max
0% to 90% non-condensing max

21USB-TC-AI User's Guide

Specifications

Mechanical
Table 20. Mechanical specifications
Parameter

Specification

Dimensions (L × W × H)User connection length

128.52 x 88.39 × 35.56 mm (5.06 × 3.48 × 1.43 ft)
3 m (9.84 ft) max

Screw terminal connector
Table 21. Screw terminal connector specifications
Parameter

Specification

Connector type
Wire gauge range

Screw terminal
16 AWG to 30 AWG
Table 22. Screw terminal pinout

Pin
1
2
3
4
5
6
7
8
9
10

Signal Name
RSVD
NC
T0H
T0L
NC
RSVD
T1H
T1L
GND
RSVD

Pin Description
Reserved, Do Not Use
No connection
T0 sensor input (+)
T0 sensor input (–)
No connection
Reserved, Do Not Use
T1 sensor input (+)
T1 sensor input (–)
GroundReserved, Do Not Use

Pin
27
28
29
30
31
32
33
34
35
36

Signal Name
GND
V3L
V3H
GND
V2L
V2H
GND
V1L
V1H
GND

Pin Description
GroundV3 voltage input (–)
V3 voltage input (+)
GroundV2 voltage input (–)
V2 voltage input (+)
Ground
V1 voltage input (–)
V1 voltage input (+)

Reserved, Do Not Use
No connection
T2 sensor input (+)
T2 sensor input (–)
No connection
Reserved, Do Not Use
T3 sensor input (+)
T3 sensor input (–)
GroundReserved, Do Not Use+5V output
GroundNo connection
No connection
No connection
No connection

37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52

V0L
V0H
GND
CTR
DIO7
DIO6
DIO5
DIO4
DIO3
DIO2
DIO1
DIO0
GND
NC
NC
NC

V0 voltage input (–)
V0 voltage input (+)
GroundCounter Input
DIO channel 7
DIO channel 6
DIO channel 5
DIO channel 4
DIO channel 3
DIO channel 2
DIO channel 1
DIO channel 0
GroundNo connection
No connection
No connection

CJC sensor
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26

RSVD
NC
T2H
T2L
NC
RSVD
T3H
T3L
GND
RSVD
+5V
GND
NC
NC
NC
NC

22

Declaration of Conformity
Manufacturer:
Address:

Category:

Measurement Computing Corporation
10 Commerce Way
Suite 1008
Norton, MA 02766
USAElectrical equipment for measurement, control and laboratory use.

Measurement Computing Corporation declares under sole responsibility that the product

USB-TC-AI
EU EMC Directive 89/336/EEC: Electromagnetic Compatibility, EN 61326 (1997) Amendment 1 (1998)
Emissions: Group 1, Class A
EN 55011 (1990)/CISPR 11: Radiated and Conducted emissions.

Immunity: EN61326, Annex AIEC 61000-4-2 (1995): Electrostatic Discharge immunity, Criteria C.
IEC 61000-4-3 (1995): Radiated Electromagnetic Field immunity Criteria A.
IEC 61000-4-8 (1994): Power frequency magnetic field immunity Criteria A.

Declaration of Conformity based on tests conducted by Chomerics Test Services, Woburn, MA 01801, USA in
July, 2007. Test records are outlined in Chomerics Test Report #EMI4833.07.
We hereby declare that the equipment specified conforms to the above Directives and Standards.

Carl Haapaoja, Director of Quality Assurance

Measurement Computing Corporation
10 Commerce Way
Suite 1008
Norton, Massachusetts 02766(508) 946-5100
Fax: (508) 946-9500
E-mail: info@mccdaq.com
www.mccdaq.com