Measurement Computing CIO-EXP16 User manual

CIO-EXP16
Analog Multiplexer board
User's Guide
Document Revision 1, January, 2007
© Copyright 2007, Measurement Computing Corporation

3
HM CIO-EXP16.doc
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Trademark and Copyright Information
TracerDAQ, Universal Library, Harsh Environment Warranty, Measurement Computing Corporation, and the Measurement
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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 which, 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.
4

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 CIO-EXP16..................................................................................................................8
Overview: CIO-EXP16 features.........................................................................................................................8
Software features................................................................................................................................................8
Chapter 2
Installing the CIO-EXP16......................................................................................................................9
What comes with your CIO-EXP16 shipment?..................................................................................................9
Hardware .......................................................................................................................................................................... 9
Optional components........................................................................................................................................................ 9
Additional documentation................................................................................................................................................. 9
Unpacking the CIO-EXP16..............................................................................................................................10
Connecting to the A/D board............................................................................................................................10
Signal cable......................................................................................................................................................................10
Cabling.............................................................................................................................................................................11
Configuring the CIO-EXP16............................................................................................................................12
Power source....................................................................................................................................................................13
A/D board type ................................................................................................................................................................15
A/D Channel for EXP Output..........................................................................................................................................15
EXP Gain.........................................................................................................................................................................16
Solder gap switches .........................................................................................................................................................16
Configuring the A/D board...............................................................................................................................17
Single-ended mode ..........................................................................................................................................................17
Range...............................................................................................................................................................................17
Polarity.............................................................................................................................................................................17
Calibrating the CIO-EXP16..............................................................................................................................17
Chapter 3
Functional Details...............................................................................................................................18
CIO-EXP16 inputs............................................................................................................................................18
Connecting to a signal source ..........................................................................................................................................18
Thermocouples .................................................................................................................................................19
Cold junction compensation.............................................................................................................................................20
Open thermocouple detect ...............................................................................................................................................20
Low pass filter .................................................................................................................................................................20
Ground reference .............................................................................................................................................................20
Input impedance...............................................................................................................................................................20
Amplification and thermocouples.....................................................................................................................20
Chapter 4
Programming and Developing Applications....................................................................................22
Programming languages...................................................................................................................................22
Packaged applications programs.......................................................................................................................22
Chapter 5
Specifications......................................................................................................................................23
Analog input.....................................................................................................................................................23
Cold junction compensation.............................................................................................................................23
Analog output...................................................................................................................................................24
5

CIO-EXP16 User's Guide
Digital input......................................................................................................................................................24
Power consumption ..........................................................................................................................................24
Environmental ..................................................................................................................................................24
Main connector and pin out..............................................................................................................................25
6

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 CIO-EXP16 so that you get the most out of its
analog input and digital I/O features.
This user’s guide also refers you to related documents available on our web site, and to technical support
resources.
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
The following electronic documents provide helpful information relevant to the operation of the CIO-EXP16.
MCC's Specifications: CIO-EXP16 (the PDF version of the Specifications chapter in this guide) is available
on our web site at www.mccdaq.com/pdfs/CIO-EXP16.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.
CIO-EXP16 User's Guide (this document) is also available on our web site at
www.mccdaq.com/PDFmanuals/CIO-EXP16.pdf.
7

Chapter 1
Introducing the CIO-EXP16
Overview: CIO-EXP16 features
The CIO-EXP16 is a 16-channel signal conditioning accessory board supported under popular Microsoft®
Windows®operating systems.
The CIO-EXP16 is used to expand the number of analog inputs and the range of amplification of DAS08 and
DAS16 series boards. Using multiple CIO-EXP16 boards, a 16 channel A/D board can be expanded to up to
256 inputs; an 8 channel A/D board can be expanded to up to 128 inputs.
The CIO-EXP16 board has 16 differential inputs that are multiplexed into one single-ended output channel.
Four digital inputs are controlled by the A/D board's digital outputs, and are used to select one of the
multiplexed channels for output. An on-board semiconductor sensor provides a cold junction compensation
(CJC) reference for thermocouple applications.
You select one channel on the A/D board to send the multiplexed analog output to. In addition, you can output
the CJC signal to a second A/D board channel. You can enable an input filter, ground reference, and open
thermocouple detect options for each channel using on-board solder gap switches. You specify the gain of the
multiplexer with an onboard gain switch.
You can power the CIO-EXP16 internally from the A/D board, or externally from the computer's +5 V power
supply connectors.
The CIO-EXP16 board is mounted externally to the PC. It can be placed in the open on a benchtop or in a case.
Software features
For information on the features of InstaCal and the other software included with your CIO-EXP16, 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.
8

Chapter 2
Installing the CIO-EXP16
What comes with your CIO-EXP16 shipment?
The following items are shipped with the CIO-EXP16.
Hardware
CIO-EXP16
Optional components
You can also order the following MCC products to use with your CIO-EXP16.
C37FF-x
C-EXP2DAS16-10 C-PCPOWER-10
BP-POWER
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 CIO-EXP16 and information regarding installation of that software. Please
read this booklet completely before installing any software or hardware.
9

CIO-EXP16 User's Guide Installing the CIO-EXP16
Unpacking the CIO-EXP16
As with any electronic device, you should take care while handling to avoid damage from static
electricity. Before removing the CIO-EXP16 from its packaging, ground yourself using a wrist strap or by
simply touching the computer chassis or other grounded object to eliminate any stored static charge.
If any components are missing or damaged, notify Measurement Computing Corporation immediately by
phone, fax, or e-mail:
Phone: [phone] and follow the instructions for reaching Tech Support.
Fax: [phone] to the attention of Tech Support
Email: [email protected]
Connecting to the A/D board
There are two 37-pin D type connectors on the CIO-EXP16 — P1 and P2. They are wired 1:1. Connector P1 is
labeled NEXT EXP, and is provided to daisy chain additional CIO-EXP16 boards. Use a C37FF-x cable to daisy
chain the CIO-EXP16 boards together. Do not exceed 50 feet in length.
Signals may be connected from the CIO-EXP16 board to the A/D board through one of two types of cables. The
cable used depends upon the type of A/D board you are connecting to. The table below lists the CIO-EXP16
board's connectors and compatible cables.
Board connector, cables, and accessory equipment
Connector type P1 and P2: 37-pin D type connector
Compatible cables with connector P1 C37FF-x (connecting to additional CIO-EXP16 boards)
Compatible cables with connector P2 C37FF-x (connecting to a DAS08 board)
C-EXP2DAS16-10 (connecting to a DAS16 board)
Signal cable
The CIO-EXP16 signal connector is nearly a mirror of the CIO-DAS08 signal cable.
NC / LLGND 19
LLGND / Output 18
Output 9 17
Output 10 16
Output 11 15
Output 12 14
Output 13 13
Output 14 12
Output 15 11
MUX Addr 4 10
MUX Addr 3 9
MUX Addr 2 8
MUX Addr 1 7
NC 6
NC 5
NC 4
NC 3
NC 2
+12V PC Bus 1
37 Output 0
36 Output 1
35 Output 2
34 Output 3
33 Output 4
32 Output 5
31 Output 6
30 Output 7
29 +5V
28 Power GND
27 NC
26 NC
25 NC
24 NC
23 NC
22 NC
21 NC
20 -12V PC Bus
Figure 1. Connector P2/P1
10

CIO-EXP16 User's Guide Installing the CIO-EXP16
Cabling
19
37
1
20
19
37
1
20
The red stripe
identifies pin # 1
Figure 2. C37FF-x cable
Connecting to a DAS08 Series board
Leave the A/D BOARD TYPE jumper in the default DAS08 position. Use a C37FF-x cable to connect to DAS08
series boards.
Connecting to a DAS16 Series A/D Board
Set the A/D BOARD TYPE jumper to the DAS16 position.
Connection to a DAS16 series board requires a special 37-conductor cable (C-EXP2DAS16-10) since the pin
relationship of the CIO-EXP16 and DAS16 signals is not 1:1. Refer to the
table below. C-EXP2DAS16-10 cable pin out
C-EXP2DAS16-10 cable pin out
P1 (MUX) P2
7 23
8 4
9 22
10 3
11 11
12 12
13 13
14 14
15 15
16 16
17 17
18 18
19 19
28 7
29 1
30 30
31 31
32 32
33 33
34 34
35 35
36 36
37 37
N/C Shell Shield
11

CIO-EXP16 User's Guide Installing the CIO-EXP16
Information on signal connections
General information regarding signal connection and configuration is available in the Guide to Signal
Connections (available at www.mccdaq.com/signals/signals.pdf).
Configuring the CIO-EXP16
Before using the CIO-EXP16, there are switches and jumpers to set, and one or more cables to install. Please
turn the PC power OFF before proceeding. The CIO-EXP16 is shipped with the factory-default settings listed in
the following table.
Factory-configured default settings
Jumper/switch Description Default setting
Power source select switch
S3 +5V power switch that sets the power source to
internal or external INT (internal +5V PC power)
A/D BOARD TYPE jumper Selects DAS08 or DAS16 compatibility DAS08
EXP OUTPUT TO DAS
jumper Selects the A/D board channel to connect the multiplexed analog output to. 0
(EXP multiplexed output connects to
channel 0 on the A/D board)
CJC OUTPUT TO DAS
jumper Selects the A/D board channel to connect the CJC output to. 7
(CJC circuit connects to channel 7 on
the A/D board)
GAIN switches
S1 Four DIP switches that set the gain of the
differential amplifier. Gain = 1 (all gain switches OFF)
V, C and G solder bridge
switches (one for each input
channel)
Three 'connect pads' per channel on the etch
side (under side) of the CIO-EXP16 board.
Bridge each pad to configures its associated
input channel as follows:
Bridge the Vpads to enable open
thermocouple detection for the associated
input channel.
Bridge the Cpads to connect a 1 µF
capacitor across the signal high and low
inputs, forming a low-pass filter having a 7
Hz cutoff.
Bridge the Gpads to enable a reference to
ground for the associated input channel.
Open pads (all are not bridged)
12

CIO-EXP16 User's Guide Installing the CIO-EXP16
Figure 3
Figure 3. Switch, jumper, and connector locations
shows the location of the board jumpers, switches, and connectors. The solder bridges are on the under
side of the board, and are not shown in the figure.
A/D Board Type
jumper
External power
connector
P15
Gain
switches
S1
EXP and CJC Output to
DAS channel jumpers
Power
source
switch
S3
Before using the CIO-EXP16, verify that the board is configured with the settings that you want. Review the
following information to change the default configuration of a jumper, switch, or solder gap.
Power source
You can supply +5V DC power to the via the 37-conductor cable from the A/D board in the PC (internal), or via
a separate optional power cable connected directly to the PC power supply (external). The internal method is
adequate for powering up to five CIO-EXP16 boards. Supply external power (connect the C-PCPOWER-10
power cable) when:
More than five CIO-EXP16 boards are used with one A/D board.
The A/D board in use does not supply +5V to its connector
Configure the CIO-EXP16 board’s power source with switch S3 for either internal or external power. Figure 4
shows this switch configured in both positions.
+5V power from the
PC via 37 conductor
signal cable
+5V power from the
PC via 2 conductor
optional
ower cable
C-PCPOWER-10
p
S3+5
EXT INT
Internal power External power
S3+5
EXT INT
Figure 4. Power source-select switch
13

CIO-EXP16 User's Guide Installing the CIO-EXP16
External +5 V PC power connections
You can power the CIO-EXP16 with your computer’s +5V power supply using the optional C-PCPOWER-10
cord. Each end of the cable has a keyed Molex®type connector. To connect to your computer’s power
connectors, do the following:
1.
2.
Turn off power to the computer and remove the cover.
Connect the black cable with the white Molex®type connectors to one of the unused PC expansion power
connectors from the PC power supply. They are keyed, so the cable will plug into the expansion connector
easily when they are aligned (see ).Figure 5
Figure 5. External power cable installation
DC/DC
Signal cable
P2 to CIO-DAS08
analog board
Power cable
J3 to PC Power Supply
Personal Computer
CIO-EXP16
3. Run the power cable out the back of the computer through an expansion slot or other opening and replace
the cover on the computer.
You can alternatively connect the C-PCPOWER-10 to a BP-POWER adaptor to bring PC power out of the
computer. This adaptor provides three standard power connectors mounted on a backplate. Details on this product
are available on our web site at www.mccdaq.com/products/accessories.aspx.
Caution! Be careful not to pinch the cable when you replace the cover—if this cable is cut, the resulting short
circuit can damage the computer.
4.
5.
Connect the other end of the power cord to the connector labeled "OPTIONAL EXTERNAL +5V POWER"
(P15) on the CIO-EXP16. This end is keyed also. Refer to for the location of this connector.Figure 3
Slide the power source select switch (S3) to the EXT position.
14

CIO-EXP16 User's Guide Installing the CIO-EXP16
A/D board type
Use the 4-pin jumper labeled A/D BOARD TYPE to configure the CIO-EXP16 for use with the DAS08 family
of boards or the DAS16 family of boards. Place the jumper in the position for the type of A/D board you are
using with the CIO-EXP16. Fig shows the jumper configured with its default setting of DAS08.ure 6
Figure 6. Board type select jumper
LLGND
P2, pin19
P2, pin 18
DAS16DAS08
A/D Channel for EXP Output
Select a separate A/D channel for each CIO-EXP16 output that you plan to use. Each CIO-EXP16 has two
potential signals — the output of the 16 multiplexed inputs, and the output of the CJC circuit. The output of the
CIO-EXP16 selected channel is an input to the A/D board.
Two rows of 16 jumper pairs located near the 37-pin connectors are labeled with A/D board channel numbers
(see ). These channel numbers designate which of the A/D board's input channels will be connected to
the MUX board’s output(s). Each CIO-EXP16 output, if used, must be exclusively assigned to an A/D channel
using these jumpers. In other words, for all CIO-EXP16 boards attached to an A/D board, only one jumper on
any of the jumper blocks should be assigned to a particular channel.
Figure 7
Figure 7
Figure 7. EXP Channel Select and CJC Select jumper blocks
shows the layout of the jumper blocks on the CIO-EXP16.
01234567 8 9 10 1112 1314 15
EXP OUTPUT TO DA
S
CJC OUTPUT TO DAS
DAS8/16 DAS16 ONLY
These jumpers are for
boards with 16 channels
only, such as the CIO-DAS16
in 16 channel mode.
The CIO-EXP16 has 16 input channels multiplexed into one output. This output is connected to the jumper
block labeled EXP OUTPUT TO DAS. This jumper block determines which analog input channel of the A/D
board in the computer is connected to the output from the CIO-EXP16 board.
The CIO-EXP16 also has a semiconductor temperature sensor on board to measure the temperature of the board
in the region of the screw terminals. The temperature at the screw terminals is needed when thermocouples are
used with the CIO-EXP16. The temperature at the screw terminals is called the Cold Junction temperature, and
is needed to accurately calculate thermocouple temperature. This is known as Cold Junction Compensation.
When a CIO-EXP16 channel is used with a thermocouple, install the CJC OUTPUT TO DAS jumper in the
desired channel location. If you are not using thermocouples, do not install it.
Select the A/D board channel to connect the multiplexed analog output to using the jumpers labeled EXP
OUTPUT TO DAS.
Channels 0-15 are connected by default to A/D board channel 0.
Select the A/D board channel to connect the CJC output to (if required) using the jumpers labeled CJC
OUTPUT TO DAS.
CIO-EXP CJC is connected by default to A/D channel 7.
15

CIO-EXP16 User's Guide Installing the CIO-EXP16
Channel selection for the DAS08 family
The DAS08 family of boards has eight channels of input, so only CIO-EXP16 jumper positions 0-7 are valid.
Many boards in the DAS08 family of boards have single-ended inputs, which is the correct type to connect to a
CIO-EXP16. If the inputs on the board type you are using are differential, they must be converted to single-
ended inputs (refer to the hardware user's manual supplied with your A/D board for more information).
You can connect up to eight banks of 16 CIO-EXP16 inputs to a DAS08 series board, for a total of 128 inputs.
Channel selection for the DAS16 family
The CIO-EXP16 jumper positions 0-7 and 8-15 can be used with the CIO-DAS16. You can connect up to 16
banks of 16 CIO-EXP16 inputs to a DAS16 series board, for a total of 256 inputs.
Most of the DAS16 family of A/D is switch-selectable for either 8 differential or 16 single-ended channels. Set
the switch for 16-channel, single-ended mode.
EXP Gain
The CIO-EXP16 has a bank of four DIP switches that control the gain of the differential amplifier ( ).Figure 8
Figure 8. Gain switch
re 8
4
3
2
1
x500
x200
x100
x10
S1
ON = left
The gain associated with a switch is 'ON' when the switch is to the left, and 'OFF' when the switch is to the
right. The gains are additive, so a total of 16 different gains are possible. The board is shipped with all switches
off (gain =1). The switch shown in Figu is configured for a gain of 700 (500 + 200).
For most thermocouple applications, the gain should be set to at least 100. Refer to the section
on page 20 for data on setting optimum amplifier gains when using thermocouples.
Amplification
and thermocouples
For most other applications, the gain should be set to result in output signal levels as close to ±5V or ±10V
(depending on the range setting on the A/D board) as possible.
Solder gap switches
Each analog input channel on the CIO-EXP16 has three dedicated solder gap switches labeled C, V, and Gon
the circuit side (under side) of the board. Each solder gap switch enables a different thermocouple option. A
typical set of solder gap switches is shown here.
V C G
Figure 9. Solder gap switches (typical per channel)
A solder gap switch has two pads. Turn on each switch by soldering the pads together to close them — this is
called a solder bridge. When closed, or bridged, the pads connect resistors and capacitors to the input signals
and enable the following options:
Open thermocouple detect (V pad) — enables open thermocouple detection to alert you if a
thermocouple breaks. Note that your software program must be designed to recognize when a negative
full-scale condition exists, since the input is pulled to minus full-scale if the thermocouple wire is
broken or disconnected.
Input filter (C pad) — connects a 1 µF capacitor across the signal high and low inputs. This forms a
7 Hz low pass filter that filters out signal noise that is picked up on the thermocouple wire.
16

CIO-EXP16 User's Guide Installing the CIO-EXP16
Input ground reference (G pad) — provides a reference to ground through a 100 k resistor. This
reference prohibits floating thermocouple readings.
You should bridge the C and G pads with solder for each channel that you install a thermocouple. Bridging
these pads reduces the noise present when you take temperature readings, and helps to obtain a more accurate
temperature reading. The C, V, and G pads are all open when the board is shipped.
How to add and remove a solder bridge
To add a solder bridge to a solder gap switch, place a drop of solder on one of the pads and pull the soldering
iron perpendicular to the pads from their center. To remove a solder bridge, slide the soldering iron toward one
pad or the other. Take care not to overheat the solder, or the pads may lift.
Configuring the A/D board
Use InstaCal to change the following configuration options on your DAS08 or DAS16 Series board.
Single-ended mode
DAS08 setup: The input mode of the A/D board must be single-ended to be compatible with the CIO-EXP16
outputs. Some of the boards in the DAS08 series have differential inputs that can be converted to single-ended
inputs. Refer to the user's manual for your hardware for information on conversion to single-ended inputs.
DAS16 setup: The input mode of the A/D board must be single-ended to be compatible with the CIO-EXP16
outputs. Most of the DAS16 series is switch-selectable for either 8 differential or 16 single ended inputs. When
used with the CIO-EXP16, set the switch to 16 channel, single-ended mode.
Range
If the range of your A/D board is switch-selectable, and you are using thermocouples, set the range of the DAS
board to ±5 V, if available, or ±10 V if not. Some software packages base the calculation of temperature on
these ranges only.
If you are not using thermocouples, set the range of the DAS board to accommodate the maximum output
expected from the CIO-EXP16 board.
Polarity
If your A/D board has a UNI / BIP switch for setting the range to either unipolar or bipolar, the preferred setting
is BIP (bipolar).
If the range on your A/D board is fully programmable, the software you use for temperature measurement will
determine the correct range to use.
Calibrating the CIO-EXP16
You should calibrate the CIO-EXP16 after you first connect to a A/D board, if you change the gain setting of
the input amplifier, and at 6 month intervals.
17

Chapter 3
Functional Details
CIO-EXP16 inputs
The CIO-EXP16 inputs are screw terminals which will accept 12-22 AWG wire. Each channel has a screw
terminal for signal high, signal low and ground.
The inputs are differential, which require three connections from the signal source to the CIO-EXP16 — Signal
High, Signal Low, and Signal Ground. A typical connection is shown in .Figure 10
Figure 10. Differential channel connections
Signal High
Signal Low
Low Level Ground
Figure 11
Figure 11. Analog inputs block diagram
shows a block diagram of the board’s 16 analog inputs. One input is selected by the four MUX
address lines that are controlled by the A/D board.
MUX
HI-507
MUX
HI-507
CH15 HIGH
CH15 LOW
CH8 HIGH
CH8 LOW
CH7 HIGH
CH7 LOW
CH0 HIGH
CH0 LOW
GND
GND
Gain
Switch
Gain
Switch
4
EXP out to the
DAS board
Ground
AMP
INA1 10
MUX ADDR
Connecting to a signal source
You can connect analog inputs to the CIO-EXP16 in either a floating differential or differential configuration.
Before connecting to a signal source, measure the voltage between the signal ground at the signal source and
ground at the PC. Do not connect to a signal source if the voltage difference exceeds 10 V, as you will not be
able to obtain a reading.
Caution! DO NOT connect to the signal if the voltage exceeds 30 V — voltages over 30 V will damage the
board and possibly the computer.
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CIO-EXP16 User's Guide Functional Details
Floating differential input
A floating differential input has two wires from the signal source, and a 100 K ground reference resistor
installed at the CIO-EXP16 input. The two signals from the signal source are Signal High (CH#-HI) and Signal
Low (CH#-LO). The reference resistor is connected between the CH#-LO and #-G (Signal Ground) pins.
Use a floating differential hookup when the signal source is floating with respect to ground, such as a battery, 4-
20 mA transmitter or thermocouple, and the lead lengths are long or subject to electromagnetic interference
(EMI) pickup.
A thermocouple is an example of a floating differential signal source. Instead of using an external 100 K
resistor, add a solder bridge between the 'G' pads to enable a ground reference. The floating differential input
will reject up to 10 V of EMI.
Caution! Use a voltmeter to verify that the signal source is floating, or you may damage the CIO-EXP16
and/or your computer.
Differential input
A differential signal uses three wires from the signal source — Signal High (CH#-HI), Signal Low (CH#-LO)
and Signal Ground (#-G).
With a differential configuration, you can connect the CIO-EXP16 to a signal source with a ground that is
different from the PC ground, but with less than 10 V difference, and still make a true measurement of the
signal between CH# HI and CH# LO. An example of this is a laboratory instrument with its own wall plug,
where there are sometimes differences in wall grounds between outlets.
Information on signal connections
For general information about signal connection and configuration, refer to the Guide to Signal Connections on
our web site at www.mccdaq.com/signals/signals.pdf.
Thermocouples
A thermocouple is made of two dissimilar wires that react electrically when in contact with each other. The
reaction produces a voltage which is dependent on the temperature at the point where the two metals touch.
There is a reaction at every point where dissimilar metals (the thermocouple wire) touch, including the screw
terminal where the thermocouple wire is connected to the CIO-EXP16 board.
To process thermocouple signals, the CIO-EXP16 provides cold junction compensation (CJC), open
thermocouple detect (OTD) and stable amplification for accurate temperature measurements.
Figure 12
Figure 12. Typical thermocouple connection
shows a thermocouple connected to one channel of the CIO-EXP16. The thermocouple has a positive
and a negative lead. If you're not sure which is the positive lead and which is the negative lead, make a test
hookup and use a match to heat the thermocouple. If the temperature reading goes down, switch the leads.
C = Filter capacitor, pad open. V = Open TC Detect, pad open. G = Reference to ground, pad open.
Pads are located on the circuit side.All pads must be closed when thermocouples are used.
Thermocouple
negative lead
Thermocouple
positive lead High
Low
Ground
Ground
Low
High
-15 V
3.9M
10K
10K
100K
1F
µ
C
V
G
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CIO-EXP16 User's Guide Functional Details
Cold junction compensation
The CIO-EXP16 has a semiconductor temperature sensor to measure the temperature of the board around the
screw terminals—this is called the cold junction temperature. This sensor provides a stable, accurate and linear
output which is temperature-dependent. The cold junction temperature is required to accurately calculate the
thermocouple temperature. This is known as cold junction compensation (CJC). You can map the sensor output
to one of the A/D board's analog inputs using the CJC output to DAS jumper block.
The CJC reference is required for accurate temperature readings
The CJC temperature reference is universally used by software to compensate for the voltage induced at the
cold junction (the area around the screw terminals). If you don't supply a CJC reference your temperature
readings may be inaccurate.
Open thermocouple detect
You enable open thermocouple detect (OTD) by closing the channel’s associated 'V' pad with a solder bridge.
OTD applies a full-scale negative voltage to the high side of the thermocouple signal. If a thermocouple opens,
the OTD voltage drives the signal on that channel to negative full-scale.
Design your software program to recognize when a negative full-scale condition exists, since the input is pulled
to negative full-scale if the thermocouple wire is broken or disconnected. Most software is set up to alarm for an
open thermocouple when a temperature falls to negative full-scale.
The CIO-EXP16 will accurately measure thermocouples when the 'V' pad is open, but without OTD protection
enabled.
Low pass filter
A low pass filter is implemented by closing the 'C' pad. When bridged, a 1 µF capacitor is connected across the
signal’s high and low inputs, forming a low-pass filter. The bandwidth of this filter is 7 Hz. Signals changing at
rates greater than 7 times per second are damped. The low pass filter helps to reject noise picked up along the
thermocouple wire. Since temperature measurement is generally a ‘low frequency’ application, the filter does
not affect the temperature measurement.
The CIO-EXP16 will accurately measure thermocouples when the 'C' pad is open, but the measurements may
fluctuate due to noise present on the thermocouple wire.
Ground reference
The CIO-EXP16 inputs are fully differential, which help reject noise on thermocouple wires. Close the ‘G’ pad
thermocouples to work properly. The 'G' pad provides a reference from ground to the analog low input via a 100
K resistor. When closed, enough current passes through the resistor to provide a reference to ground. The
analog high and low inputs are still able to float within the common mode range.
Input impedance
When you leave the V and G pads open, the input impedance is greater than 100 M ohms. When you short the
V and G pads, the input impedance is 100 k ohms.
Amplification and thermocouples
The voltage from a thermocouple is very low and must be amplified to take advantage of the A/D board’s full
resolution. Use the GAIN switch to set the amplification of the CIO-EXP16 board's 16 analog inputs (see
on page 16). Figure 8
The following table lists the theoretical amplifier output voltage at maximum temperature for each gain. In most
cases, the range on the A/D board is set to ±5 V. The maximum voltage for some thermocouple/gain
combinations can exceed the maximum A/D input range (typically 5 V), or even the maximum output voltage
of the CIO-EXP16 board (±10 V).
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