Omega OM-WLS-TC, OM-WLS-TEMP User guide

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regulations that apply. OMEGA is constantly pursuing certification of its products to the European New
Approach Directives. OMEGA will add the CE mark to every appropriate device upon certification.

The information contained in this document is believed to be correct, but OMEGA accepts no liability for any
errors it contains, and reserves the right to alter specifications without notice.
WARNING: These products are not designed for use in, and should not be used for, human applications.

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 OM-WLS Series .......................................................................................................... 6

OM-WLS-TC and OM-WLS-TEMP features .................................................................................................... 6

Sensor support .................................................................................................................................................................. 6

Remote wireless operation ................................................................................................................................................ 6

OM-WLS-IFC features ....................................................................................................................................... 7

Functional block diagrams .................................................................................................................................. 7

Software features ................................................................................................................................................ 8

Chapter 2

Installing a OM-WLS Series Device ..................................................................................................... 9

What comes with your shipment? ....................................................................................................................... 9

OM-WLS-TC/ OM-WLS-TEMP Hardware ..................................................................................................................... 9

OM-WLS-IFC Hardware .................................................................................................................................................. 9

Documentation .................................................................................................................................................................. 9

Unpacking ........................................................................................................................................................... 9

Installing the software ........................................................................................................................................ 9

Installing the hardware ..................................................................................................................................... 10

Configuring OM-WLS Series hardware ........................................................................................................... 10

Temperature sensors ........................................................................................................................................................10

Network parameters (remote operation) ..........................................................................................................................11

Connecting the external power supply for remote operation ............................................................................ 12

Calibrating OM-WLS Series hardware ............................................................................................................. 12

Warm up time ................................................................................................................................................... 12

Chapter 3

Sensor Connections ........................................................................................................................... 13

Screw terminal pinout (OM-WLS-TEMP and OM-WLS-TC) ......................................................................... 13

Sensor input terminals......................................................................................................................................................14

Current excitation output terminals (OM-WLS-TEMP) ..................................................................................................14

Four-wire, two sensor common (OM-WLS-TEMP) ........................................................................................................14

Two sensor common (OM-WLS-TEMP) ........................................................................................................................14

CJC sensors ......................................................................................................................................................................14

Digital I/O (DIO0 to DIO7) .............................................................................................................................................14

Ground .............................................................................................................................................................................14

Power output (+5V) .........................................................................................................................................................14

Thermocouple connections (OM-WLS-TC and OM-WLS-TEMP) ................................................................. 15

Wiring configuration ........................................................................................................................................................15

RTD and thermistor connections (OM-WLS-TEMP) ...................................................................................... 15

Two-wire configuration ...................................................................................................................................................16

Three-wire configuration .................................................................................................................................................17

Four-wire configuration ...................................................................................................................................................17

Semiconductor sensor measurements (OM-WLS-TEMP) ............................................................................... 18

Wiring configuration ........................................................................................................................................................18

Digital I/O connections (OM-WLS-TC and OM-WLS-TEMP) ....................................................................... 19

Configuring the DIO channels to generate alarms ...........................................................................................................19

3

OM-WLS Series User's Guide

Chapter 4

Functional Details ............................................................................................................................... 20

Thermocouple measurements ........................................................................................................................... 20

Cold junction compensation (CJC) ..................................................................................................................................20

Data linearization .............................................................................................................................................................20

Open-thermocouple detection ..........................................................................................................................................20

RTD and thermistor measurements .................................................................................................................. 21

Data linearization .............................................................................................................................................................21

AC power supply .............................................................................................................................................. 21

External components ........................................................................................................................................ 21

OM-WLS-TC and OM-WLS-TEMP ...............................................................................................................................21

OM-WLS-IFC ..................................................................................................................................................................23

Chapter 5

Specifications ...................................................................................................................................... 24

Analog input (OM-WLS-TEMP and OM-WLS-TC only) ............................................................................... 24

Channel configurations (OM-WLS-TEMP and OM-WLS-TC only) ............................................................... 25

Compatible sensors (OM-WLS-TEMP and OM-WLS-TC only) ..................................................................... 25

Accuracy (OM-WLS-TEMP and OM-WLS-TC only) ..................................................................................... 26

Thermocouple measurement accuracy .............................................................................................................................26

Semiconductor sensor measurement accuracy (OM-WLS-TEMP only) ..........................................................................26

RTD measurement accuracy (OM-WLS-TEMP only) .....................................................................................................27

Thermistor measurement accuracy (OM-WLS-TEMP only) ...........................................................................................27

Throughput rate to PC (USB or wireless) (OM-WLS-TEMP and OM-WLS-TC only) ................................... 28

Digital input/output (OM-WLS-TEMP and OM-WLS-TC only) ..................................................................... 29

Temperature alarms (OM-WLS-TEMP and OM-WLS-TC only) .................................................................... 29

Memory ............................................................................................................................................................ 30

Microcontroller ................................................................................................................................................. 30

Wireless communications ................................................................................................................................. 30

USB +5V voltage ............................................................................................................................................. 30

Power ................................................................................................................................................................ 31

USB specifications ........................................................................................................................................... 31

Current excitation outputs (Ix+) (OM-WLS-TEMP only) ................................................................................ 32

Environmental .................................................................................................................................................. 32

Mechanical ....................................................................................................................................................... 32

LED/button configuration ................................................................................................................................. 33

OM-WLS-TEMP and OM-WLS-TC ...............................................................................................................................33

OM-WLS-IFC ..................................................................................................................................................................34

Screw terminal connector type and pinout (OM-WLS-TEMP and OM-WLS-TC only) .................................. 35

4

About this User’s Guide

What you will learn from this user’s guide

This user's guide describes the Omega Engineering OM-WLS Series data acquisition devices and lists device
specifications.

Conventions in this user's guide

For more information about …

Text presented in a box signifies additional information and helpful hints related to the subject matter you are
reading.

Caution! Shaded caution statements present information to help you avoid injuring yourself and others,

damaging your hardware, or losing your data.

bold text Bold text is used for the names of objects on 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.

Preface

Where to find more information

Additional information about OM-WLS Series hardware is available on our website at www.omega.com. You
can also contact Omega Engineering by phone, fax, or email with specific questions.

 Phone: [phone]
 Fax: [phone]
 Email: [email protected]

5

Chapter 1

Introducing the OM-WLS Series

The OM-WLS Series includes the following devices:

 OM-WLS-TC
 OM-WLS-TEMP
 OM-WLS-IFC

OM-WLS Series hardware are USB 2.0 full-speed devices temperature measurement devices supported under
popular Microsoft® Windows® operating systems. The OM-WLS Series is compatible with both USB 1.1 and
USB 2.0 ports, although the speed of the module maybe limited when using USB 1.1 ports.

The OM-WLS-TC and OM-WLS-TEMP can be operated as local devices connected to a computer, or as
remote devices. Remote operation requires the OM-WLS-IFC USB-to-wireless interface device and an external
power supply (included).

OM-WLS-TC and OM-WLS-TEMP features

The OM-WLS-TC and OM-WLS-TEMP hardware provide the following features:

 Eight differential temperature input channels

A 24-bit analog-to-digital (A/D) converter is provided for each pair of analog inputs. Each pair of inputs
constitutes a channel pair.

 Eight digital I/O channels

The DIO channels are independently configurable for input or output, and can monitor TTL-level inputs,
communicate with external devices, and generate alarms

 Two integrated cold junction compensation (CJC) sensors

Each CJC sensor is dedicated to two channel pairs.

 Open thermocouple detection (OTD)
 Temperature alarms
 Onboard microprocessor automatically linearizes the measurement data according to the sensor category

Sensor support

The OM-WLS-TC supports thermocouple sensors. The OM-WLS-TEMP supports thermocouples, resistance
temperature detectors (RTD), thermistors, and semiconductor sensors.

The sensor category is software-selectable for each channel pair. With the OM-WLS-TEMP, each channel pair
can connect to a different category of sensor. The sensor category between the channels that constitute a
channel pair cannot be mixed. However, thermocouple types within a channel pair can be mixed.

Remote wireless operation

Before operating remotely, you first connect the device to the computer's USB port and configure the network
parameters required to establish a wireless link with the OM-WLS-IFC interface device. All configurable
options are programmable with InstaCal.

During remote operation, the OM-WLS-TC and OM-WLS-TEMP communicate with the computer through the
OM-WLS-IFC device connected to the computer's USB port. External power is required for remote operation.

For more information on setting up network parameters, refer to "Network parameters (remote operation)" on
page 11.

6

OM-WLS Series User's Guide Introducing the OM-WLS Series

OM-WLS-IFC features

The OM-WLS-IFC device operates as the interface between a computer and one or more remote OM-WLS
Series devices. Remote devices can be located up to 150 feet (50 meters) indoors, or up to ½ mile (750 m)
outdoors from the OM-WLS-IFC.

You configure the network parameters required for communication with remote devices. All configurable
options are programmable with InstaCal. Only devices with the same parameter settings can communicate with
each other. Once you configure the OM-WLS-IFC to communicate with remote devices, you can connect it to
different computers without having to configure the network parameters.

Device LEDs indicate the status of communication over the wireless link. An LED bar graph shows the fade
margin of signals received by the OM-WLS-IFC.

The OM-WLS-IFC draws power through the USB cable, and no external power is required.

For more information on setting up network parameters, refer to "Network parameters (remote operation)" on
page 11.

Functional block diagrams

OM-WLS-TC and OM-WLS-TEMP device functions are illustrated in the block diagram shown here.

Figure 1. OM-WLS-TC and OM-WLS-TEMP functional block diagram

7

OM-WLS Series User's Guide Introducing the OM-WLS Series

OM-WLS-IFC device functions are illustrated in the block diagram shown here.

Figure 2. OM-WLS-IFC functional block diagram

Software features

For information on the features of InstaCal and the other software included with your OM-WLS Series
hardware, refer to the OMB-DAQ-2400, OM-USB, OM-WEB, and OM-WLS Series Data Acquisition Software
User’s Guide that shipped with the device.

8

Installing an OM-WLS Series Device

What comes with your shipment?

The following items are shipped with OM-WLS Series hardware:

OM-WLS-TC/ OM-WLS-TEMP Hardware

 OM-WLS-TC or OM-WLS-TEMP
 USB cable
 AC-to-USB power adapter (required for wireless operation)

OM-WLS-IFC Hardware

 OM-WLS-IFC
 USB cable

Documentation

The following documentation ships with the OM-WLS Series hardware:

 OMB-DAQ-2400, OM-USB, OM-WEB, and OM-WLS Series Data Acquisition Software User’s Guide

This booklet provides an overview of the software you received with the device.

 OM-WLS Series Wireless Setup Quick Start

This document provides a procedure to perform wireless temperature measurement out-of-the-box.
Detailed information is provided in this user’s guide.

Chapter 2

Unpacking

As with any electronic device, you should take care while handling to avoid damage from static
electricity. Before removing the device from its packaging, ground yourself using a wrist strap or by simply
touching the computer chassis or other grounded object to eliminate any stored static charge.

If any components are missing or damaged, notify Omega Engineering immediately by phone, fax, or e-mail.

 Phone: [phone]
 Fax: [phone]
 Email: [e-mail]

Installing the software

Refer to the OMB-DAQ-2400, OM-USB, OM-WEB, and OM-WLS Series Data Acquisition Software User’s
Guide for instructions on installing the software on the Software for OMB-DAQ-2400, OM-USB, OM-WEB, and
OM-WLS Series Data Acquisition Modules CD. This booklet is available in PDF at

http://www.omega.com/manuals/manualpdf/M4803.pdf.

9

OM-WLS Series User's Guide Installing an OM-WLS Series Device

Installing the hardware

Install the software before you install your hardware

The driver needed to run your board is installed with the software. Therefore, you need to install the software
before you install your hardware.

To connect OM-WLS Series hardware to your system, perform the following steps:

1. Turn your computer on and connect the USB cable to a USB port on your computer or to an external USB

hub connected to your computer. The USB cable provides power and communication to the OM-WLS
Series hardware.

Always connect an external hub to its power supply

If you are using a hybrid hub (one that can operate in either self-powered or bus-powered mode), always
connect it to its external power supply.

If you use a hub of this type without connecting to external power, communication errors may occur that could
result in corrupt configuration information on your wireless device. You can restore the factory default
configuration settings with InstaCal.

When you connect OM-WLS Series hardware for the first time, a Found New Hardware dialog opens
when the operating system detects the device. The dialog closes after the device is installed

After your system detects new hardware, the Found New Hardware Wizard opens and prompts you for the
location of the software required to run the new hardware.

2. Keep the default selection "Install the software automatically" and then click Next.

The wizard locates and installs the software on your computer for the OM-WLS Series hardware. A dialog
appears when the wizard completes the installation.

3. Click Finish to exit the Found New Hardware Wizard.

After installing the OM-WLS-TC or OM-WLS-TEMP, the Command LED blinks on the device, and then turns
on to indicate that communication is established between the device and the computer. Refer to Figure 13 on
page 21 for the locations of this LED.

If the Command LED turns off (OM-WLS-TC and OM-WLS-TEMP)

If the Command LED is on but then turns off, the computer has lost communication with the OM-WLS-TC or
OM-WLS-TEMP device. If the device is connected to the computer's USB port, disconnect the USB cable from
the computer and then reconnect it. This should restore communication, and the LED should turn on.

If the Command LED turns off when you are operating the OM-WLS-TC or OM-WLS-TEMP remotely
through the wireless interface, disconnect the USB cable from the USB power adapter, and then reconnect it.
This should restore communication, and the Command and Wireless Power LEDs should turn on.

After installing the OM-WLS-IFC, the Power and USB Activity LEDs blink, and then the Power LED turns on
to indicate that communication is established between the device and the computer, and that the device is
receiving power. Refer to Figure 14 on page 23 for the locations of these LEDs.

Configuring OM-WLS Series hardware

Before using OM-WLS Series devices, configure the temperature sensors and network parameters for remote
wireless communication. All hardware configuration options are programmable with InstaCal. Configuration
options are stored on the device in non-volatile memory in EEPROM, and are loaded on power up.

Temperature sensors

Use InstaCal to set the sensor type for each channel pair of an OM-WLS-TEMP or OM-WLS-TC. The
configurable options of the OM-WLS-TEMP dynamically update according to the selected sensor category.

You can configure sensor settings when the device is connected locally to the computer through the USB port,
or when the device is operated remotely through the wireless interface.

10

OM-WLS Series User's Guide Installing an OM-WLS Series Device

RF
Channel

Transmission
Frequency (GHz)

RF
Channel

Transmission
Frequency (GHz)

12

2.410

18

2.440

13

2.415

19

2.445

14

2.420

20

2.450

15

2.425

21

2.455

16

2.430

22

2.460

17

2.435

23

2.465

The factory default sensor configuration is Disabled. The Disabled mode disconnects the analog inputs from the
terminal blocks and internally grounds all of the A/D inputs. This mode also disables each of the current
excitation sources.

Network parameters (remote operation)

The following network parameter options are programmable with InstaCal.

 Identifier: Text that identifies the device (optional).
 PAN (hex): The personal area network (PAN) ID assigned to the device.

The PAN value is a number used to identify the interface device with which you want to communicate. The
OM-WLS Series devices can only communicate with a device whose PAN is set to the same value.

Most users do not need to change the default value assigned to the device. However, you may want to
assign a different PAN ID in the following situations:

o You have multiple OM-WLS Series devices, and do not want to allow communication between all of

them. Set the PAN ID to the same value on each device that you want to communicate.

o If other OM-WLS Series devices are operating in the vicinity, you can avoid accidental changes to

your device settings by changing the default PAN value.

 CH: The radio frequency (RF) channel number assigned to the device.

The channel number is used to transmit and receive data over the wireless link. You may want to change
the channel number in InstaCal when another OM-WLS Series device is already transmitting on that
channel, or when noise is present on the channel.

The table below lists each available channel and its corresponding transmission frequency.

 AES Key: Value used to encrypt data (optional).

AES encryption is disabled by default. Unless you suspect that there are other users of OM-WLS Series
devices in the area, there should be no need to enable encryption. However, if you suspect that there are
other OM-WLS Series devices in the area and you need to secure the devices from being accessed by other
users, enable AES encryption.

Enabling encryption does NOT secure the device from access through a local USB connection. A remote
device configured for encryption can be connected locally through the USB port to access other remote
OM-WLS Series devices with the same settings; you may need to physically secure the remote devices to
prevent tampering of the of device's network settings.

Set the PAN ID, RF channel, and AES key to the same value for each device that you want to
communicate

Only devices with matching parameter settings for PAN, CH, and AES Key (if set) can communicate with each
other.
For information on setting up the network parameters for your OM-WLS Series device, refer to the "OM-WLS
Series" section of the "Temperature Input Boards" chapter in the Universal Library User's Guide.

After configuring the network parameters, disconnect the OM-WLS Series device from the computer, and move
the device to its remote location. The OM-WLS-TC and OM-WLS-TEMP can be located up to 150 feet
(50 meters) indoors, or up to ½ mile (750 m) outdoors from the OM-WLS-IFC.

Restoring factory default settings

You can restore the factory default configuration settings with InstaCal.

11

OM-WLS Series User's Guide Installing an OM-WLS Series Device

Connecting the external power supply for remote operation

Connect the USB cable to the AC-to-USB power adapter when you are operating an OM-WLS-TC or
OM-WLS-TEMP device remotely through the OM-WLS-IFC interface. The Command and Wireless Power
LEDs turn on approximately five seconds after you connect the AC power adapter.

Caution! To satisfy FCC RF exposure requirements for mobile transmitting devices, maintain a separation

distance of 20 cm (0.66 feet) or more between the antenna of this device and personnel during
device operation. To ensure compliance, operation at closer than this distance is not
recommended. The antenna used for this transmitter must not be co-located in conjunction with
any other antenna or transmitter.

Calibrating OM-WLS Series hardware

The OM-WLS-TC and OM-WLS-TEMP support field calibration with InstaCal. Allow a 30-minute warm up
before calibrating. InstaCal prompts you to run its calibration utility when you change the sensor category
configured for the device. If you don't change the sensor category, the normal calibration interval is once per
year. You can calibrate the OM-WLS-TC and OM-WLS-TEMP whether connected locally or remotely.

You can restore the factory default configuration settings with InstaCal.

Warm up time

Allow OM-WLS Series hardware to warm up for 30 minutes before taking measurements. This warm up time
minimizes thermal drift and achieves the specified rated accuracy of measurements.

For RTD or thermistor measurements, this warm-up time is also required to stabilize the internal current
reference.

12

Sensor type

OM-WLS-TC

OM-WLS-TEMP

Thermocouple – types J, K, R, S, T, N, E, and B
4

4

Resistance temperature detectors (RTDs) – two-, three-, or
four-wire measurement modes of 100 Ω platinum RTDs.

4

Thermistors – two-, three-, or four-wire measurement
modes

4
Semiconductor temperature sensors – LM36 or equivalent

4

Chapter 3

Sensor Connections

The temperature sensor types supported by the OM-WLS-TEMP and OM-WLS-TC are shown here:

The type of sensor you select depends on your application needs. Review the temperature ranges and accuracies
of each sensor type to determine which is best suited for your application.

Screw terminal pinout (OM-WLS-TEMP and OM-WLS-TC)

The OM-WLS-TEMP and OM-WLS-TC have four banks of screw terminals. Between each bank of screw
terminals are two integrated CJC sensors used for thermocouple measurements. Signal locations are identified
in Figure 3.

1

OM-WLS-TEMP only. These pins are labeled RSVD (reserved for future use) on the OM-WLS-TC.

2

OM-WLS-TEMP only. "NC" (no connection) on the OM-WLS-TC.

Do not connect anything to pins labeled "NC".

Figure 3. OM-WLS-TEMP and OM-WLS-TC pinout

13

OM-WLS Series User's Guide Sensor 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.

Sensor input terminals

You can connect up to eight temperature sensors to the differential sensor inputs (C0H/C0L to C7H/C7L).
Supported sensor categories include thermocouples, RTDs, thermistors, or semiconductor sensors.

The sensor category is software-selectable for each channel pair. With the OM-WLS-TEMP, each channel pair
can connect to a different category of sensor. Do not mix sensor categories within channel pairs. However,
thermocouple types within a channel pair can be mixed.

Do not connect two different sensor categories to the same channel pair

Each channel pair has a dedicated 24-bit A/D converter. Each channel pair can monitor one sensor category. To
monitor a sensor from a different category, connect the sensor to a different channel pair of input terminals.

Current excitation output terminals (OM-WLS-TEMP)

The OM-WLS-TEMP has four dedicated pairs of current excitation output terminals (±I1 to ±I4). These
terminals have a built-in precision current source to provide excitation for the resistive sensors used for RTD
and thermistor measurements.

Current excitation terminals are dedicated to one pair of sensor input channels:

 I1+ and I1– are the current excitation source for channel 0 and channel 1
 I2+ and I2– are the current excitation source for channel 2 and channel 3
 I3+ and I3– are the current excitation source for channel 4 and channel 5
 I4+ and I4– are the current excitation source for channel 6 and channel 7

Four-wire, two sensor common (OM-WLS-TEMP)

Terminals 4W01 to 4W67 are used as the common connection for four-wire configurations with two RTD or
thermistor sensors.

Two sensor common (OM-WLS-TEMP)

Terminals IC01 to IC67 are used as the common connection for two-wire configurations with two RTD or
thermistor sensors.

CJC sensors

The OM-WLS-TEMP and OM-WLS-TC have two built in high-resolution temperature sensors for
thermocouple measurements. These sensors measure the ambient temperature at the terminal block so that the
cold junction voltage can be calculated.

Digital I/O (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.

Ground

The six ground terminals (GND) provide a common ground for the input channels and DIO bits, and are isolated
(500 VDC) from the USB GND.

Power output (+5V)

The two +5V output terminals are isolated (500 VDC) from the USB +5V.

14

OM-WLS Series User's Guide Sensor Connections

Thermocouple connections (OM-WLS-TC and OM-WLS-TEMP)

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 OM-WLS-TC and OM-WLS-TEMP make 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, T, N, E, and B) and one or more sensor input channels
to connect the thermocouple.

Wiring configuration

Connect thermocouples using a differential configuration, as shown in Figure 4.

Figure 4. Typical thermocouple connection

Connect thermocouples so that they float with respect to GND (pins 9, 19, 28, 38). The GND pins are isolated
from earth ground, so you can connect thermocouple sensors to voltages referenced to earth ground as long as
you maintain the isolation between the GND pins (9, 19, 28, 38) and earth ground.

When you attach thermocouples 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
OM-WLS-TEMP or OM-WLS-TC is powered on, and ±40 VDC when the OM-WLS-TEMP or OM-WLS-TC
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.

RTD and thermistor connections (OM-WLS-TEMP)

A resistance temperature detector (RTD) measures temperature by correlating the resistance of the RTD
element with temperature. A thermistor is a thermally-sensitive resistor that is similar to an RTD in that its
resistance changes with temperature. Thermistors show a large change in resistance that is proportional to a
small change in temperature. The main difference between RTD and thermistor measurements is the method
used to linearize the sensor data.

RTDs and thermistors are resistive devices that need an excitation current to produce a voltage drop that can be
measured differentially across the sensor. The OM-WLS-TEMP has four built-in current excitation sources (±I1
to ±I4) for measuring resistive type sensors. Each current excitation source is dedicated to one channel pair.

The OM-WLS-TEMP can make two, three, and four-wire measurements of RTDs (100 Ω platinum type) and
thermistors.

15

OM-WLS Series User's Guide Sensor Connections

Use InstaCal to select the sensor type and the wiring configuration. Once the resistance value is calculated, the
value is linearized in order to convert it to a temperature value. A 32-bit floating point value in either
temperature or resistance is returned by software.

 In RTD mode, the OM-WLS-TEMP cannot measure resistance values greater than 660 Ω. This 660 Ω

resistance limit includes the total resistance across the current excitation (±Ix) pins, which is the sum of the
RTD resistance and the lead resistances.

 In thermistor mode, the OM-WLS-TEMP cannot measure resistance values greater than 180 kΩ. This

180 kΩ resistance limit includes the total resistance across the current excitation (±Ix) pins, which is the
sum of the thermistor resistance and the lead resistance.

Two-wire configuration

The easiest way to connect an RTD sensor or thermistor to the OM-WLS-TEMP is with a two-wire
configuration, since it requires the fewest connections to the sensor. With this method, the two wires that
provide the RTD sensor with its excitation current also measure the voltage across the sensor.

Since RTDs exhibit a low nominal resistance, the lead wire resistance can affect measurement accuracy. For
example, connecting lead wires that have a resistance of 1 Ω (0.5 Ω each lead) to a 100 Ω platinum RTD results
in a 1% measurement error.

With a two-wire configuration, you can connect either one sensor per channel pair, or two sensors per channel
pair.

Two-wire, single-sensor

A two-wire, single-sensor measurement configuration is shown in Figure 5.

Figure 5. Two-wire, single RTD or thermistor sensor measurement configuration

When you select a two-wire, single-sensor configuration with InstaCal, connections to C#H and C#L are made
internally.

Two-wire, two sensor

A two-wire, two-sensor measurement configuration is shown in Figure 6.

Figure 6. Two-wire, two RTD or thermistor sensors measurement configuration

When you select a two-wire, two-sensor configuration with InstaCal, connections to C#H (first sensor) and
C#H/C#L (second sensor) are made internally.

When configured for two-wire mode, connect both sensors to obtain proper measurements.

16

OM-WLS Series User's Guide Sensor Connections

Three-wire configuration

A three-wire configuration compensates for lead-wire resistance by using a single-voltage sense connection.
With a three-wire configuration, you can connect only one sensor per channel pair. A three-wire measurement
configuration is shown in Figure 7.

Figure 7. Three-wire RTD or thermistor sensor measurement configuration

When you select a three-wire sensor configuration with InstaCal, the OM-WLS-TEMP measures the lead
resistance on the first channel (C#H/C#L) and measures the sensor itself using the second channel (C#H/C#L).
This configuration compensates for any lead-wire resistance and temperature change in lead-wire resistance.
Connections to C#H for the first channel and C#H/C#L of the second channel are made internally.

For accurate three wire compensation, the individual lead resistances connected to the ±I# pins must be of equal
resistance value.

Four-wire configuration

With a four-wire configuration, connect two sets of sense/excitation wires at each end of the RTD or thermistor
sensor. This configuration completely compensates for any lead-wire resistance and temperature change in lead­wire resistance.

Connect your sensor with a four-wire configuration when your application requires very high accuracy
measurements. Examples of a four-wire single-sensor measurement configuration are shown in Figure 8 and
Figure 9.

You can configure the OM-WLS-TEMP with either a single sensor per channel or two sensors per channel pair.

Four-wire, single-sensor

A four-wire, single-sensor connected to the first channel of a channel pair is shown in Figure 8.

Figure 8. Four-wire, single RTD or thermistor sensor measurement configuration

17

OM-WLS Series User's Guide Sensor Connections

A four-wire, single-sensor connected to the second channel of a channel pair is shown in Figure 9.

Figure 9. Four-wire, single RTD or thermistor sensor measurement configuration

Four-wire, two-sensor

A four-wire, two-sensor measurement configuration is shown in Figure 10.

Figure 10. Four-wire, two RTD or thermistor sensors measurement configuration

When configured for four-wire, two sensor mode, both sensors must be connected to obtain proper
measurements.

Semiconductor sensor measurements (OM-WLS-TEMP)

Semiconductor sensors are suitable over a range of approximately –40 C to 125 C, where an accuracy of
±2 C is adequate. The temperature measurement range of a semiconductor sensor is small when compared to
thermocouples and RTDs. However, semiconductor sensors are accurate, inexpensive, and easily interface with
other electronics for display and control.

The OM-WLS-TEMP makes high-resolution measurements of semiconductor sensors, such as the LM36 or
equivalent, and returns a 32-bit floating point value in either a voltage or temperature format. Use InstaCal to
select the sensor type (TMP36 or equivalent), and the sensor input channel that connects to the sensor.

Wiring configuration

You can connect a TMP36 (or equivalent) semiconductor sensor to the OM-WLS-TEMP using a single-ended
configuration, as shown in Figure 11. The device also provides +5V and GND pins for powering the sensor.

Figure 11. Semiconductor sensor measurement configuration

18

OM-WLS Series User's Guide Sensor Connections

The Universal Library outputs the measurement data as a 32-bit floating point value in either voltage or
temperature.

Digital I/O connections (OM-WLS-TC and OM-WLS-TEMP)

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 digital I/O terminals to detect the state of any
TTL-level input. Refer to the schematic shown in Figure 12. 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 12. Schematic showing switch detection by digital channel DIO0

Caution! All ground pins 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 OMB-DAQ-
2400, OM-USB, OM-WEB, and OM-WLS Series General Guide to Signal Connections (available on our web
site at www.omega.com/manuals/manualpdf/M4830.pdf).

Configuring the DIO channels to generate alarms

The OM-WLS-TC and OM-WLS-TEMP feature eight independent temperature alarms. All alarm options are
software configurable. Remote alarm configuration is supported.

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 also 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 in wireless operations and while attached to the USB port on a computer.

You can configure alarm settings when you connect the device locally to the computer through the USB port, or
when operating remotely through the wireless interface. All configurable options are selectable with software.

19

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 OM-WLS-TC and OM-WLS-TEMP hardware level-shifts the thermocouple’s output voltage into the ADC
common mode input range by applying +2.5 V to the thermocouple’s low side at the C#L input. Always
connect thermocouple sensors 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 device
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 device subtracts the cold junction voltage from the thermocouple
voltage.

The OM-WLS-TC and OM-WLS-TEMP have two high-resolution CJC temperature sensors. 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 onboard 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

Open-thermocouple detection (OTD) is automatically enabled for each analog input channel when a channel
pair is configured for thermocouple sensor. The maximum open detection time is 3 seconds.

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, a maximum of 105 nA 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 OTD disabled, a maximum of 30 nA of input leakage current is
injected into the thermocouple.

20

OM-WLS Series User's Guide Functional Details

1

Screw terminal pins 1 to 26

4

LED Test button

7

Transmit LED

2

Screw terminal pins 27 to 52

5

Received Signal Strength (RSS) LEDs

8

Wireless Power LED

3

Command LED

6

Receive LED

9

USB connector

RTD and thermistor measurements

RTDs and thermistors are resistive devices that require an excitation current to produce a voltage drop that can
be measured differentially across the sensor. The device measures the sensor resistance by forcing a known
excitation current through the sensor and then measuring (differentially) the voltage across the sensor to
determine its resistance.

After the voltage measurement is made, the resistance of the RTD is calculated using Ohms law – the sensor
resistance is calculated by dividing the measured voltage by the current excitation level (±Ix) source. The value
of the ±Ix source is stored in local memory.

Once the resistance value is calculated, the value is linearized in order to convert it to a temperature value. The
measurement is returned by software as a 32-bit floating point value in a voltage, resistance or temperature
format.

Data linearization

An onboard microcontroller automatically performs linearization on RTD and thermistor measurements.

 RTD measurements are linearized using a Callendar-Van Dusen coefficients algorithm (you select DIN,

SAMA, or ITS-90).

 Thermistor measurements are linearized using a Steinhart-Hart linearization algorithm (you supply the

coefficients from the sensor manufacturer's data sheet).

AC power supply

 The external power supply is an AC-to-USB 2.5 W supply that is used to power the OM-WLS-TC and

OM-WLS-TEMP during remote wireless operations (Omega part number OM-USB-5200-ADAPTOR.)

External components

OM-WLS-TC and OM-WLS-TEMP

The OM-WLS-TC and OM-WLS-TEMP have the following external components, as shown in Figure 13.

 Screw terminals
 USB connector
 Status LEDs (Command, Wireless Power, Transmit, Receive, Received Signal Strength indicators)
 LED Test button

Figure 13. OM-WLS-TC and OM-WLS-TEMP component locations

21

OM-WLS Series User's Guide Functional Details

LED

Function

Command

Steady green – the OM-WLS Series device is connected to a computer or AC adapter

Blinking green – the OM-WLS-TEMP, OM-WLS-TC and OM-WLS-IFC is receiving a
command over the USB or wireless link.

Wireless Power (green)

The internal RF module is receiving power (USB or AC adapter).

Transmit (yellow)

Data is being transmitted over an active wireless link.

Receive (red)

Data is being received over an active wireless link.

Received Signal Strength
(RSS) indicator LEDs

3 green LED bar graph. The LEDs will turn on when receiving a wireless message and stay
on for approximately 1 second after the end of the message. They indicate the amount of
fade margin present in an active wireless link. Fade margin is defined as the difference
between the incoming signal strength and the device’s receiver sensitivity.

 Three LEDs on: Very strong signal (> 30 dB fade margin)
 Two LEDs on: Strong signal (> 20 dB fade margin)
 One LED on: Moderate signal (> 10 dB fade margin)
 No LEDs on: Weak signal (< 10 dB fade margin)

Screw terminals

Use the screw terminals to connect connecting temperature sensors and digital I/O lines. These terminals also
provide ground and power output connections. Refer to the Screw terminal pinout section on page 13 for screw
terminal descriptions.

Caution! The two +5V terminals (pin 21 and pin 47) are isolated (500 VDC) from the USB +5V. Each +5V

terminal is an output. Do not connect to an external power supply or you may damage the OM­WLS-TC or OM-WLS-TEMP and possibly the computer.

USB connector

The USB connector provides +5V power and communication. External power is required to operate the
OM-WLS-TC and OM-WLS-TEMP remotely through the wireless interface.

For local operation, connect to the USB port or hub on your computer. For remote wireless operation, connect
to the external AC adapter shipped with the device.

Status LEDs

The LEDs indicate the communication status of USB and wireless operations. In addition, three LEDs indicate
the signal strength of data received over the wireless link. Refer to the table below for the function of each LED.

LED functions

LED Test button

The LED Test button tests the functionality of the LEDs. When pressed, each LED lights in sequence (first the
Command LED then left to right from the Wireless Power LED to the RSS indicator LEDs).

22

OM-WLS Series User's Guide Functional Details

1

Power LED

4

USB Activity LED

2

Received Signal Strength (RSS) indicator

5

Transmit LED

3

USB connector

6

Receive LED

LED

Function

Power

Steady green – the OM-WLS-IFC is connected to a computer or external USB hub.

Blinking green – indicates activity over the USB connection.

Received Signal Strength (RSS)
indicator

3 green LED bar graph. The LEDs turn on when receiving a wireless message, and
stay on for approximately 1 second after the end of the message.

The LEDs indicate the amount of fade margin present in an active wireless link.
Fade margin is defined as the difference between the incoming signal strength and

the device’s receiver sensitivity.

 Three LEDs on : Very strong signal (> 30 dB fade margin)
 Two LEDs on : Strong signal (> 20 dB fade margin)
 One LED on : Moderate signal (> 10 dB fade margin)
 No LEDs on: Weak signal (< 10 dB fade margin)

USB Activity (green)

Activity over the USB connection is detected.

Transmit (yellow)

Data is being transmitted over the wireless link

Receive (red)

Data is being received over the wireless link.

OM-WLS-IFC

The OM-WLS-TEMP, OM-WLS-TC and OM-WLS-IFC has the following external components, as shown in
Figure 14.

 Status LEDs (USB Activity, Transmit, Receive, Received Signal Strength indicator)
 Power LED
 USB connector

Figure 14. OM-WLS-IFC component locations

Status LEDs

The LEDs indicate the communication status of USB and wireless operations. An LED bar graph indicates the
strength of the signal received by the remote device. Refer to the table below for the function of each LED.

LED functions

Power LED

The Power LED is on when the OM-WLS-IFC is connected to a computer or external USB hub.

USB connector

The USB connector provides +5V power and communication to the OM-WLS-IFC.

23

Parameter

Conditions

Specification

A/D converters

Four dual 24-bit, Sigma-Delta type

Number of channels

8 differential

Input isolation

500 VDC minimum between field wiring and
USB interface

Channel configuration

 OM-WLS-TEMP: Software-selectable to

match sensor type

 OM-WLS-TC: Thermocouple sensor type

Differential input voltage
range for the various sensor
categories

Thermocouple

±0.080 V

RTD (OM-WLS-TEMP only)

0 to 0.5 V

Thermistor (OM-WLS-TEMP only)

0 to 2 V

Semiconductor sensor
(OM-WLS-TEMP only)

0 to 2.5 V

Absolute maximum input
voltage

±C0x through ±C7x relative to GND
(pins 9, 19, 28, 38)

±25 V power on, ±40 V power off.
Input impedance

5 GΩ, min

Input leakage current

Open thermocouple detect disabled
(OM-WLS-TEMP only)

30 nA max
Open thermocouple detect enabled

105 nA max

Normal mode rejection ratio

fIN =60 Hz

90 dB min

Common mode rejection
ratio

f

IN

=50 Hz/60 Hz

100 dB min

Resolution

24 bits

No missing codes

24 bits

Input coupling

DC

Warm-up time

30 minutes min

Open thermocouple detect

Automatically enabled when the channel pair is
configured for thermocouple sensor.
The maximum open detection time is 3 seconds.

CJC sensor accuracy

15 °C to 35 °C

±0.25 °C typ,±0.5 °C max

0 °C to 70 °C

–1.0 °C to +0.5 °C max

Specifications

All specifications are subject to change without notice.
Typical for 25 °C unless otherwise specified.

Specifications in italic text are guaranteed by design.

Analog input (OM-WLS-TEMP and OM-WLS-TC only)

Table 1. Generic analog input specifications

Chapter 5

24

OM-WLS Series User's Guide Specifications

Sensor Category

Conditions

Max number of
sensors (all channels
configured alike)

Disabled
(OM-WLS-TEMP only)

Thermocouple

J, K, S, R, B, E, T, or N

8 differential channels

Semiconductor sensor

8 differential channels

RTD and thermistor
(OM-WLS-TEMP only)

2-wire input configuration with a single sensor per
channel pair

4 differential channels
2-wire input configuration with two sensors per channel pair

8 differential channels

3-wire configuration with a single sensor per channel pair

4 differential channels

4-wire input configuration with a single sensor per
channel pair

4 differential channels
4-wire input configuration with two sensors per channel pair

8 differential channels

Parameter

Conditions

Thermocouple

J: –210 °C to 1200 °C

K: –270 °C to 1372 °C

R: –50 °C to 1768 °C

S: –50 °C to 1768 °C

T: –270 °C to 400 °C

N: –270 °C to 1300 °C

E: –270 °C to 1000 °C

B: 0 °C to 1820 °C

RTD (OM-WLS-TEMP only)

100 Ω PT (DIN 43760: 0.00385 ohms/ohm/°C)

100 Ω PT (SAMA: 0.003911 ohms/ohm/°C)

100 Ω PT (ITS-90/IEC751:0.0038505 ohms/ohm/°C)

Thermistor
(OM-WLS-TEMP only)

Standard 2,252 Ω through 30,000 Ω

Semiconductor/IC
(OM-WLS-TEMP only)

TMP36 or equivalent

Channel configurations (OM-WLS-TEMP and OM-WLS-TC only)

Table 2. Channel configuration specifications

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

differential channels. The analog input channels are therefore configured in four channel pairs
with CH0/CH1 sensor inputs, CH2/CH3 sensor inputs, CH4/CH5 sensor inputs, and CH6/CH7
sensor inputs paired together. This "channel-pairing" requires the analog input channel pairs be
configured to monitor the same category of temperature sensor. Mixing different sensor types of
the same category (such as a type J thermocouple on channel 0 and a type T thermocouple on
channel 1) is valid.

Note 2: Channel configuration information is stored in the EEPROM of the isolated microcontroller by

the firmware whenever any item is modified. Modification is performed by commands issued
over USB or wireless from an external application, and the configuration is made non-volatile
through the use of the EEPROM.

Note 3: The OM-WLS-TC factory default configuration is Type J.

The OM-WLS-TEMP factory default configuration is Disabled. The Disabled mode will
disconnect the analog inputs from the terminal blocks and internally ground all of the A/D inputs.
This mode also disables each of the current excitation sources.

Compatible sensors (OM-WLS-TEMP and OM-WLS-TC only)

Table 3. Compatible sensor type specifications

25

OM-WLS Series User's Guide Specifications

Sensor Type

Maximum error

Typical error

Temperature range

J

±1.499 °C

±0.507 °C

–210 °C to 0 °C

±0.643 °C

±0.312 °C

0 °C to 1200 °C

K

±1.761 °C

±0.538 °C

–210 °C to 0 °C

±0.691 °C

±0.345 °C

0 °C to 1372 °C

S

±2.491 °C

±0.648 °C

–50 °C to 250 °C

±1.841 °C

±0.399 °C

250 °C to 1768.1 °C

R

±2.653 °C

±0.650 °C

–50 °C to 250 °C

±1.070 °C

±0.358 °C

250 °C to 1768.1 °C

B

±1.779 °C

±0.581 °C

250 °C to 700 °C

±0.912 °C

±0.369 °C

700 °C to 1820 °C

E

±1.471 °C

±0.462 °C

–200 °C to 0 °C

±0.639 °C

±0.245 °C

0 °C to 1000 °C

T

±1.717 °C

±0.514 °C

–200 °C to 0 °C

±0.713 °C

±0.256 °C

0 °C to 600 °C

N

±1.969 °C

±0.502 °C

–200 °C to 0 °C

±0.769 °C

±0.272 °C

0 °C to 1300 °C

Sensor Type

Temperature Range (°C)

Maximum Accuracy Error

TMP36 or equivalent

–40 °C to 150 °C

±0.50 °C

Accuracy (OM-WLS-TEMP and OM-WLS-TC only)

Thermocouple measurement accuracy

Table 4. Thermocouple accuracy specifications, including CJC measurement error

Note 4: Thermocouple measurement accuracy specifications include linearization, cold-junction

compensation and system noise. These specs are for one year, or 3000 operating hours,
whichever comes first, and for operation of the device between 15 °C and 35 °C. For
measurements outside this range, add ±0.5 degree to the maximum error shown. There are CJC
sensors on each 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. Please contact your thermocouple supplier for details on the actual thermocouple error.

Note 5: Thermocouples must be connected to the device such that they are floating with respect to GND

(pins 9, 19, 28, 38). The device 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 and earth ground is maintained.

Note 6: 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.

Semiconductor sensor measurement accuracy (OM-WLS-TEMP only)

Table 5. Semiconductor sensor accuracy specifications

Note 7: Error shown does not include errors of the sensor itself. These specs are for one year while

operation of the device is between 15 °C and 35 °C. Please contact your sensor supplier for
details on the actual sensor error limitations.

26

OM-WLS Series User's Guide Specifications

RTD

Sensor
Temperature

Maximum Accuracy Error (°C)
Ix+ = 210 µA

Typical Accuracy Error (°C)
Ix+ = 210 µA

PT100, DIN, US or
ITS-90

–200 °C to –150 °C

±2.85

±2.59

–150 °C to –100 °C

±1.24

±0.97

–100 °C to 0 °C

±0.58

±0.31

0 °C to 100 °C

±0.38

±0.11

100 °C to 300 °C

±0.39

±0.12

300 °C to 600 °C

±0.40

±0.12

Thermistor

Temperature Range

Maximum Accuracy Error (°C)
Ix+ = 10 µA

2252 Ω

–40 °C to120 °C

±0.05

3000 Ω

–40 °C to120 °C

±0.05

5000 Ω

–35 °C to120 °C

±0.05

10000 Ω

–25 °C to120 °C

±0.05

30000 Ω

–10 °C to120 °C

±0.05

RTD measurement accuracy (OM-WLS-TEMP only)

Table 6. RTD measurement accuracy specifications

Note 8: Error shown does not include errors of the sensor itself. The sensor linearization is performed

using a Callendar-Van Dusen linearization algorithm. These specs are for one year while
operation of the device is between 15 °C and 35 °C. The specification does not include lead
resistance errors for 2-wire RTD connections. Please contact your sensor supplier for details on
the actual sensor error limitations.

Note 9: Resistance values greater than 660 Ω cannot be measured by the device in the RTD mode. The

660 Ω resistance limit includes the total resistance across the current excitation (±Ix) pins, which
is the sum of the RTD resistance and the lead resistances.

Note 10: For accurate three wire compensation, the individual lead resistances connected to the ±Ix pins

must be of equal value.

Thermistor measurement accuracy (OM-WLS-TEMP only)

Table 7. Thermistor measurement accuracy specifications

Note 11: Error shown does not include errors of the sensor itself. The sensor linearization is performed

using a Steinhart-Hart linearization algorithm. These specs are for one year while operation of the
device is between 15 °C and 35 °C. The specification does not include lead resistance errors for
2-wire thermistor connections. Please contact your sensor supplier for details on the actual sensor
error limitations. Total thermistor resistance on any given channel pair must not exceed 180 k Ω.
Typical resistance values at various temperatures for supported thermistors are shown in Table 8.

27

OM-WLS Series User's Guide Specifications

Temp

2252 Ω
thermistor

3000 Ω
thermistor

5 kΩ
thermistor

10 kΩ
thermistor

30 kΩ
thermistor

–40 °C

76 kΩ

101 kΩ

168 kΩ

240 kΩ (Note 12)

885 kΩ (Note 12)

–35 °C

55 kΩ

73 kΩ

121 kΩ

179 kΩ

649 kΩ (Note 12)

–30 °C

40 kΩ

53 kΩ

88 kΩ

135 kΩ

481 kΩ (Note 12)

–25 °C

29 kΩ

39 kΩ

65 kΩ

103 kΩ

360 kΩ (Note 12)

–20 °C

22 kΩ

29 kΩ

49 kΩ

79 kΩ

271 kΩ (Note 12)

–15 °C

16 kΩ

22 kΩ

36 kΩ

61 kΩ

206 kΩ (Note 12)

–10 °C

12 kΩ

17 kΩ

28 kΩ

48 kΩ

158 kΩ

–5 °C

9.5 kΩ

13 kΩ

21 kΩ

37 kΩ

122 kΩ

0 °C

7.4 kΩ

9.8 kΩ

16 kΩ

29 kΩ

95 kΩ

Number of Input Channels

Maximum Throughput

1

2 Samples/second

2

2 S/s on each channel, 4 S/s total

3

2 S/s on each channel, 6 S/s total

4

2 S/s on each channel, 8 S/s total

5

2 S/s on each channel, 10 S/s total

6

2 S/s on each channel, 12 S/s total

7

2 S/s on each channel, 14 S/s total

8

2 S/s on each channel, 16 S/s total

Table 8. Typical thermistor resistance specifications

Note 12: Resistance values greater than 180 kΩ cannot be measured by the device in the thermistor mode.

The 180 kΩ resistance limit includes the total resistance across the current excitation (±Ix) pins,
which is the sum of the thermistor resistance and the lead resistances.

Note 13: For accurate three wire compensation, the individual lead resistances connected to the ±Ix pins

must be of equal value.

Throughput rate to PC (USB or wireless) (OM-WLS-TEMP and OM-WLS-TC only)

Table 9. Throughput rate specifications

Note 14: 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 temperature data is provided
by the device is approximately 0.5 seconds

28

OM-WLS Series User's Guide Specifications

Parameter

Conditions

Digital type

CMOS

Number of I/O

8 (DIO0 through DIO7)

Configuration

Independently configured for input or output.
Power on reset is input mode unless bit is configured for alarm.

Pull up/pull-down
configuration

All pins pulled up to +5 V via 47 K kΩ resistors (default). Pull down to ground (GND)
also available.

Digital I/O transfer rate
(software paced)

 Digital input – 50 port reads or single bit reads per second typ
 Digital output – 100 port writes or single bit writes per second typ

Input high voltage

2.0 V min, 5.5 V absolute max

Input low voltage

0.8 V max, –0.5 V absolute min

Output low voltage
(IOL = 2.5 mA)

0.7 V max

Output high voltage
(IOH = –2.5 mA)

3.8 V min

Parameter

Conditions

Number of alarms

8 (one per digital I/O line)

Alarm functionality

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 in
wireless mode and while attached to USB.

Alarm input modes

 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.

Alarm output modes

 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)

Alarm update rate

1 s

Digital input/output (OM-WLS-TEMP and OM-WLS-TC only)

Table 10. Digital input/output specifications

Note 15: All ground pins on the device (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.

Temperature alarms (OM-WLS-TEMP and OM-WLS-TC only)

Table 11. Temperature alarm specifications

29

OM-WLS Series User's Guide Specifications

Parameter

Conditions

EEPROM

 OM-WLS-TEMP and OM-WLS-TC

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

 OM-WLS-IFC

256 bytes USB micro for external application use

Parameter

Conditions

Type

 OM-WLS-TEMP and OM-WLS-TC

Three high performance 8-bit RISC microcontrollers

 OM-WLS-IFC

One high performance 8-bit RISC microcontroller

Parameter

Conditions

Communication standard

IEEE 802.15.4, ISM 2.4GHz frequency band, non-beacon, point-to-point

Range

Indoor/urban: Up to 150 ft (50 m)
Outdoor RF line-of-sight: Up to ½ mile (750 m)

Transmit power output

10 mW (10 dBm)

Receiver sensitivity

–100 dBm (1% packet error rate)

RF channels

12 direct sequence channels available, channels 12 to 23 (2.410 GHz to 2.465 GHz);
software selectable

Addressing

16-bit PAN (personal area network) IDs per channel (software selectable)
64-bit device address

Encryption

128-bit AES (software selectable)

Parameter

Specification

USB +5V (VBUS) input voltage
range

4.75 V to 5.25 V

Memory

Table 12. Memory specifications

Microcontroller

Table 13. Microcontroller specifications

Wireless communications

Table 14. Wireless Communications specifications

Contains FCC ID: OUR-XBEEPRO. The enclosed device complies with Part 15 of the FCC Rules. Operation is
subject to the following two conditions: (i.) this device may not cause harmful interference and (ii.) this device
must accept any interference received, including interference that may cause undesired operation.

Note 16: Canada: Contains Model XBee Radio, IC: 4214A-XBEEPRO

Caution! To satisfy FCC RF exposure requirements for mobile transmitting devices, a separation distance

of 20 cm or more should be maintained between the antenna of this device and persons during
device operation. To ensure compliance, operations at closer than this distance is not
recommended. The antenna used for this transmitter must not be co-located in conjunction with
any other antenna or transmitter.

USB +5V voltage

Table 15. USB +5V voltage specifications

30

OM-WLS Series User's Guide Specifications

Parameter

Conditions

Specification

Connected to USB (OM-WLS-TEMP and OM-WLS-TC only)

Supply current

500 mA max

User +5V output voltage range
(terminal block pin 21 and 47)

Connected to a self-powered hub. (Note 17)

4.75 V min to

5.25 V max

User +5V output current
(terminal block pin 21 and pin 47)

Connected to a self-powered hub. (Note 17)

10 mA max

Isolation

Measurement system to PC

500 VDC min

Connected to USB (OM-WLS-IFC only)

Supply current

300 mA max

Wireless Communications operation

Supply current

500 mA max

AC Adapter Power Supply (used for remote wireless communications operation)
(OM-WLS-TEMP and OM-WLS-TC only)

Standalone power supply

USB power adapter

2.5 Watt USB adapter with
interchangeable plugs

(Includes plug for USA)

Output voltage

5 V ±5%

Output wattage

2.5 W

Input voltage

100 VAC to 240 VAC
50 Hz to 60 Hz

Input current

0.2 A

Parameter

Conditions

USB device type

USB 2.0 (full-speed)

Device compatibility

USB 1.1, USB 2.0

Bus powered.
OM-WLS-TEMP and OM-WLS-TC: 500 mA consumption max
OM-WLS-IFC: 300 mA consumption max

USB cable type

A-B cable, UL type AWM 2725 or equivalent. (min 24 AWG VBUS/GND,
min 28 AWG D+/D-)

USB cable length

3 meters max

Power

Table 16. Power specifications

Note 17: Self-Powered Hub refers to a USB hub with an external power supply. Self-powered hubs allow

a connected USB device to draw up to 500 mA. This device may not be used with bus-powered
hubs due to the power supply requirements.

Root Port Hubs reside in the PC’s USB Host Controller. The USB port(s) on your PC are root
port hubs. All externally powered root port hubs (desktop PC's) provide up to 500 mA of current
for a USB device. Battery-powered root port hubs provide 100 mA or 500 mA, depending upon
the manufacturer. A laptop PC that is not connected to an external power adapter is an example
of a battery-powered root port hub.

USB specifications

Table 17. USB specifications

31

OM-WLS Series User's Guide Specifications

Parameter

Conditions

Specification

Configuration

4 dedicated pairs:
±I1: CH0/CH1
±I2: CH2/CH3
±I3: CH4/CH5
±I4: CH6/CH7

Current excitation output ranges

Thermistor

10 µA typ

RTD

210 µA typ

Tolerance

±5% typ

Drift 200 ppm/°C

Line regulation

2.1 ppm/V max

Load regulation

0.3 ppm/V typ

Output compliance voltage
(relative to GND pins 9, 19, 28, 38)

3.90 V max
–0.03 V min

Parameter

Conditions

Operating temperature range

0 °C to 70 °C

Storage temperature range

–40 °C to 85 °C

Humidity

0% to 90% non-condensing

Parameter

Conditions

Dimensions (L W H)

 OM-WLS-TEMP and OM-WLS-TC

127.0 88.9 35.6 mm (5.0 3.5 1.4 in.)

 OM-WLS-IFC

79.0 75.0 26.5 mm (3.1 3.0 1.0 in.)

User connection length

3 meters max

Current excitation outputs (Ix+) (OM-WLS-TEMP only)

Table 18. Current excitation output specifications

Note 18: The device has four current excitation outputs, with ±I1 dedicated to the CH0/CH1 analog inputs,

±I2 dedicated to CH2/CH3, ±I3 dedicated to CH4/CH5, and ±I4 dedicated to CH6/CH7. The
excitation output currents should always be used in this dedicated configuration.

Note 19: The current excitation outputs are automatically configured based on the sensor (thermistor or

RTD) selected.

Environmental

Mechanical

Table 19. Environmental specifications

Table 20. Mechanical specifications

32

OM-WLS Series User's Guide Specifications

Parameter

Conditions

Command LED

Green LED – indicates a command was received by the device (either USB or
wireless)

Received Signal Strength Indicator
(RSSI) LEDs

Three green LED bar graph. LEDs will turn on when receiving a wireless message
and stay on for approximately 1 second after the end of the message. They indicate
the amount of fade margin present in an active wireless link. Fade margin is
defined as the difference between the incoming signal strength and the device's
receiver sensitivity.

 3 LEDs on: Very strong signal (> 30 dB fade margin)
 2 LEDs on: Strong signal (> 20 dB fade margin)
 1 LED on: Moderate signal (> 10 dB fade margin)
 0 LED on: Weak signal (< 10 dB fade margin)

Wireless Power LED

Green LED – indicates that the internal RF module is powered.

Transmit LED

Yellow LED – indicates transmitting data over the wireless link.

Receive LED

Red LED – indicates receiving data over the wireless link.

Button

Firmware defined; this revision executes an LED test.

Command

Wireless Power

Transmit

Receive

Received

Signal

Strength

Button

(firmware

defined)

LED/button configuration

OM-WLS-TEMP and OM-WLS-TC

Table 21. OM-WLS-TEMP and OM-WLS-TC LED configuration

33

OM-WLS Series User's Guide Specifications

Parameter

Conditions

Power

The OM-WLS-IFC is connected to a computer or external USB hub

Received Signal Strength Indicator
(RSSI)

3 green LED bar graph. The LEDs will turn on when receiving a wireless
message and stay on for approximately 1 second after the end of the message.
They indicate the amount of fade margin present in an active wireless link. Fade
margin is defined as the difference between the incoming signal strength and the
device's receiver sensitivity.

 3 LEDs on: Very strong signal (> 30 dB fade margin)
 2 LEDs on: Strong signal (> 20 dB fade margin)
 1 LED on: Moderate signal (> 10 dB fade margin)
 0 LEDs on: Weak signal (< 10 dB fade margin)

USB activity

Green LED – indicates activity over the USB connection

Transmit

Yellow LED – indicates transmitting data over the wireless link

Receive

Red LED – indicates receiving data over the wireless link

Power

Received

Signal
Strength
Indicator

USB

Transmit

Receive

OM-WLS-IFC

Table 22. OM-WLS-IFC LED configuration

34

OM-WLS Series User's Guide Specifications

Parameter

Conditions

Connector type

Screw terminal

Wire gauge range

16 AWG to 30 AWG

Pin

Signal Name

Pin Description

Pin

Signal Name

Pin Description

1

I1+ 1

CH0/CH1 current excitation source

27

I4– 1

CH6/CH7 current excitation return

2

NC

No connect

28

GND

Ground

3

C0H

CH0 sensor input (+)

29

C7L

CH7 sensor input (–)

4

C0L

CH0 sensor input (–)

30

C7H

CH7 sensor input (+)

5

4W01 2

CH0/CH1 4-wire, 2 sensor common

31

IC67 1

CH6/CH7 2 sensor common

6

IC01 1

CH0/CH1 2-sensor common

32

4W67 2

CH6/CH7 4-wire, 2 sensor common

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

No connect

10

I1– 1

CH0/CH1 current excitation return

36

I4+ 1

CH6/CH7 current excitation source

CJC sensor

CJC sensor
11

I2+ 1

CH2/CH3 current excitation source

37

I3– 1

CH4/CH5 current excitation return

12

NC

No connect

38

GND

Ground

13

C2H

CH2 sensor input (+)

39

C5L

CH5 sensor input (–)

14

C2L

CH2 sensor input (–)

40

C5H

CH5 sensor input (+)

15

4W23 2

CH2/CH3 4-wire, 2 sensor common

41

IC45 1

CH4/CH5 2 sensor common

16

IC23 1

CH2/CH3 2 sensor common

42

4W45 2

CH4/CH5 4-wire, 2 sensor common

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

No connect

20

I2– 1

CH2/CH3 current excitation return

46

I3+ 1

CH4/CH5 current excitation source

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

Screw terminal connector type and pinout (OM-WLS-TEMP and OM-WLS-TC only)

Table 22. Screw terminal connector specifications

Table 23. Screw terminal pinout

1

OM-WLS-TEMP only. These pins are labeled RSVD (reserved for future use) on the OM-WLS-TC.

2

OM-WLS-TEMP only. "NC" (no connection) on the OM-WLS-TC.

Do not connect anything to pins labeled "NC".

35

WARRANTY/DISCLAIMER

OMEGA ENGINEERING, INC. warrants this unit to be free of defects in materials and workmanship for a
period of 13 months from date of purchase. OMEGA’s WARRANTY adds an additional one (1) month
grace period to the normal one (1) year product warranty to cover handling and shipping time. This
ensures that OMEGA’s customers receive maximum coverage on each product.

If the unit malfunctions, it must be returned to the factory for evaluation. OMEGA’s Customer Service
Department will issue an Authorized Return (AR) number immediately upon phone or written request.
Upon examination by OMEGA, if the unit is found to be defective, it will be repaired or replaced at no
charge. OMEGA’s WARRANTY does not apply to defects resulting from any action of the purchaser,
including but not limited to mishandling, improper interfacing, operation outside of design limits,
improper repair, or unauthorized modification. This WARRANTY is VOID if the unit shows evidence of
having been tampered with or shows evidence of having been damaged as a result of excessive corrosion;
or current, heat, moisture or vibration; improper specification; misapplication; misuse or other operating
conditions outside of OMEGA’s control. Components in which wear is not warranted, include but are not
limited to contact points, fuses, and triacs.

OMEGA is pleased to offer suggestions on the use of its various products. However,
OMEGA neither assumes responsibility for any omissions or errors nor assumes liability for any
damages that result from the use of its products in accordance with information provided by
OMEGA, either verbal or written. OMEGA warrants only that the parts manufactured by the
company will be as specified and free of defects. OMEGA MAKES NO OTHER WARRANTIES OR
REPRESENTATIONS OF ANY KIND WHATSOEVER, EXPRESSED OR IMPLIED, EXCEPT THAT OF
TITLE, AND ALL IMPLIED WARRANTIES INCLUDING ANY WARRANTY OF MERCHANTABILITY
AND FITNESS FOR A PARTICULAR PURPOSE ARE HEREBY DISCLAIMED. LIMITATION OF
LIABILITY: The remedies of purchaser set forth herein are exclusive, and the total liability of
OMEGA with respect to this order, whether based on contract, warranty, negligence,
indemnification, strict liability or otherwise, shall not exceed the purchase price of the
component upon which liability is based. In no event shall OMEGA be liable for
consequential, incidental or special damages.

CONDITIONS: Equipment sold by OMEGA is not intended to be used, nor shall it be used: (1) as a “Basic
Component” under 10 CFR 21 (NRC), used in or with any nuclear installation or activity; or (2) in medical
applications or used on humans. Should any Product(s) be used in or with any nuclear installation or
activity, medical application, used on humans, or misused in any way, OMEGA assumes no responsibility
as set forth in our basic WARRANTY/DISCLAIMER language, and, additionally, purchaser will indemnify
OMEGA and hold OMEGA harmless from any liability or damage whatsoever arising out of the use of the
Product(s) in such a manner.

RETURN REQUESTS/INQUIRIES

Direct all warranty and repair requests/inquiries to the OMEGA Customer Service Department. BEFORE
RETURNING ANY PRODUCT(S) TO OMEGA, PURCHASER MUST OBTAIN AN AUTHORIZED RETURN
(AR) NUMBER FROM OMEGA’S CUSTOMER SERVICE DEPARTMENT (IN ORDER TO AVOID
PROCESSING DELAYS). The assigned AR number should then be marked on the outside of the return
package and on any correspondence.

The purchaser is responsible for shipping charges, freight, insurance and proper packaging to prevent
breakage in transit.

FOR WARRANTY

RETURNS, please have the
following information available BEFORE
contacting OMEGA:

1. Purchase Order number under which the product

was PURCHASED,

2. Model and serial number of the product under

warranty, and

3. Repair instructions and/or specific problems

relative to the product.

FOR NON-WARRANTY REPAIRS,

consult OMEGA
for current repair charges. Have the following
information available BEFORE contacting OMEGA:

1. Purchase Order number to cover the COST

of the repair,

2. Model and serial number of the product, and

3. Repair instructions and/or specific problems

relative to the product.

OMEGA’s policy is to make running changes, not model changes, whenever an improvement is possible. This affords
our customers the latest in technology and engineering.

OMEGA is a registered trademark of OMEGA ENGINEERING, INC.
© Copyright 2011 OMEGA ENGINEERING, INC. All rights reserved. This document may not be copied, photocopied,

reproduced, translated, or reduced to any electronic medium or machine-readable form, in whole or in part, without the
prior written consent of OMEGA ENGINEERING, INC.

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