SP1202S05RB-PCB/NOPB - Texas Instruments

1 http://www.national.com

June 2009

Rev - 1.1

Thermocouple Sensor Board Version 2

SP1202S05RB

Users' Guide

Table of Contents

2 http://www.national.com

1.0 Introduction............................................................................................................................ 3

2.0 Board Assembly.................................................................................................................... 3

3.0 Quick Start............................................................................................................................. 3

4.0 Functional Description........................................................................................................... 4

4.1 Operational Modes................................................................................................... 4

4.1.1 The Computer Mode................................................................................ 4

4.1.2 The Stand-Alone Mode............................................................................ 4

4.2 Signal Conditioning Circuitry.................................................................................... 4

4.2.1 Instrumentation Amplifier ......................................................................... 4

4.2.2 Level Shifting............................................................................................ 4

4.2.3 Offset and Gain Correction ...................................................................... 4

4.3 Cold Junction Reference Temperature Sensor ....................................................... 5

4.4 Power Supply........................................................................................................... 5

4.5 Negative Bias Generation........................................................................................ 5

4.6 ADC Reference Circuitry.......................................................................................... 5

4.7 ADC Serial Clock ..................................................................................................... 5

4.8 ADC Chip Select Bar................................................................................................ 5

4.9 Digital Data Output/Input.......................................................................................... 5

4.10 Power Requirements.............................................................................................. 5

5.0 Installing and Using the Thermocouple Sensor Board Version 2......................................... 5

5.1 Board Set-up............................................................................................................ 5

5.2 Quick Check of Analog Functions............................................................................ 5

5.3 Quick Check of Software and Computer Interface Operation ................................. 6

5.4 Sensor Panel Software ............................................................................................ 6

5.5 Troubleshooting ....................................................................................................... 6

6.0 Evaluation Board Specifications............................................................................................ 6

7.0 Example Hardware Schematic.............................................................................................. 7

8.0 Thermocouple Sensor Board Version 2 Example Bill of Materials....................................... 8

Summary Tables of Test Points and Connectors ....................................................................... 9

Summary Tables of Test Points and Connectors (cont'd) .......................................................... 10

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1.0 Introduction

The Thermocouple Sensor Board Version 2

(SP1202S05RB) along with the Sensor Signal Path

Control Panel (Sensor Panel) software and SPUSI2

USB Interface Dongle are designed to ease the

design of circuits using various thermocouple

sensors with National's amplifiers and Analog-to-

Digital converters (ADCs). Use the WEBENCH®

Thermocouple Sensor Designer tool to determine

appropriate IC’s and passives to achieve your signal

path requirements:

http://www.national.com/analog/webench/sensors/the

rmocouple

See Figure 1 for component placement and Figure 2

for example board schematic. The thermocouple

sensor can be connected to header J1 or J2. The

differential voltage at the thermocouple sensor output

is digitized and can be captured and displayed on the

computer monitor with the accompanying Sensor

Panel software, which operates under Microsoft

Windows XP. The amplified thermocouple sensor

voltage may be measured at TP3 relative to ground.

The software can provide gain and offset correction

for the entire circuit, including the sensor.

2.0 Board Assembly

This Thermocouple Sensor Board Version 2 comes

as a bare board that must be assembled. Refer to an

example Bill of Materials for a description of

component values, to Figure 1 for major component

placement and to Figure 2 for the example Board

schematic.

3.0 Quick Start

Refer to Figure 1 for locations of test points and

major components.

1. Place the jumpers on the following positions

Table 1 – Jumper Default Positions

Jumper Pins

Shorted FUNCTION

JP1 2 - 3 Level Shifting

JP2 2 - 3 Negative Bias Generator

JP3 2 - 3 ADC Reference Select

2. Connect the Thermocouple Sensor Board

Version 2 to a SPUSI2 (USB Interface Dongle)

via 14-pin header J3 and connect a USB cable

between the SPUSI2 board and a PC USB port.

Red LEDs D2 on the Thermocouple Sensor

Board Version 2 and D1 on the SPUSI2 board

should come on if the PC is on.

4. Connect the thermocouple sensor to connector

J1 or J2 of the board.

5. If not already installed, install the Sensor Panel

software on the PC. Run the software.

J1 Thermocouple

Connecto

J2 Thermocouple

Connecto

TP11

+5V

TP2

-IN

JP1

Level Shiftin

TP1

+IN TP4

IN1

JP2

NEG BIAS

TP9

DIN

TP5

DOUT

TP7

CSB

TP3

IN2

JP3

REF

SEL

TP10

REF

J3 ADC

Interface

TP8

3.3V

TP6

SCL

ure 1. Com

onent and Test Point Locations

4 http://www.national.com

4.0 Functional Description

The Thermocouple Board Version 2 component and

test point locations are shown in Figure 1. The board

schematic is shown in Figure 2.

4.1 Operational Modes

This board may be use in one of two modes: the

Computer Mode using the SPUSI2 USB Interface

Dongle or the Stand-Alone Mode without the use of

the SPUSI2 USB Interface Dongle and a PC.

4.1.1 The Computer Mode

The board is intended for use in the Computer Mode

with a SPUSI2 board. The Sensor Panel software

controls the measurements by communicating with

the ADC via the device’s SPI interface. Power to both

boards is provided via USB.

4.1.2 The Stand-Alone Mode

The Stand-Alone Mode does not use the SPUSI2

board to capture data and upload it to a PC. To use

the board this way, the user must provide +5V at pin

14 of header J3 as well as provide ADC clock, Chip

Select, and Data In signals to the ADC at pins 3, 1,

and 7 respectively, of J3. ADC data output is

available at pin 5 of J3. Test Points TP6, TP7, TP9

and TP5 may also be used to insert/read these

signals. The range of frequencies for the ADC clock

is 1 MHz to 4 MHz. The CS rate can be as low as

desired, but no faster than 17 times the ADC clock

rate.

4.2 Signal Conditioning Circuitry

The sensor output voltage is amplified and digitized

by U5, an ADC. The full-scale value of this voltage

after amplification will depend upon the maximum

sensor output and the component values. This

amplified voltage is presented to the ADC (U5),

whose output is at header J3.

4.2.1 Instrumentation Amplifier

If considerable noise pickup is expected on the

thermocouple sensor line an instrumentation

amplifier configuration will offer good common mode

rejection (CMR). To set up the board in the

instrumentation amplifier configuration without

supplying negative bias to the amplifier or level

shifting the thermocouple sensor voltage ensure the

jumpers are in the following position

Table 2 – Jumper Default Positions

Jumper Pins

Shorted FUNCTION

JP1 2 - 3 Level Shifting

JP2 2 - 3 Negative Bias Generator

JP3 2 - 3 ADC Reference Select

Opamps U2A and U2B form a difference-in,

difference-out amplifier which amplifies the

differential output of the thermocouple sensor. The

gain of the difference amplifier, assuming RF1 = RF2,

is the classic

Differential Gain = 1 + 2 * RF1 / RG1.

The differential output is converted to a single-ended

signal with amplifier U3A. The gain of the U3A circuit,

assuming RB1 = RB2 and RA1 = RA2, is the well-known

Single-Ended Gain = – RB1 / RA1.

The overall gain from the sensor to the ADC input,

then, is

Overall Gain = (1 + 2 * RF1 / RG1)  RB1 / RA1.

Due to the way the difference amplifier is connected

to the single-ended amplifier, the overall gain is

positive.

A low pass filter is formed by C1 = C2, and RF1 =

RF2 which has a cutoff frequency of

Cutoff Frequency = 1 / ( 2 * pi * RF1 * C1)

Additional filtering can also be provided by C5 and

RB1 and has a cutoff frequency of

Cutoff Frequency = 1 / ( 2 * pi * RB1 * C5)

The WEBENCH Thermocouple Sensor Designer tool

will provide appropriate component values to achieve

your application gain and cutoff frequency

requirements.

4.2.2 Level Shifting

In many thermocouple applications the thermocouple

sensor is used in a temperature range where only a

positive output at the (+) terminal with respect to the

(-) terminal or only a negative output is expected. If

both positive and negative voltage is expected the

board allows for an offset which is provided from a

level shifting circuit. The level shifting voltage is set

up by VREF and the RLS1-RLS2 voltage divider,

then buffered through amplifier U3B. The level

shifting voltage is

VLS = (VREF * RLS2) / (RLS2 + RLS1)

The Webench® Thermocouple Sensor Designer tool

will provide appropriate component values to achieve

your application level shifting requirements.

To add level shifting to the instrumentation amplifier

configuration change the following jumper

Table 3 – Level Shifting Jumper Positions

Jumper Pins

Shorted FUNCTION

JP1 1 - 2 Level Shifting

4.2.3 Offset and Gain Correction

The circuitry does not provide adjustment for offset

voltages. However, the Sensor Panel software does

allow for this correction.

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4.3 Cold Junction Reference Temperature

Sensor

A thermocouple sensor has the ability to measure a

temperature differential between the measured

temperature point and the reference temperature

point at the reference junction often referred to as the

cold junction. Due to this fact in order to determine

the correct absolute temperature at the measuring

point it is necessary to know the cold junction

reference temperature. This is accomplished on

board by the LM94022 Analog Temperature Sensor,

U6, who’s output is fed to the first channel of the

ADC, U5. The Sensor Panel software takes this data

then calculates the correct absolute temperature at

the measuring point. The LM94022 mV/C transfer

function can be found in the LM94022 datasheet. The

sensor is hard wired for gain setting GS = 11.

4.4 Power Supply

In Computer Mode, power to this board is supplied

through header J3 and ultimately from the host PC

via USB. In most cases, the only voltage needed for

the Thermocouple Sensor Board Version 2 is the +5V

from the USB connection. Diode D1 provides

protection against reverse polarity in the Stand-Alone

mode where an external supply is used.

The supply voltage source for the ADC (VREF on the

schematic) is selected with JP3 to be either the 4.1V

from U4, or +5V from J3.

4.5 Negative Bias Generation

In the case where the measured temperature is close

to the ambient cold junction reference temperature

and the output voltage of the amplifying amplifiers are

very low it is possible that the amplifier output may

saturate. To avoid amplifier output saturation the

board allows for a negative bias to be applied to the

V- terminal of the amplifiers. The LM2687 voltage

inverter, U1, produces a voltage of apx. – 0.25V. To

add negative bias generation to the circuit change

the following jumper

Table 6 – Neg. Bias Generator Jumper Positions

Jumper Pins

Shorted FUNCTION

JP2 1 - 2 Negative Bias Generator

4.6 ADC Reference Circuitry

The single-ended dual channel ADCXX2SXX1 uses its

supply voltage as its reference, so it is important that

its supply voltage be stable and quiet. A 4.1V

reference voltage is provided by U4, an accurate

LM4120-4.1.

4.7 ADC Serial Clock

The ADC clock signal (SCLK) is provided external to the

board at header J3 on pin 3 or TP6. The requirements

for SCLK can be found in the respective ADC datasheet.

4.8 ADC Chip Select Bar

The ADC chip select bar (CSB) is provided external

to the board at header J3 on pin 1 or on TP7. The

requirements for CSB with respect to SCLK can be

found in the respective ADC datasheet.

4.9 Digital Data Output/Input

The digital output data from the ADC is available at

14-pin header J3 on pin 5 or on TP5. The digital input

data to the ADC is available at 14-pin header J3 on

pin 7 or on TP9.

4.10 Power Requirements

Voltage and current requirements for the

Thermocouple Sensor Board Version 2 are:

 Pin 14 of J3: +5.0V at 30 mA

 Pins 2 and 4 of J3: Ground

5.0 Installing and Using the Thermocouple

Sensor Board Version 2

The Thermocouple Sensor Board Version 2 requires

power as described above. The thermocouple sensor

should be connected to J1 or J2.

5.1 Board Set-up

Refer to Figure 1 for locations of connectors, test

points and jumpers on the board.

1. Connect The Thermocouple Sensor Board

Version 2 to a SPUSI2 USB Interface Dongle.

2. Be sure all jumpers are in place per Table 2.

3. Connect the thermocouple sensor to J1 or J2.

4. Connect a USB cable to the SPUSI2 board and a

PC.

5. Confirm that Red LED D2 on the Thermocouple

Sensor Board Version 2 is on, indicating the

presence of power to the board.

5.2 Quick Check of Analog Functions

Refer to Figure 1 for locations of connectors and test

points and jumpers on the board. If at any time the

expected response is not obtained, see Section 5.5

on Troubleshooting.

1. Perform steps 1 through 4 of Section 5.1.

2. Check for 5.0V at TP11 and for 4.1V at TP10.

3. Apply a known voltage, Vin, at J1 or J2 connector

and based on chosen gain, Av, of circuit confirm

that voltage, Vout, at TP3 is as expected (Vin x

Av = Vout).

4. Check temperature sensor output voltage at TP4

is as expected according to the transfer table

found in the LM94022 datasheet. Room temp is

apx. 2.3V.

5. Check negative bias generator output voltage at

pin 1 of JP2 is apx. -0.25V.

6. Check level shifting output voltage at pin 1 of JP1

is VLS = (VREF * RLS2) / (RLS2 + RLS1)

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This completes the quick check of the analog portion

of the evaluation board.

5.3 Quick Check of Software and Computer

Interface Operation

1. Perform steps 1 through 4 of Section 5.1.

2. Run the Sensor Panel software.

3. Select the SPI202S05RB

4. Manually enter the following data:

 Thermocouple Type

 Amplifier Configuration

 Gain

 Level Shifting Voltage

 Number of bits

 ADC Reference Voltage

The software will display the cold junction reference

temperature and the thermocouple measured

temperature.

This completes the quick check of the software and

computer interface.

5.4 Sensor Panel Software

The Sensor Panel software is available on the web at

http:\\www.national.com

Upon loading the software and running it, it is

necessary to configure it for the board you are using.

See the Sensor Panel software User’s Guide for

more details.

5.5 Troubleshooting

If there is no output from the board, check the

following:

 Be sure that the proper voltages and polarities

are present at TP11 (+5V) and TP10 (+4.1V or

+5V, as selected with JP3).

 Be sure there is a clock signal at TP6 when trying

to capture data.

 Confirm thermocouple sensor is connected

properly.

If the ADC output is zero or a single code, check the

following:

 Be sure that the proper voltages and polarities

are present at TP11 (+5V) and TP10 (+4.1V or

+5V, as selected with JP3).

 Be sure that J3 is properly connected to a

SPUSI2 USB Interface Dongle, and that there is

a jumper on JP3.

 Confirm thermocouple sensor is connected

properly.

If excessive noise is seen on the board, check the

following:

 Locate and remove possible noise sources

(Laptop AC Adapters, Equipment, etc.)

 Connect ground of board (i.e. TPG1) to an

external ground source.

6.0 Evaluation Board Specifications

Board Size: 2.85" x 2.30" (7.2 cm x 5.8 cm)

Power Requirements: +5V (30mA) at J3 pin 14

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7.0 Example Hardware Schematic

Figure 2. Thermocouple Sensor Board Version 2 Schematic

8 http://www.national.com

8.0 Thermocouple Sensor Board Version 2 Example Bill of Materials

Item

# Quantity Reference Part Reference

1 4 C1, C2, C5, CS1 Capacitor, Ceramic, 330pF, SMT, 0603,NPO, 50V, 5% MURATA #

GRM1885C1H331JA01D

Digi-key # 490-1439-1-ND

2 3 C3, C7, C15 Capacitor, Tantalum, 4.7uF, SMT, 3528, 10V, 10% VISHAY # 293D475X9010B2TE3

Digi-Key # 718-1147-1-ND

3 8

C4, C6, C8, C9, C11, C13, C16,

C19 Capacitor, Ceramic, 0.1uF, SMT, 0603, X7R, 25V, 10% TDK # C1608X7R1E104K

Digi-key # 445-1316-1-ND

4 2 C10, C17 Capacitor, Tantalum, 10uF, SMT, 3528, 10V, 10% VISHAY # 293D106X9010B2TE3

Digi-key # 718-1122-1-ND

5 1 C12 NOT STUFFED

6 1 C14 Capacitor, Ceramic, 0.033uF, SMT, 0603, X7R, 50V,

10% MURATA #

GRM188R71H333KA61D

Digi-key # 490-3286-1-ND

7 1 C18 Capacitor, , Ceramic, 0.001uF, SMT, 0603, X 7R, 50V,

10% KEMET # C0603C102K5RACTU

Digi-key # 399-1082-1-ND

8 4 CN1, CN2, CN3, CN4 Capacitor, Ceramic, 1uF, SMT, 1206, 16V, 10% JOHANSON # 160R18W105KV4E

Digi-key # 709-1068-1-ND

9 1 D1 DIODE, 50V, 1A MCC # GS1A-TP

Digi-key # GS1A-TPCT-ND

10 1 D2 RED LED LITE-ON # LTST-C930KAKT

Digi-key # 160-1461-1-ND

11 1 J1 Terminal Block ON SHORE # ED120/2DS

Digi-key # ED1609-ND

12 1 J2 Thermocouple Connector OMEGA #PCC-SMP

13 1 J3 ADC INTERFACE TYCO # 87230-7

Digi-key # A26599-ND

14 3 JP1, JP2, JP3 3-PIN HEADER Waldom/Molex # 22-28-4033

Digi-key # WM6503-ND

15 1 R1 Resistor, SMT, 0603, 1%, 43.0 ohm Panasonic # ERJ-3EKF43R0V

Digi-key # P43.0HCT-ND

16 1 R2 'Resistor, SMT, 0603, 1%, 1.00Kohm Panasonic # ERJ-3EKF1001V

Digi-key # P1.00KHCT-ND

17 2 RA1, RA2 'Resistor, SMT, 0603, 0.1%, 1.00Kohm Panasonic # ERA-3AEB102V

Digi-key # P1.0KDBCT-ND

18 2 RB1, RB2 Resistor, SMT, 0603, 0.1%, 2.00Kohm Panasonic # ERA-3AEB202V

Digi-key # P2.0KDBCT-ND

19 2 RF1, RF2 'Resistor, SMT, 0603, 0.1%, 10.0Kohm Panasonic # ERA-3AEB103V

Digi-key # P10KDBCT-ND

20 1 RG1 Resistor, SMT, 0603, 1%, 453ohm Panasonic # ERJ-3EKF4530V

Digi-key # P453HCT-ND

21 2 RLS1, RLS2 Resistor, SMT, 0603, 1%, 4.75Kohm Panasonic # ERJ-3EKF4751V

Digi-key # P4.75KHCT-ND

22 1 RN1 Resistor, SMT, 0603, 1%, 261Kohm Panasonic # ERJ-3EKF2613V

Digi-key # P261KHCT-ND

23 1 RN2 Resistor, SMT, 0603, 1%, 191Kohm Panasonic #ERJ-3EKF1913V

Digi-key # P191KHCT-ND

24 1 RN3 Resistor, SMT, 0603, 1%, 82.0Kohm Panasonic # ERJ-3EKF8202V

Digi-key # P82.0KHCT-ND

25 1 RN4 Resistor, SMT, 0603, 1%, 47.0Kohm Panasonic #ERJ-3EKF4702V

Digi-key # P47.0KHCT-ND

26 1 RS1 Resistor, SMT, 0603, 1%, 10ohm Panasonic # ERJ-3EKF10R0V

Digi-key # P10.0HCT-ND

27 14 TP1-TP11, TPG1-TPG3 TEST POINTS (NOT STUFFED)

28 1 U1 LM2687 NSC # LM2687MM/NOPB

Digi-key # LM2687MMCT-ND

29 2 U2, U3 LMP7732MM NSC # LMP7732MM/NOPB

Digi-key # LMP7732MA-ND

30 1 U4 LM4120AIM5-4.1 NSC # LM4120AIM5-4.1/NOPB

Digi-key # LM4120AIM5-4.1CT-ND

31 1 U5 ADC122S021CIMM NSC # ADC122S021CIMM

Digi-key # ADC122S021CIMMCT-

32 1 U6 LM94022 NSC # LM94022QBIMG/NOPB

Digi-key # LM94022QBIMGCT-ND

33 1 VR1 LM385-2.5 NSC # LM385M3-2.5/NOPB

Digi-key # LM385M3-2.5CT-ND

9 http://www.national.com

APPENDIX

Summary Tables of Test Points and Connectors

Test Points on the Thermocouple Sensor Board Version 2

Identifier Name Function

TP 1 +IN +IN of U2A amplifier

TP 2 -IN +IN of U2B amplifier

TP 3 ADC_IN2 ADC Channel 2 input voltage

TP 4 ADC_IN1 ADC Channel 1 input voltage

TP 5 DOUT DOUT output from ADC

TP 6 SCLK SCLK input for ADC

TP 7 CSb CSb input for ADC

TP 8 +3V3 +3.3V from SPUSI2 Board (not used on this board)

TP 9 DIN DIN input for ADC

TP 10 VREF Supply/Reference voltage of ADC

TP 11 +5V Overall supply for board from SPUSI2 Board

J1/J2 Connector - Sensor Interface

Identifier Name Function

J1/J2-1 +Out + Output from Sensor

J1/J2-2 -Out - Output from Sensor

J3 Connector - Connection to SPUSI2 Board

J3 Pin Number Voltage or Signal

1 CSb input to ADC

2 Ground

3 SCLK input to ADC

4 Ground

5 SDATA output from ADC

6 no connection

7 DIN input to ADC

8 no connection

9 no connection

10 no connection

11 no connection

12 no connection

13 +3.3V from SPUSI2 USB Interface Dongle

14 +5V from SPUSI2 USB Interface Dongle

10 http://www.national.com

Summary Tables of Test Points and Connectors (cont'd)

JP1 Jumper – Level Shifting

Shorted Positions Results

1 - 2 Level shifting enabled

2 - 3 Level shifting disabled

JP2 Jumper – Negative Bias Generator

Shorted Positions Results

1 - 2 Negative bias generation enabled

2 - 3 Negative bias generation disabled

JP3 Jumper – ADC Reference Select

Shorted Positions Results

1 - 2 +5V for ADC supply and reference voltage

2 - 3 +4.1V for ADC supply and reference voltage

11 http://www.national.com

[blank page]

12 http://www.national.com

The Thermocouple Sensor Board Version 2 is intended for product evaluation purposes only and is not intended for resale to end

consumers, is not authorized for such use and is not designed for compliance with European EMC Directive 89/336/EEC.

National does not assume any responsibility for use of any circuitry or software supplied or described. No circuit patent licenses are implied.

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(b) support or sustain life, and whose failure to perform,

when properly used in accordance with instructions for use

provided in the labeling, can be reasonably expected to

result in a significant injury to the user.

2. A critical component is any component in a life support

device or system whose failure to perform can be reasonably

expected to cause the failure of the life support device or

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