Lakeshore 231, 231P, and 234 Temperature Transmitters User manual

Brand: Lakeshore

Model: 231, 231P, and 234 Temperature Transmitters

Type: User manual

Rev. 1.8 P/N 119-021 03 October 2013

User’s Manual

Model 231 / 231P

Temperature Transmitter

Includes Coverage for:

Model 2308-01 Benchtop Enclosure

Model 2308-12 VMEbus Rackmount Case

For Use With The Following Lake Shore Sensors:

Model DT-414 Unencapsulated Silicon Diode Temperature Sensors

Series DT-420 Miniature Silicon Diode Temperature Sensors

Series DT-470 Silicon Diode Temperature Sensors

Series DT-471 Silicon Diode Temperature Sensors

Series DT-670 Silicon Diode Temperature Sensors

Series PT-100 Platinum Resistance Thermometers

Series TG-120 GaAlAs Diode Temperature Sensors

Lake Shore Cryotronics, Inc.

575 McCorkle Boulevard

Westerville, Ohio 43082-8888 USA

E-Mail Addresses:

[email protected]

Visit Our Website:

www.lakeshore.com

Fax: (614) 891-1392

Telephone: (614) 891-2243

Methods and apparatus disclosed and described herein have been developed solely on company funds of Lake

Shore Cryotronics, Inc. No government or other contractual support or relationship whatsoever has existed which in

any way affects or mitigates proprietary rights of Lake Shore Cryotronics, Inc. in these developments. Methods and

apparatus disclosed herein may be subject to U.S. Patents existing or applied for. Lake Shore Cryotronics, Inc.

reserves the right to add, improve, modify, or withdraw functions, design modifications, or products at any time

without notice. Lake Shore shall not be liable for errors contained herein or for incidental or consequential damages

in connection with furnishing, performance, or use of this material.

Lake Shore Model 231 User’s Manual

LIMITED WARRANTY STATEMENT – WARRANTY PERIOD: THREE (3) YEAR

1. Lake Shore warrants that products manufactured by Lake Shore (the "Product") will be free from

defects in materials and workmanship for three years from the date of Purchaser's physical

receipt of the Product (the "Warranty Period"). If Lake Shore receives notice of any such defects

during the Warranty Period and the defective Product is shipped freight prepaid back to Lake

Shore, Lake Shore will, at its option, either repair or replace the Product (if it is so defective)

without charge for parts, service labor or associated customary return shipping cost to the

Purchaser. Replacement for the Product may be by either new or equivalent in performance to

new. Replacement or repaired parts, or a replaced Product, will be warranted for only the

unexpired portion of the original warranty or 90 days (whichever is greater).

2. Lake Shore warrants the Product only if the Product has been sold by an authorized Lake Shore

employee, sales representative, dealer or an authorized Lake Shore original equipment

manufacturer (OEM).

3. The Product may contain remanufactured parts equivalent to new in performance or may have

been subject to incidental use when it is originally sold to the Purchaser.

4. The Warranty Period begins on the date of Purchaser's physical receipt of the Product or later

on the date of operational training and verification (OT&V) of the Product if the service is

performed by Lake Shore, provided that if the Purchaser schedules or delays the Lake Shore

OT&V for more than 30 days after delivery then the Warranty Period begins on the 31st day

after Purchaser's physical receipt of the Product.

5. This limited warranty does not apply to defects in the Product resulting from (a) improper or

inadequate installation (unless OT&V services are performed by Lake Shore), maintenance,

repair or calibration, (b) fuses, software, power surges, lightning and non-rechargeable

batteries, (c) software, interfacing, parts or other supplies not furnished by Lake Shore, (d)

unauthorized modification or misuse, (e) operation outside of the published specifications, (f)

improper site preparation or site maintenance (g) natural disasters such as flood, fire, wind, or

earthquake, or (h) damage during shipment other than original shipment to you if shipped

through a Lake Shore carrier.

6. This limited warranty does not cover: (a) regularly scheduled or ordinary and expected

recalibrations of the Product; (b) accessories to the Product (such as probe tips and cables,

holders, wire, grease, varnish, feed throughs, etc.); (c) consumables used in conjunction with

the Product (such as probe tips and cables, probe holders, sample tails, rods and holders,

ceramic putty for mounting samples, Hall sample cards, Hall sample enclosures, etc.); or, (d)

non-Lake Shore branded Products that are integrated with the Product.

7. To the extent allowed by applicable law,, this limited warranty is the only warranty applicable to

the Product and replaces all other warranties or conditions, express or implied, including, but

not limited to, the implied warranties or conditions of merchantability and fitness for a particular

purpose. Specifically, except as provided herein, Lake Shore undertakes no responsibility that

the products will be fit for any particular purpose for which you may be buying the Products. Any

implied warranty is limited in duration to the warranty period. No oral or written information, or

advice given by the Company, its Agents or Employees, shall create a warranty or in any way

increase the scope of this limited warranty. Some countries, states or provinces do not allow

limitations on an implied warranty, so the above limitation or exclusion might not apply to you.

This warranty gives you specific legal rights and you might also have other rights that vary from

country to country, state to state or province to province.

8. Further, with regard to the United Nations Convention for International Sale of Goods (CISC,) if

CISG is found to apply in relation to this agreement, which is specifically disclaimed by Lake

Shore, then this limited warranty excludes warranties that: (a) the Product is fit for the purpose

for which goods of the same description would ordinarily be used, (b) the Product is fit for any

particular purpose expressly or impliedly made known to Lake Shore at the time of the

conclusion of the contract. (c) the Product is contained or packaged in a manner usual for such

goods or in a manner adequate to preserve and protect such goods where it is shipped by

someone other than a carrier hired by Lake Shore.

9. Lake Shore disclaims any warranties of technological value or of non-infringement with respect

to the Product and Lake Shore shall have no duty to defend, indemnify, or hold harmless you

from and against any or all damages or costs incurred by you arising from the infringement of

patents or trademarks or violation or copyrights by the Product.

10. THIS WARRANTY IS NOT TRANSFERRABLE. This warranty is not transferrable.

11. Except to the extent prohibited by applicable law, neither Lake Shore nor any of its

subsidiaries, affiliates or suppliers will be held liable for direct, special, incidental, consequential

Rev. 1.8 P/N 119-021 03 October 2013

or other damages (including lost profit, lost data, or downtime costs) arising out of the use,

inability to use or result of use of the product, whether based in warranty, contract, tort or other

legal theory, regardless whether or not Lake Shore has been advised of the possibility of such

damages. Purchaser's use of the Product is entirely at Purchaser's risk. Some countries, states

and provinces do not allow the exclusion of liability for incidental or consequential damages, so

the above limitation may not apply to you.

12. This limited warranty gives you specific legal rights, and you may also have other rights that

vary within or between jurisdictions where the product is purchased and/or used. Some

jurisdictions do not allow limitation in certain warranties, and so the above limitations or

exclusions of some warranties stated above may not apply to you.

Except to the extent allowed by applicable law, the terms of this limited warranty statement do not

exclude, restrict or modify the mandatory statutory rights applicable to the sale of the product to

you. CERTIFICATION

Lake Shore certifies that this product has been inspected and tested in accordance with its

published specifications and that this product met its published specifications at the time of

shipment. The accuracy and calibration of this product at the time of shipment are traceable to the

United States National Institute of Standards and Technology (NIST); formerly known as the

National Bureau of Standards (NBS), or to a recognized natural standard.

TRADEMARK ACKNOWLEDGEMENT

Manufacturers and sellers claim many designations as trademarks to distinguish their products.

Where those designations appear in this manual and Lake Shore was aware of a trademark claim,

the designations appear in initial capital letters with a ™ or ® symbol.

Apiezon® is a trademark of Biddle Instruments.

CalCurve™, Carbon-Glass™, Cernox™, Duo-Twist™, High-Temperature Cernox™, Quad-

Lead™, Quad-Twist™, Rox™, SoftCal™, and Thermox™ are trademarks of Lake Shore

Cryotronics, Inc.

Teflon® is a trademark of DuPont De Nemours.

reserved. No portion of this manual may be reproduced, stored in a retrieval system, or

transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or

otherwise, without express written permission of Lake Shore.

Lake Shore Model 231 User’s Manual

Table of Contents

TABLE OF CONTENTS

Chapter/Paragraph Title Page

1 INTRODUCTION .......................................................................... 1-1

1.0 General .......................................................................... 1-1

1.1 Model 231 System Description ...................................... 1-1

1.2 Single Enclosure Case Description ................................ 1-6

1.3 Multiple Unit Enclosure Case Description ...................... 1-7

2 INSTALLATION ........................................................................... 2-1

2.0 General .......................................................................... 2-1

2.1 Inspection and Unpacking .............................................. 2-1

2.2 Repackaging For Shipment ........................................... 2-1

2.3 Sensor Installation Recommendations........................... 2-2

2.3.1 Two-Lead vs. Four-Lead Measurements .................... 2-2

2.3.1.1 Two-Lead Measurements ....................................... 2-2

2.3.1.2 Four-Lead Measurements ...................................... 2-3

2.3.2 Connecting Leads To The Sensor .............................. 2-3

2.3.3 Sensor Mounting ........................................................ 2-3

2.3.4 Measurement Errors Due To AC Noise ...................... 2-4

2.4 Sensor Curve Definition ................................................. 2-5

2.5 Power Connections ........................................................ 2-6

3 OPERATION ................................................................................ 3-1

3.0 General .......................................................................... 3-1

3.1 PCB DIP Switch Settings ............................................... 3-1

3.2 Output to Temperature Conversion ............................... 3-2

4 SERVICE ..................................................................................... 4-1

4.0 General .......................................................................... 4-1

4.1 General Troubleshooting ............................................... 4-1

4.1.1 No Output (On-Board LED Off) .................................. 4-1

4.1.2 Output Stops Before Reaching Upper Limit ............... 4-1

4.1.3 Output Is Incorrect Value (Small Error) ...................... 4-1

4.1.4 Output Is Incorrect Value (Large Error) ...................... 4-2

4.2 Model 231 Connector Definitions ................................... 4-2

4.3 Calibration ...................................................................... 4-3

4.3.1 Test Equipment Required ........................................... 4-3

4.3.2 Reference Calibration ................................................. 4-4

4.3.3 Output Calibration ...................................................... 4-5

Lake Shore Model 231 User’s Manual

Table of Contents

TABLE OF CONTENTS (Continued)

Chapter/Paragraph Title Page

5 OPTIONS AND ACCESSORIES ................................................. 5-1

5.0 General .......................................................................... 5-1

5.1 Enclosures ..................................................................... 5-1

5.2 Options........................................................................... 5-1

5.3 Accessories .................................................................... 5-2

5.4 Wires .............................................................................. 5-2

5.5 Sensors .......................................................................... 5-3

5.6 Special Equipment ......................................................... 5-3

APPENDIX A – MODEL 231 CURVE TABLES ................................. A-1

APPENDIX B – GLOSSARY OF TERMINOLOGY ............................ B-1

LIST OF ILLUSTRATIONS

Figure No. Title Page

1-1 Typical Model 231 Front Panel.............................................. 1-2

1-2 Single Enclosure Case Physical Dimensions ........................ 1-6

1-3 Multiple Unit Case Physical Dimensions ............................... 1-8

2-1 Typical Wall Plug-In Power Supply ....................................... 2-7

3-1 Model 231 DIP Switch (S1) ................................................... 3-1

4-1 Front Panel Connectors J2 & J3 Details ............................... 4-2

4-2 VMEbus Connector J1 Details .............................................. 4-3

4-3 Model 231 PCB Layout ......................................................... 4-4

LIST OF TABLES

Table No. Title Page

1-1 Model 231 Input Specifications ............................................. 1-3

1-2 Model 231P Input Specifications ........................................... 1-4

1-3 Model 231 & 231P Output Specifications .............................. 1-5

1-4 Model 2308-12 VMEbus Rackmount Case Specs ................ 1-7

2-1 Effect of Current Variation on Diode Temperature ................ 2-5

2-2 Typical DT-470 dV/dI Values for Selected Temps ................. 2-5

3-1 Conversion Parameters for Temperature in K ....................... 3-2

A-1 Lake Shore Standard Diode Curves ......................................A-1

A-2 Series PT-100 Platinum Resistance Curve ...........................A-2

Lake Shore Model 231 User’s Manual

Introduction 1-

CHAPTER 1

INTRODUCTION

1.0 GENERAL

Lake Shore Cryotronics designed and manufactures the Model 231 in the

United States of America. In general, reference to the Model 231 means

both the Model 231 and 231P. Specific references are made where

appropriate. This chapter provides a general description with specifications

in Paragraph 1.1, single-enclosure case description in Paragraph 1.2, and

multiple-unit enclosure case description in Paragraph 1.3.

We welcome comments on this manual. Although we try to keep it error-free,

some may occur. To report an error, describe it briefly and include the

appropriate paragraph, figure, table, and page number. Send comments to

Lake Shore Cryotronics, Attn: Technical Publications, 575 McCorkle Blvd.,

Westerville, Ohio 43082-8888. This manual is subject to change without

notice.

1.1 MODEL 231 GENERAL DESCRIPTION

The Model 231 Temperature Transmitter is available as a stand-alone unit or

for use within either of two enclosures: a Model 2308-1 single-space

enclosure, or a Model 2308-12 rackmount case that holds up to 12 units.

The Model 231 Temperature Transmitter sends temperature data from its

position near a sensor to a data acquisition channel or strip chart recorder. It

operates with Silicon diode or Gallium-Aluminum-Arsenide (GaAlAs) diode

sensors. Lake Shore Silicon diode sensors are accurate over a wide

cryogenic temperature range and are interchangeable for some applications.

The Lake Shore Series TG-120 GaAlAs diodes operate in a low to moderate

magnetic field. Excited with a 10 µA current source from the Model 231, the

sensors produce a voltage that depends on temperature. A microcontroller

reads the voltage through an A/D converter and translates it into

temperature. Either the standard temperature curve or an optional

CalCurve™ relates voltage to temperature (the Series TG-120 requires a

CalCurve).

The Model 231P uses a Series PT-100 Platinum Thermometer. The Model

231P excites the sensor with a 500 µA current to produce a measurable

signal. Either the standard platinum curve (DIN 437600) or a CalCurve is

used for temperature conversion.

Lake Shore Model 231 User’s Manual

Introduction

Once the Model 231 obtains temperature data, it

transmits it as a current from 4 to 20 mA. The

current output changes linearly with sensor

temperature. Output scale depends on the selected

temperature range. Several switch selected ranges

are available. For highest accuracy and sensitivity,

set the output for a narrow temperature band. An

optional 0 to 20 mA output is also available to

convert output to a voltage reading scaled from zero.

A 500  ±0.02% precision resistor is provided for

this purpose. This resistor produces the maximum

full-scale output of 10 V.

A single +5 VDC supply powers Model 231 circuitry.

The outputs are isolated so several 231s can

operate from the same supply without interference.

The +5 VDC can also be supplied from the pins on

the VME bus connector.

Mechanical mounting is easy because the

Model 231 is built on a standard size VME card.

It fits directly into a single height (3U) VME card

holder. The transmitter does not use the electrical

bus format, only its physical shape and power

supply.

Figure 1-1. Typical

Model 231 Front Panel

Lake Shore Model 231 User’s Manual

Introduction 1-

Table 1-1. Model 231 Input Specifications

Thermometry:

Number of Inputs: One input

Measurement Type: Four-lead differential

Sensor Type: Silicon diode, GaAlAs diode (to 5V)

Sensor Temp. Coefficient: Negative

Sensor Units: Volt (V)

Input Range: 0 – 5 volts

Sensor Excitation: 10 µA ±0.1% DC current

Update Rate: 5 readings per second

CalCurve Storage: 1 curve, loaded in PROM at factory

Example Lake Shore Sensor: DT-470-CO

Temperature Range: 1.4 K – 325 K with DT-470

Standard Curve: Curve 10

Typical Sensor Sensitivity: –30 mV/K at 4.2 K

–1.9 mV/K at 77.35 K

–2.4 mV/K at 300 K

Measurement Resolution:

Sensor Units: 76.3 µV

Temp. Equivalence: 2.5 mK at 4.2 K

40 mK at 77.35 K

32 mK at 300 K

Measurement Accuracy:

Sensor Units: ±75 µV ±0.01% of reading

Temp. Accuracy *: ±0.07 K at 4.2 K

±0.16 K at 77.35 K

±0.12 K at 300 K

* DT-470-CO with 8001 CalCurve.

Measurement Temperature Coefficient:

Sensor Units: 0.0006% of voltage reading per °C

Temp. Equivalence: 3 mK/°C at 4.2 K

3 mK/°C at 77.35 K

1.2 mK/°C at 300 K

Typical Performance With Series TG-120 Sensor:

Similar to selected example diode sensor with improved

measurement resolution and temperature resolution at

temperatures of 4 K to 50 K. Sensor voltage must not

exceed 5 V at lowest operating temperature.

Lake Shore Model 231 User’s Manual

Introduction

Table 1-2. Model 231P Input Specifications

Thermometry:

Number of Inputs: One input

Measurement Type: Four-lead differential

Sensor Type: Platinum

Sensor Temp. Coefficient: Positive

Sensor Units: Ohm ()

Input Range: 0 – 312 

Sensor Excitation: 500 µA ±0.02% DC current

Update Rate: 5 readings per second.

CalCurve Storage: 1 curve, loaded in PROM at factory.

Example Lake Shore Sensor: PT-103

Temperature Range: 14 K – 873 K with PT-103

Standard Curve: DIN 43760

Typical Sensor Sensitivity: 0.19 /K @ 30 K

0.42 /K @ 77.35 K

0.39 /K @ 300 K

0.34 /K typical up to 800 K

Measurement Resolution:

Sensor Units: 4.8 m

Temp. Equivalence: 22 mK at 30 K

11 mK at 77.35 K

13 mK at 300 K

14 mK typical up to 800 K

Measurement Accuracy:

Sensor Units: Ohms ()

Temp. Accuracy: ±0.2 K at 30 K

±0.15 K at 77.35 K

±0.3 K at 300 K

±0.7 K typical up to 800 K

Measurement Temperature Coefficient:

Sensor Units: 0.002% of voltage reading per °C

Temp. Equivalence: 0.4 mK/°C at 30 K

1 mK/°C at 77.35 K

6 mK/°C at 300 K

18 mK/°C at 800 K

Magnetic Field Use: Up to 19 teslas for T > 30 K.

Lake Shore Model 231 User’s Manual

Introduction 1-

Table 1-3. Model 231 and 231P Output Specifications

Output:

Number of Outputs: One

Output Type: Current source, isolated from power source but not

sensor input

Output Range: 4 – 20 mA or 0 – 20 mA (for 0 – 10 V with provided

500 , 0.02%, 25 ppm resistor)

Output Compliance: 10 V (500  max load)

Output Temperature Ranges: 0 – 20 K, 0 – 100 K, 0 – 200 K,

0 – 325 K, 0 – 475 K, and 0 – 1000 K

4 – 20 mA Output:

Output Resolution:

Current: ±1.22 µA ±0.006% of full scale

Temp. Equivalence: 0–20 K = 1.5 mK 0–325 K = 24.8 mK

0–100 K = 7.6 mK 0–475 K = 36.2 mK

0–200 K = 15.3 mK 0–1000 K = 76.3 mK

Output Accuracy:

Current: ±2 µA ±0.01% of full scale

Temp. Equivalence: 0–20 K = 2.5 mK 0–325 K = 41 mK

0–100 K = 12.5 mK 0–475 K = 59 mK

0–200 K = 25 mK 0–1000 K = 125 mK

Output Temperature Coefficient:

Current (% output/°C ambient): ±0.0055%/°C

Temp. Equivalence: 0–20 K = 1 mK/°C 0–325 K = 18 mK/°C

0–100 K = 6 mK/°C 0–475 K = 26 mK/°C

0–200 K = 12 mK/°C 0–1000 K = 55 mK/°C

0 – 20 mA Output (0-10 V w/500 , 0.02% Load Resistor):

Output Resolution:

Voltage: 0.6 mV ±0.006% of full scale

Temp. Equivalence: 0–20 K = 1.2 mK 0–325 K = 19.8 mK

0–100 K = 6.1 mK 0–475 K = 29 mK

0–200 K = 12.2 mK 0–1000 K = 61 mK

Output Accuracy:

Voltage: ±3 mV ±0.03% of full scale

Temp. Equivalence: 0–20 K = 6 mK 0–325 K = 98 mK

0–100 K = 30 mK 0–475 K = 143 mK

0–200 K = 60 mK 0–1000 K = 300 mK

Output Temperature Coefficient:

Voltage (% Output/°C ambient): ±0.008%/°C

Temp. Equivalence: 0–20 K = 2 mK/°C 0–325 K = 26 mK/°C

0–100 K = 8 mK/°C 0–475 K = 38 mK/°C

0–200 K = 16 mK/°C 0–1000 K = 80 mK/°C

Lake Shore Model 231 User’s Manual

Introduction

Table 1-3 Model 231 & 231P Output Specifications (Continued)

General:

Ambient Temperature Range: 15 – 35 °C

Power Requirement: +5 (±0.25) VDC, 500 mA

Size: 100 mm high × 160 mm deep × 30.5 mm wide

Mounting: VME end panel and back plane. Transmitter does

not use electrical bus format, only its physical shape and

power supply.

Note: Electronic temperature accuracy in a given temperature

range is the sum of temperature accuracies of input and output.

Sensor calibration errors are not included.

1.2 SINGLE ENCLOSURE CASE DESCRIPTION

Holds one Model 231. Typical dimensions appear below.

Figure 1-2. Typical Single Enclosure Case Physical Dimensions

Lake Shore Model 231 User’s Manual

Introduction 1-

1.3 MULTIPLE UNIT ENCLOSURE CASE DESCRIPTION

The Model 2308-12 VMEbus Rackmount Case holds up to 12 Model 231

units. A +5 VDC power supply with universal input is provided with the case.

Specifications and typical dimensions of the case are shown below. Refer to

Paragraph 2.5 for further information on the built-in power supply.

CAUTION: The Model 2308-12 bus is designed only to power multiple

Model 231s. Do not use with standard VME cards.

Table 1-4. Model 2308-12 VMEbus Rackmount Case Specifications

No. of Card Slots: 12

Size: 45 × 17.8 × 26 centimeters (17.7 × 7 × 10.25 inches)

Weight: 5.5 kilograms (12 pounds)

Output Voltage: +5 VDC, 100 mV Peak-to-Peak Ripple

Output Current: 6 Amperes (Maximum)

Input Power: Universal 85 – 265 VAC, 47 – 440 Hz., 60 Watts

Ambient Temp. Range: 15 – 35 °C (59 – 95 °F)

Lake Shore Model 231 User’s Manual

Introduction

Figure 1-3. Typical Multiple Unit Case Physical Dimensions

Lake Shore Model 231 User’s Manual

Installation 2-

CHAPTER 2

INSTALLATION

2.0 GENERAL

This chapter covers inspection and unpacking in Paragraph 2.1, repackaging

for shipment in Paragraph 2.2, sensor installation recommendations in

Paragraph 2.3, sensor curve definitions in Paragraph 2.4, and power

connections in Paragraph 2.5.

2.1 INSPECTION AND UNPACKING

Inspect shipping containers for external damage. Make all claims for

damage (apparent or concealed) or partial loss of shipment in writing to

Lake Shore within 5 days from receipt of goods. If damage or loss is

apparent, please notify the shipping agent immediately.

Open the shipping containers. Use the packing list included with the system

to verify receipt of the instrument, sensor, accessories, and manual. Inspect

for damage. Inventory all components supplied before discarding any

shipping materials. If there is freight damage to the instrument, file proper

claims promptly with the carrier and insurance company and notify Lake

Shore. Notify Lake Shore immediately of any missing parts. Lake Shore

cannot be responsible for any missing parts unless notified within 60 days

of shipment. Refer to the standard Lake Shore Warranty on the A Page

(immediately behind the title page).

2.2 REPACKAGING FOR SHIPMENT

To return the Model 231 or accessories for repair or replacement, obtain a

Return Goods Authorization (RGA) number from Technical Service in the

United States, or from the authorized sales/service representative from

which the product was purchased. Instruments may not be accepted without

a RGA number. When returning an instrument for service, Lake Shore must

have the following information before attempting any repair.

1. Instrument model and serial number.

2. User name, company, address, and phone number.

3. Malfunction symptoms.

4. Description of system.

5. Returned Goods Authorization (RGA) number.

Repack the system in its original container (if available). Affix shipping labels

and FRAGILE warnings. Write RGA number on the outside of the container

or on the packing slip. If not available, consult Lake Shore for shipping and

packing instructions.

Lake Shore Model 231 User’s Manual

Installation

2.3 SENSOR INSTALLATION RECOMMENDATIONS

Refer to the Lake Shore Product Catalog for installation details and sensor

specifications. Call Lake Shore for copies of application notes or sensor

installation questions. Below are general recommendations on sensor

installation:

1. Do not ground the sensor.

2. Shield leads and connect shield wire to SHIELD on screw terminal

connector only. Do not connect shield at other end of cable.

3. Keep leads as short as possible.

4. Use twisted-pair wire. Use Lake Shore Duo-Twist™ wire (or equivalent)

for two-wire, or Quad-Twist™ wire (or equivalent) for four-wire

applications.

5. Thermally anchor lead wires.

2.3.1 Two-Lead versus Four-Lead Measurements

In two-lead measurement, the leads that measure sensor voltage also carry

the current. The voltage measured at the instrument is the sum of the

temperature sensor voltage and the IR voltage drop within the two current

leads. Since heat flow down the leads can be critical in a cryogenic

environment, wire of small diameter and significant resistance per foot is

preferred to minimize this heat flow. Consequently, a voltage drop within the

leads may exist.

Four-lead measurement confines current to one pair of leads and measures

sensor voltage with the other lead pair carrying no current.

2.3.1.1 Two-Lead Measurement

Sometimes system constraints dictate

two-lead measurement. Connect the

positive terminals (V+ and I+) together

and the negative terminals (V– and I–)

together at the instrument, then run

two leads to the sensor.

Expect some loss in accuracy; the voltage measured at the voltmeter equals

the sum of the sensor voltage and the voltage drop across the connecting

leads. The exact measurement error depends on sensor sensitivity and

variations resulting from changing temperature. For example, a 10  lead

resistance results in a 0.1 mV voltage error. The resultant temperature error

at liquid helium temperature is only 3 mK, but, because of the lower

sensitivity (dV/dT) of the diode at higher temperatures, it becomes 10 mK at

liquid nitrogen temperature.

I+

V+

I–

V–

Two-Lead

Measurements

Lake Shore Model 231 User’s Manual

Installation 2-

2.3.1.2 Four-Lead Measurement

All sensors, both two-lead and four-lead

devices, can be measured in a four-lead

configuration to eliminate the effects of lead

resistance. The exact point at which the

connecting leads solder to the two-lead

sensor normally results in a negligible

temperature uncertainty.

Always use four-lead measurement configuration

when a Series PT-100 Platinum Sensor is attached to the Model 231P.

2.3.2 Connecting Leads To The Sensor

Excessive heat flow through connecting leads to any temperature sensor

may differ the temperature between the active sensing element and the

sample to which the sensor mounts. This reflects as a real temperature

offset between what is measured and the true sample temperature.

Eliminate such temperature errors with proper selection and installation of

connecting leads.

To minimize heat flow through the leads, select leads of small diameter and

low thermal conductivity. Phosphor-bronze or Manganin wire is commonly

used in sizes 32 or 36 AWG. These wires have a fairly low thermal

conductivity, yet electrical resistance is not large enough to create

measurement problems.

Thermally anchor lead wires at several temperatures between room

temperature and cryogenic temperatures to guarantee no heat conduction

through the leads to the sensor.

2.3.3 Sensor Mounting

Before installing a diode sensor, identify

which lead is the anode and which is

the cathode. When viewed with the

base down and the leads towards the

observer, the anode is on the right and

the cathode is on the left. The Lake

Shore DT-470-SD silicon diode sensor

lead configuration is shown to the right.

For other sensors, read accompanying

literature or consult the manufacturer to positively identify sensor leads.

Lead identification should remain clear even after sensor installation. Record

the sensor serial number and location.

On the DT-470-SD, the base is the largest flat surface. It is sapphire with

gold metalization over a nickel buffer layer. The base is electrically isolated

from the sensing element and leads; make all thermal contact to the

I+

V+

I–

V–

Four-Lead

Diode

DT-470-SD

Diode Sensor Leads

AnodeCathode

Lake Shore Model 231 User’s Manual

Installation

sensor through the base. A thin braze joint around the sides of the SD

package electrically connect to the sensing element. Avoid contact to the

sides with any electrically conductive material.

When installing the sensor, make sure there are no electrical shorts or

current leakage paths between the leads or between the leads and ground.

If IMI-7031 varnish or epoxy is used, it may soften varnish-type lead

insulations so that high resistance shunts appear between wires if sufficient

time for curing is not allowed.

Slide Teflon® spaghetti tubing over bare leads when the possibility of

shorting exists. Avoid putting stress on the device leads and allow for

thermal contractions that occur during cooling which could fracture a solder

joint or lead if installed under tension at room temperature.

For temporary mounting in cold temperature applications, apply a thin layer

of Apiezon® N Grease between the sensor and sample to enhance thermal

contact under slight pressure. The preferred method for mounting the

DT-470-SD sensor is the Lake Shore CO Adapter.

CAUTION: Lake Shore will not warranty replace any device damaged by

user-designed clamps or solder mounting.

For semi-permanent mountings, use Stycast epoxy instead of Apiezon® N

Grease. NOTE: Do not apply Stycast epoxy over the DT-470-SD package —

sensor stress may shift the readings. In all cases, periodically inspect the

sensor mounting to verify good thermal contact to the mounting surface is

maintained.

For the Model 231P, Series PT-100 Platinum Sensors follow the same basic

procedures for diode type sensors. However, Platinum sensors have no lead

polarity, and some of the materials used at cold temperatures will not

tolerate the high-temperature range of the Platinum sensor.

2.3.4 Measurement Errors Due To AC Noise

Poorly shielded leads or improperly grounded measurement systems can

introduce AC noise into the sensor leads. In diode sensors, the AC noise

shifts the DC voltage measurement due to the diode non-linear

current/voltage characteristics. When this occurs, measured DC voltage is

too low and the corresponding temperature reading is high. The

measurement error can approach several tenths of a kelvin. To determine if

this problem exists, perform either procedure below.

1. Place a capacitor across the diode to shunt induced AC currents.

Capacitor size depends on the noise frequency. If noise is related to

power line frequency, use a 10 µF capacitor. If AC-coupled digital noise

is suspected (digital circuits or interfaces), use a 0.1 to 1 µF capacitor. In

either case, if measured DC voltage increases, there is induced noise in

the measurement system.

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Lakeshore 231, 231P, and 234 Temperature Transmitters User manual

Brand: Lakeshore

Model: 231, 231P, and 234 Temperature Transmitters

Type: User manual

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Lakeshore 231, 231P, and 234 Temperature Transmitters User manual

Lakeshore 231, 231P, and 234 Temperature Transmitters User manual

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