Fluke 2180A User Manual

For the benefit and convenience of its customers, Fluke

Corporation (Fluke) has reproduced this copy of a manual
which is no longer in production. This manual has not been
edited or updated since the revision date shown on the

lower left hand corner of the first page. Fluke will not be

liable for any claims, losses or damages of any kind
incurred by any user arising from use of this manual.

2180A

Digital

Thernnometer

P/N 489211

June 1978
REV. 2, 9/88

® 1988, John Fluke Mfg. Co., Inc., all rights reserved. Litho in U.S.A.

Instruction Manual

WARRANTY

Notwithstanding any provision of any agreement the following warranty is exclusive:

The JOHN FLUKE MFG. GO., INC., warrants each instrument it manufactures to be free from defects in material and
workmanship under normal use and service for the period of 1 -year from date of purchase. This warranty extends only to
the original purchaser. This warranty shall not apply to fuses, disposable batteries (rechargeable type batteries are
warranted for 90-days), or any product or parts which have been subject to misuse, neglect, accident, or abnormal
conditions of operations.

In the event of failure of a product covered bythis warranty, John Fluke Mfg. Co., Inc., will repair and calibrate an instrument
returned to an authorized Service Facility within 1 year of the original purchase; provided the warrantor’s examination
discloses to its satisfaction that the product was defective. The warrantor may, at its option, replace the product in lieu of
repair. With regard to any instrument returned within 1 year of the original purchase, said repairs or replacement will be
made without charge. If the failure has been caused by misuse, neglect, accident, or abnormal conditions of operations,
repairs will be billed at a nominal cost. In such case, an estimate will be submitted before work is started, if requested.

THE FOREGOING WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS, OR
ADEQUACY FOR ANY PARTICULAR PURPOSE OR USE. JOHN FLUKE MFG. CO., INC., SHALL NOT BE
LIABLE FOR ANY SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, WHETHER IN CONTRACT,
TORT, OR OTHERWISE.

If any failure occurs, the following steps should be taken:

1. Notify the JOHN FLUKE MFG. CO., INC., or nearest Service facility, giving full details of the difficulty, and include
the model number, type number, and serial number. On receipt of this information, service data, or shipping
instructions will be forwarded to you.

2. On receipt of the shipping instructions, forward the instrument, transportation prepaid. Repairs will be made at
the Service Facility and the instrument returned, transportation prepaid.

SHIPPING TO MANUFACTURER FOR REPAIR OR ADJUSTMENT

All shipments of JOHN FLUKE MFG. CO., INC., instruments should be made via United Parcel Service or “Best Way”*
prepaid. The instrument should be shipped in the original packing carton; or if it is not available, use any suitable container
that is rigid and of adequate size. If a substitute container is used, the instrument should be wrapped in paper and
surrounded with at least four inches of excelsior or similar shock-absorbing material.

CLAIM FOR DAMAGE IN SHIPMENT TO ORIGINAL PURCHASER

The Instrument should be thoroughly inspected immediately upon original delivery to purchaser. All material in the
container should be checked against the enclosed packing list. The manufacturer will not be responsible for shortages
against the packing sheet unless notified immediately. If the instrument is damaged in any way, a claim should be filed with
the carrier immediately. (To obtain a quotation to repair shipment damage, contact the nearest Fluke Technical Center.)
Final claim and negotiations with the carrier must be completed by the customer.

The JOHN FLUKE MFG. CO., INC, will be happy to answer all applications or use questions, which will enhance your use of
this Instrument. Please address your requests or correspondence to: JOHN FLUKE MFG. CO., INC., P.O. BOX C9090,
EVERETT, WASHINGTON 98206, ATTN: Sales Dept. For European Customers: Fluke (Holland) B.V., P.O. Box 2269,5600
CG, Eindhoven, The Netherlands.

♦For European customers. Air Freight prepaid.

John Fluke Mfg. Co., Inc., P.O. Box C9090, Everett, Washington 98206

Rev. 7/88

Table of Contents

SECTION TITLE PAGE

1 INTRODUCTION AND SPECIFICATIONS .............................................................. 1-1

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

1-3. DESCRIPTION ................................................................................................................ 1-1

1- 10. SPECIFICATIONS ........................................................................................................... l-I

2180A

2 OPERATING INSTRUCTIONS ................................................................................ 2-1

2- 1. INTRODUCTION ............................................................................................................ 2-1

2-3. SHIPPING INFORMATION ......................................................................................... 2-1

2-6. INPUT POWER ............................................................................................................... 2-1

2-10. INSTALLATION ............................................................................................................. 2-1

2-14. OPERATING FEATURES ............................................................................................. 2-2

2-16. OPERATING NOTES...................................................................................................... 2-4

2-18. Option Information ...................................................................................................... 2-4

2-20. Fuse Replacement ........................................................................................................ 2-4

2-22. RTD Installation........................................................................................................... 2-4

2-24. OPERATING DIRECTIONS.......................................................................................... 2-5

2- 26. Additional Features....................................................................................................... 2-5

3 THEORY OF OPERATION ...................................................................................... 3-1

3- 1. INTRODUCTION ............................................................................................................ 3-1

3-4. FUNCTIONAL DESCRIPTION..................................................................................... 3-1

3-9. CIRCUIT ANALYSIS...................................................................................................... 3-2

3-11. Digital Section............................................................................................................... 3-2

3- 16. Analog Section ............................................................................................................. 3-2

4 MAINTENANCE ....................................................................................................... 4-1

4- 1. INTRODUCTION ........................................................................................................... 4-1

4-3. SERVICE INFORMATION ........................................................................................... 4-1

4-6. GENERAL MAINTENANCE ........................................................................................ 4-1

4-7. Instrument Disassembly and Reassembly ................................................................. 4-1

4-9. Input Power ................................................................................................................... 4-2

4-11. Cleaning ......................................................................................................................... 4-2

4-13. Fuse Replacement ......................................................................................................... 4-2

4-15. Service Tools ................................................................................................................. 4-2

4-17. Static Discharge Precautions........................................................................................ 4-2

4-19. PERFORMANCE TEST ................................................................................................. 4-3

4-23. CALIBRATION ............................................................................................................... 4-4

4-25. Equipment Preparation ............................................................................................... 4-4

4-27. Reference Adjust ........................................................................................................... 4-4

4-29. Reference Adjust (+V) .................................................................................................. 4-4

4-31. Zero Adjust .................................................................................................................... 4-4

(Continued on Page ii)

i

2180A

TABLE OF CONTENTS, continued

SECTION

6

7

7A

8

TITLE

4-33. Resolution Adjustments ................................................................................................... 4-6

4-35. RTD Input Module Adjustment....................................................................................... 4-6

4-37. Lag Bath Construction ..................................................................................................... 4-6

4-39. SELECTED COMPONENT REPLACEMENT

4- 41. TROUBLESHOOTING..................................................................................................... 4-7

.............................................................

PAGE

4-7

LIST OF REPLACEABLE PARTS ............................................................................ 5-1

TABLE OF CONTENTS ................................................................................................ 5-1

5- 1. INTRODUCTION ............................................................................................................. 5-2

5-4. HOW TO OBTAIN PARTS.............................................................................................. 5-2

OPTION AND ACCESSORY INFORMATION

TABLE OF CONTENTS ................................................................................................ 6-1

..........................................................

6-1

GENERAL INFORMATION .................................................................................. 7-1

MANUAL STATUS INFORMATION .......................................................................... 7A-1

SCHEMATIC DIAGRAMS ......................................................................................... 8-1

TABLE OF CONTENTS ................................................................................................ 8-1

List of Tables

TABLE TITLE PAGE

1-1. 2180A Options and Accessories ......................................................................................................... 1-2

1-2. RTD Total Instrument Accuracy Specifications ............................................................................. 1-2

2180A

1-3. IPTS 68 Coefficients* ......................................................................................................................... 1-4

1- 4. General Specifications ........................................................................................................................ 1-4

2- 1. Controls, Indicators and Connectors ................................................................................................ 2-3

2-2. RTD Input Module Switch (SI)Settings .......................................................................................... 2-5

2- 3. RTD Input Module Switch Functions ............................................................................................. 2-6

3- 1. Mnemonics ........................................................................................................................................... 3-2

4- 1. Line Voltage Selection..............................................................

4-2. Recommended Test Equipment ......................................................................................................... 4-4

4-3. 2180A Performance Tests ................................................................................................................... 4-5

4-4. 2180A Troubleshooting ....................................................................................................................... 4-8

4-5. Test Point Identification ..................................................................................................................... 4-11/4-12

* For 2180A curve fit Linearizations

..........................................................

4-2

iii/iv

2180A

THIS PAGE INTENTIONALLY LEFT BLANK

List of Illustrations

FIGURE TITLE PAGE

Frontispiece Model 2180A Digital Thermometer ...................................................................................................... vi

2-1. Controls, Indicators and Connectors ................................................................................................. 2-2

2180A

2-2. RTD Connections ................................................................................................................................. 2-5

2- 3. RTD Input Module Access .................................................................................................................. 2-6

3- 1. 2180A Simplified Block Diagram ....................................................................................................... 3-1

3-2 Simplified Schematic Diagram - Digital ............................................................................................ 3-3

3- 3 Simplified Schematic Diagram - Analog ........................................................................................... 3-4

4- 1. Line Voltage Selection ......................................................................................................................... 4-2

4-2. Performance Test Connections ........................................................................................................... 4-3

4-3. Calibration Connections ..................................................................................................................... 4-5

4-4. Test Points and Measurement Cycle Waveforms ............................................................................. 4-9

2160A

Model 2180A Digital Thermometer

Table 1-2. RTD Total Instrument Accuracy Specifications (cont)

2180A

R
T
D

T
Y

P
E

R
E

TEMPERATURE RANGE

APPLICABLE PORTION OF

+/-DEGREES C
S
0
L

U

oc

OF

AT

CAL

L
T

1
0
N

100

ohm

390

.01° -200 to 0

0 to 204

.1°

-200 to 0 -327.9 to 32 .08 .10

Pt 0 to 750

-327.9 to 32
32 to 399.2

32 to 1382.2

.009 .055 .078
.009 .098

.08

100 .01° -200 to 0 -327.9 to 32 .040

ohm

3916

.1°

0 to 204

-200 to 0 -327.9 to 32

R 0 to 750

32 to 399.2

32 to 1382.2

.040 .13

.11
.10

MAXIMUM E

ERROR*

-^/-DEGREES F

90

DAYS

200

to

300

1

YR.

150

to

350

AT

CAL

.015 .100 .142

.139

.015

.11

.13

.23

.086

.32

.109

.13

.071

.171 .071

.12 .14 .17
.26

.34 .17

90

680

YR.

590

DAYS

to

860

950

.177

.16
.41

.156
.234

.252

.19
.57

.198
.309

.21 .24
.46 .62

1

to

100

ohm

392

R

100

ohm

617

Ni

10

.01°

.10

.010

.10

.010

-200 to 0
0 to 204

-200 to 0
0 to 750

-60 to 0

Oto 93

-327.9 to 32 .008 .055 .078
32 to 399.2

-327.9 to 32 .08 .01
32 to 1382.2

-76 to 32
32 to 199.4

-60 to 0 -76 to 32
0 to 177 32 to 350.6 .19

N/A

.009 .098 .139

.23 .32 .12 .41

.08

.157 .172

.129

.176

.129

.20

.19

.22

.014
.014 .177

.11

.12

.230

.199 .231

.21

.33 .35

.25

.33 .39

ohm

CU

.10

-75 to 0

-75 to 150

ohms

Oto 196.99

0 to 999.99 .05

Maximum error depends on the temperature measured and the resolution used. Of the four
temperature ranges presentd for each RTD, the first two represent .01° resolution. The
above maximum error numbers represent instrument errors only, and do not include the

RTD probe.

-103 to 32

-103 to 302

.005

.16
.16

.042
.22

.18
.20 .23

.059
.31

.27

.19

.27

ALL UNITS IN OHMS

.099

.16

.282
.317

.31
.35

.141
.252

.19
.57

.308
.359

.36
.44

.34
.41

1-3

2180A

Table 1-3. IPTS 68 Coefficients*

RTD TYPE

100 OHM

385 Pt
100 OHM

390 Pt

100 OHM

3916 Pt

100 OHM

NI

10 OHM

eu

RTD LINEARIZATION COEFFICIENTS

DIN 43760 TABLE

ALPHA = 0.0038994
DELTA = 1.494

A4 = -.0.265668^°''
C4 = -0.205984^°''

ALPHA = 0.003916
DELTA = 1.505

A4 = -.099668^°'
C4 =-0.192912^°''

ALPHA = 0.00617

RO = 9.042 OHM

R25 = 10.005 OHM

ALPHA = .004260

*SEE NBS MONOGRAPH 126

Table 1-4. General Specifications

DIMENSIONS

10.49 cm H X 20.45 cm W x 32.64 cm D
(4.13 in H X 8.05 in W X 12.85 in D)

WEIGHT

2.1 kg (4 lbs. 9 oz.)

OPERATING POWER
12V dc or 100, 120, 220, 240V ac ±10%, selectable

50 to 400 Hz; 8W typical, 14W max.

WARM-UP to RATED ACCURACY
5 minutes

STORAGE TEMPERATURE

-40°C to -H75°C
(Y2009 and Option 21X0A-004:0 to 40° C)

RELATIVE HUMIDITY

<80%, non-condensing, 0 to 50°C

SHOCK AND VIBRATION

Meets Ml L-T-28800 specifications

INPUT CONNECTION
4-wire to screw terminal block

INPUT IMPEDANCE
1000 Mohms at DC

STABILITY
±175 ppm in 90 days, ±200 ppm p:r \ :

ii

!

|.

1-4

Table 1-4. General Specifications (cont)

2180A

OPERATING TEMPERATURE
0 to 50°C

(Y2009: Oto 40°C)

ACCURACY vs WIRE LENGTH

No lead resistance error 4-wire RTD's if R2
adjustment on the RTD Input Module Is
used. Otherwise, 0.04°C/i2 resistance of any
one input lead if R2 is not adjusted.

DISPLAY

F or C, switch-selectable, 7-segment LEDs 1.1 cm

high

RESOLUTION

0.01 below 204 C for platinum RTD's, automatically
shifting to 0.1° above 204°C (93°C for nickel RTD's).

If readings are decreasing, shift Is at 77°C for platinum,

66°C for nickel.

MEASUREMENT METHOD
Dual slope integration, under microcomputer control.

100 ms integration period, three readings per second.
A/D Resolution is 100,000 counts at full-scale.

LINEARIZATION TECHNIQUES

Computer algorithm, 4th order curve fit.

TEMPERATURE COEFFICIENT
±15 ppm/°C from 25°C

RTD EXCITATION CURRENT

Nominal 0.5 mA.

COMMON MODE VOLTAGE
350V dc, 250V ac rms max.

NORMAL MODE REJECTION
>90 dB at DC, 50, 60, and 400 Hz ±0.1%.

RESPONSE TIME
1 second typical.

ZERO DRIFT
Automatic zero correction.

RTD TYPES
100S2 385 Pt (DIN), 390 Pt, 3916 Pt, 392 Pt,

100S2NÌ (DIN), lOnCU.

COMMON MODE REJECTION
>160 dB at DC, 50, 60, and 400 Hz ±0.1% with 100i2

unbalance at inputs.

SAFETY

Protection Class 1
Relates solely to insulation or grounding properties

defined in lEC 348.

VOLTAGE RANGE (CALIBRATION ONLY)

No annunciator or decimal point.

99999 mV full scale (switch S2 in AUTO), resolution 1 ¡A/
999990 mV full scale (switch S2 in .1), resolution 10 mV

1-5/1-6

2180A

THIS PAGE INTENTIONALLY LEFT BLANK

2180A

Section 1

Introduction & Specifications

: Si^TRODUCTION

1-2. The Model 2180A Digital Thermometer is a
portable, five digit RTD thermometer. Temperature
measurements are possible, depending on RTD type
employed, over a range of-219° C to +664° C (-394° F to
+1435°F) with 0.1° or .01° resolution. The instrument
features:

1. Front Panel switch selection of Fahrenheit or

Celsius readings.

2. Switch selectable RTD inputs.

3. Switch selectable input line voltage.

4. Dual slope measurement techniques.

5. Digital linearization of the RTD inputs.

1-3. DESCRIPTION

1-4. The instrument display features seven, high-

intensity, seven segment LEDs, and leading zero
suppression. Six of the LEDs are used to display numeric
data, with a minus sign for negative temperature readings.
The remaining LED displays the selected temperature
scale character (°F or °C).

1-6. Selection of the temperature scale for display is
made with a front panel pushbutton. The scale selected,
Celsius or Fahrenheit, is displayed as the last character in
the temperature reading (°C or ° F). A scale change can be
made at any time, and has no effect on calibration of the
instrument.

1-7. Options and accessories available for the 2180A are

listed in Table 1-1. More information concerning these
items is given in Section 6 of this manual. Option and
Accessory Information.

1-8. The measurement range of the 2180A Digital
Thermometer is determined by the type of RTD used as
the input device. RTD Types and total instrument
accuracy specifications are listed in Table 1-2.
Linearization of the RTD input is accomplished through
toggling of the input switch segments on the RTD Input
Module. Switch positions, numbers and applications are
printed on the removable module beside the switch.

1-9. Four input line voltages are available for switch
selection. Selection may be made for 100,120,220, or 240
volts ±10% as required to meet local conditions. Fre
quency may vary between 50 and 440 Hertz for all voltage
selections. Refer to Section 4 of this manual when
changing the selected input line voltage. Refer to Section
2, “Input Power” for 12 volt dc operation.

1-5. A four connection, screw-type terminal block is

provided on the removable Input PCB for RTD
connections. Input switch settings on this module will
determine the microcomputer program necessary to
linearize the desired RTD’s input. A precision, four-wire
resistance measurement of the RTD is routed through
this module to the thermometer’s input circuitry.

1-10. SPECIFICATIONS

1-11. Specifications for the 2180A Digital Thermometer

are given in Table 1-4. These specifications assume that
microcomputer type #2 has been installed in your instru
ment and at power-up the display reads “8002.2”

1-1

2180A

Table 1-1. 2180A Options and Accessories

ACCESSORY

Y2000
Y2009
Y2010

Y2014
Y2015
Y2016
Y2017
Y2020

Y2021

Y2022
Y2024

Y2026B
Y2031
Y2035
Y2037
Y2039

DESCRIPTION

Multipoint Selector, RTD
Battery Pack, 12V Rechargeable
Rack Panel PTI, single, A size (for Y2000)
Rack Panel PTI, single, C size (for 2180A and Y2002)
Rack Panel PTI, double, C size (for 2180A and Y2002)
7-inch Rack Adapter PTI, single, D size
7-inch Rack Adapter PTI, double, D size
Panel Mount PTI-DIN, C size (for 2180A and Y2002)
145 mm Panel Mount PTI, D size
Divider, Thermometer Calibrator

Power Cord, 3-way
Cable, Output Unit, RS-232-C
Input Module (for 2180A)
Thermal Paper (box of 10)
Pt 390 RTD Probe
Pt 392 Probe

Table 1-2. RTD Total Instrument Accuracy Specifications

TEMPERATURE RANGE

APPLICABLE PORTION OF +/-DEGREES C +/-DEGREES F

oc

-190 to 0

-190 too
0 to 750

,0lo

.10

R

0
L

U
L

T
1

1
0
N

R

T E

D S

T
Y

P

E

100
ohm 0 to 204

385

R

OF

-309.9 to 32
32 to 399.2

-309.9 to 32
32 to 1382.0

MAXIMUM ERROR*

AT

90 1

CAL DAYS

200

to

300

.043 .089

.132

.043

.12

.11
.11 .26

AT

YR. CAL

150 680 590

to

90

DAYS

to

YR.

350 860 950

.112

.076

.173

.14
.37

.161 .203

.076

.239

.21

.18
.18 .46

.314

.24
.62

1

to

1-2

Some semiconductors and custom IC’s can be
damaged by electrostatic discharge during
handling. This notice explains how you can
minimize the chances of destroying such devices
by:

1. Knowing that there is a problem.

2. Learning the guidelines for handling them.

3. Using the procedures, and packaging and
bench techniques that are recommended.

The Static Sensitive (S.S.) devices are identified in the Fluke technical manual parts list with the symbol

“(X)”

The following practices should be followed to minimize damage to S.S. devices.

1. MINIMIZE HANDLING

KEEP PARTS IN ORIGINAL CONTAINERS

UNTIL READY FOR USE.

3.

DISCHARGE PERSONAL STATIC BEFORE
HANDLING DEVICES. USE A HIGH RESIS

TANCE GROUNDING WRIST STRAP.

4. HANDLE S.S. DEVICES BY THE BODY

Page 1 of 2

5. USE STATIC SHIELDING CONTAINERS FOR
HANDLING AND TRANSPORT

a
o

iiiiiiHumir-wiiuuiiiiLimi

WHEN REMOVING PLUG-IN ASSEMBLIES,

8.

HANDLE ONLY BY NON-CONDUCTIVE
EDGES AND NEVER TOUCH OPEN EDGE
CONNECTOR EXCEPT AT STATIC-FREE
WORK STATION. PLACING SHORTING
STRIPS ON EDGE CONNECTOR HELPS TO
PROTECT INSTALLED SS DEVICES.

6. DO NOT SLIDE S.S. DEVICES OVER
ANY SURFACE

7. AVOID PLASTIC, VINYL AND STYROFOAM«

IN WORK AREA

PORTIONS REPRINTED
WITH PERMISSION FROM TEKTRONIX, INC.
AND GENERAL DYNAMICS, POMONA DIV.

HANDLE S.S. DEVICES ONLY AT A

9.
STATIC-FREE WORK STATION

10. ONLY ANTI-STATIC TYPE SOLDER­SUCKERS SHOULD BE USED.

11. ONLY GROUNDED TIP SOLDERING
IRONS SHOULD BE USED.

A complete line of static shielding bags and acces
sories is available from Fluke Parts Department,
Telephone [phone] or write to:

JOHN FLUKE MFG. CO., INC.

PARTS DEPT. M/S 86
9028 EVERGREEN WAY
EVERETT, WA 98204

® Dow Chemical

Page 2 of 2

J0089D-07U8604/SE EN Litho in U.SA

Rev. 1 MAR 86

2180A

Section 2

Operating Instructions

2-1. INTRODUCTION

2-2. This section of the manual contains information
regarding installation and operation of the 2180A Digital
Thermometer. It is recommended that the contents of this
section be read and understood before any attempt is made
to operate the instrument. Should any difficulties arise dur
ing operation, please contact your nearest Fluke Technical
Service Center, or John Fluke Mfg. Co., Inc. P.O. Box
C9090, Everett, WA 98206, Tel[phone]. A list of
Technical Service Centers is located in Section 7 of this
manual.

2-3. SHIPPING INFORMATION

2-4. The 2180A is packaged and shipped in a foam­packed container. Upon receipt of the instrument, a
thorough inspection should be made to reveal any
possible, shipping damage. Special instructions for
inspection and claims are included on the shipping
carton.

2-5. If reshipment of the instrument is necessary, the
original container should be used. If the original
container is not available, a new one can be obtained from
the John Fluke Mfg. Co., Inc. Please reference the
instrument model number when requesting a new
shipping container.

required for operation. Refer to Section 4 of this manual
for instructions on verifying or changing the input line
voltage switch settings.

2-8. The rear panel ac input connector is a three-prong,
U-ground connector which permits the instrument to be
connected, via the power cord, to the applicable line
voltage. The offset prong on this connector is attached to
the 2180A power supply, and should be connected
through the power cord to a high quality earth ground.

2-9. The 2180A will also operate on 12V dc power. A

rear panel terminal block, with screw tightened
connections, (TBl), allows for ease of attachment. Actual

input voltage may vary from 11 to 15V dc; most 12V dc
power supplies capable of supplying lA (e.g., a car
battery) can be utilized.

2-10. INSTALLATION

2-11. The 2180A is contained in a special molded plastic
instrument case. Other associated accessories used with
the 2180A will be packaged in similar PTI (Portable Test
Instrument) cases varying only in size. The cases are, in all
other respects, compatible and can be stacked vertically
and latched together to form miniature portable test
systems. Instrument stacks should be limited to a total of

40 pounds.

2-6. INPUT POWER

2-7. The 2180A will operate at any of four switch
selected input line voltages, all of which operate at
frequencies from 50 to 440 Hertz. Before connecting the
2180A to the local ac line, verify that the present setting of
the instrument matches the local line voltage. A decal on
the instrument rear panel defines the original setting

2-12. Use the following procedure when attaching PTI
cases to each other:

1. For the top case, pull out latches found on

either side of the instrument.

2. Nestle top and bottom cases together.

3. Push latches in to secure units together.

2-1

2180A

2-13. Prepare the 2180A for operation by plugging the
input line power cord into the applicable power source or
connecting the external input connector to an external

12V dc source.

2-14. OPERATING FEATURES

2-15. The location of the 2180A controls, indicators,
and connectors is shown and described in Figure 2-1 and
Table 2-1 respectively.

2-2

Figure 2-1. Controls, Indicators and Connectors

Table 2-1. Controls, Indicators and Connectors

2180A

REF

1

2

3

4

5

6

NAME FUNCTION

Digital Display

Temperature Scale Indicator

Power Switch

SCALE

LIMIT and FUNCTION

LIMIT EXCEEDED

Displays a five digit readout of the measured input temperature. Leading
zero suppression and a variable position decimal point are included. A
minus sign is displayed for negative temperature measurements. Flashes

when overranged.

Displays the temperature scale represented by the digital display data:

Or» Oc

C or F.

Push on/Push off.

Selects the temperature scale for display: °C or °F.

Part of the —006 Limits Option. When installed, the thumbwheels may

be set to a four digit LIMIT value (+ or —). The FUNCTION thumbwheel
can then be set to define the limit value and signal (LIMIT EXCEEDED)
when the displayed temperature has exceeded the limit value (>, <). Dis
play will read the difference between the thumbwheel setting and the
actual temperature when (a) is set in FUNCTION. Set FUNCTION thumb
wheel for storage of maximum (T ) or minimum (J_) measured since
last initializing (no limit value settings).

Part of the —006 Limits Option. Indicator illuminates when the preset
limits have been exceeded.

7

8

CALIBRATION COVER Sliding cover for calibration adjustments.

INITIALIZE MAX/MIN Part of the —006 Limits Option. Resets the previous maximum and

minimum readings stored by the microcomputer.

9

DIGITAL OUTPUT

Connector for the ASCII coded data for the Output Unit, if 21XOA-002 is installed.
Connector for the IEEE-488 if 21X0A-004 is installed (instead of 21X0A-002).

ANALOG OUTPUT Banana jack connector for an Analog Output (1 mV per degree), if 21XOA-002 Is

9a

installed. (Only used with 21X0A-002.)

10

RTD INPUT MODULE

Removable module houses RTD Input connections and type selection

switch.

11

12

13

F2

ACCESSORY CONNECTOR Cable connector for accessory bus connection from accessory units.

FI

External 12V dc input fuse (3/4A MDL slo-blo).

Input line power fuse 1/8A (100 or 120 VAC) 1/16A (220 or 240 VAC).
MDL (slo-blo).

14 LIMITS When the Limits Option is installed, it provides contact closure when

the set limit has been exceeded.

±12 VDC

1b

Input terminals for the external 12V dc power source.

16

LINE VOLTAGE

CONNECTOR

Input connector for the input line voltage.

2-3

2180 A

2-16. OPERATING NOTES

2-17. The following paragraphs describe various
conditions that could affect operation of the
thermometer. The operator should familiarize himself
with these conditions prior to operating the 2180A.

2-18. Option Information

2-19. Supplementary operating instructions are
necessary when operating the 2180A equipped with one of
the available options. Detailed information regarding the
operation of each available option is given in Section 6 of
this manual, Option and Accessory Inforamtion.

2-20. Fuse Replacement

2-21. The ac line input and external dc input are
individually fuse protected. Both fuses are readily
accessible on the outside of the rear panel. The ac line
input fuse (FI) should be replaced with a 1 /8A MDL(slo­blo) fuse if either 100 or 120 volt operation has been
selected. Usea 1/16A MDL(slo-blo) replacement for 220
or 240 volt operation. The external dc input (F2) requires
a 3/4A MDL (slo-blo) fuse for a replacement.

CAUTION

Remove the power connector from the 2180A
before changing fuses.

4. On the Input Module, toggle the RTD SekOi

Switch (S1) to obtain the desired RTD type, see TD

2-2.

NOTE

The RTD Input Module may be printed with

microcomputer Type 41 selector switch set

tings. Refer to Table 2-2 when changing RTD
types.

5. Slide the Input Module, RTD lines attache
back into the 2180A securely.

NOTE

Refer to Section 6 of this manual or applicable
accessory manuals for instructions on the
operation of any installed options or
connected accessories.

6. Set POWER switch to ON.

7. Expose the RTD to a temperature within the
RTD’s specified range (see Specifications in Section

1

).

2-22. RTD Installation

2-23. Use the following procedure when installing an

RTD and conducting temperature measurements:

1. Set POWER switch to OFF.

2. Remove the RTD Input Module from the
instrument (rear panel).

3. Route the selected RTD lines through the Input
Module’s rear access port, and connect them to the
input terminals; depending on the type of RTD,
connections may involve 2, 3, or 4 wires. Refer to
Figure 2-2 as a reference when connecting RTD

lines to the Input Module (TBl). Lines of the same
color usually go to the same polarity connections
(T-V and TS, or -V and -S). Refer to instructions
included with the RTD for specific connection
directions.

NOTE

When 2- or 3~wire RTDs are used, there is

some error created due to the RTD excitation

current in the Sense (S) wire leads. To

minimize this error. The user should (when
possible) use the 4-wire RTD connection as
show in Figure 2-2.

8. The RTD temperature, in the scale selected, is
displayed on the front panel.

NOTE

R2 on the 2180A is adjusted at the factory
with a 100 ohm input resistance. If the 2180A
is used with a 100 ohm 385 Pt RTD probe
meeting DIN standard 443760, then the R2
adjustment in the following paragraph may be
ignored.

9. Adjust R2 on the RTD Input Module to com
pensate for variations in lead resistance and in RTD
probe Ro values. Refer to Section 4 for RTD input
module adjustment procedures. This adjustnieni
must be performed when an RTD probe is initially
installed and whenever the leads or the RTD are
changed.

NOTE

The RTD adjustment can be used to calibrate
the 2180A and the probe near a specific
temperature. Adjust R2 for compatibility
between the 2180A and a customer supplied
temperature reference.

2-4

2180A

2-24. OPERATING DIRECTIONS

2-25. Operate the 2180A Thermometer using the
following procedure:

1. Verify the instrument has the correct RTD

connected.

2. Connect the input line cord to the applicable
power source.

3. Select the temperature scale desired for display
by pressing the Front Panel SCALE switch (in for
°C, and out for °F).

4. Set POWER switch to ON.

2-26. Additional Features

2-27. The following paragraphs describe how the 2180A
may be used to measure voltage or resistance. In both
cases, the RTD will be replaced with a length of standard
electrical wire. To connect the standard wire to the RTD
Input Module, use steps 1-3 of the RTD Installation
procedure, ignoring all reference to the RTD.

4-WIRE CONNECTIONS

+V
+S

-V

-S

3-WIRE CONNECTIONS

+V

+S

-V

-s

2-WIRE CONNECTIONS

+V

+S

2-28. HOW TO MEASURE VOLTAGE
2-29. The 2180A can be used to measure positive

voltages only up to +100 mV or +1V maximum in two
ranges, with 1 )uV or 10 /zV resolution respectively. To
obtain the desired range, refer to the following steps and
Figure 2-3.

Table 2-2. RTD Input Module Switch Settings

TYPE

* = OHMS

** = PLATINUM
EXAMPLE: To select a switch setting of 5, position the RTD selector switch (1) as shown:

DISPLAY

READING

pP

AT TURN

ON

2

8002.2

0

100*
385**

12 4 8

1

100*
390**

RTD SELECTOR SWITCH (SI) SETTINGS

2

100*

3916**

3

100*
392**

□ [zz:

4

100*

N1

1+4 + 5

Figure 2-2. RTD Connections

10*

cu

5

6

—

7

—

-V

-S

8

OHM

9

CAL

2-5

2180A

Table 2-3. RTD Input Module Switch Functions

SWITCH

NO.

SI

S2

S3

SWITCH

POSITION

0-5

6,7

8

9

.1

AUTO

Scan

Man

SWITCH FUNCTIONS

Programs the microcomputer (juc) for each RTD probe type (See Table 2-2.)

NOT USED

''RESISTANCE'', programs the ¡jlc to read ohms.

"CAL'', programs the ¡ic to read juV (bypasses the linearization program).

Causes the analog to digital converter circuitry (A/D) to have jjlV input sensitivity and

displays temperature to 0.1° resolution only.

Causes the A/D to automatically change from .01° to 0.1° resolution for overrange or

0.1° to .01° resolution for underrange.

Not Used

MUST BE LEFT IN THIS POSITION DURING NORMAL OPERATION.

2-6

2180A

NOTE

The decimal point and temperature scale
indicator should be ignored during
the following steps, the user must be aware of
the selected range.

2-30. 100 millivolt Range

1. Install lead wire to the RTD Input Module,
refer to RTD Installation procedures, steps 1-3 (this
section).

2. Set RTD Input Module switches, S1 to position
9 and S2 to AUTO.

3. Replace RTD Input Module and turn 2180A
on.

4. The 2180A is now ready to measure positive
voltages up to +100 mV.

2-31. 1 Volt Range

1. Install lead wire to the RTD Input Module,
refer to RTD Installation procedures, steps 1-3 (this
section).

2. Set RTD Input Module switches, S1 to position
9 and S2 to .1°.

3. Replace RTD Input Module and turn 2180A
on.

4. The 2180A is now ready to measure positive
voltages up to +1V.

excitation M).5 mA). To set up the 2180A as a resistance
measurement device, refer to the following steps and
Figure 2-3.

NOTE

The temperature scale indicator (^Cj'^F)

should be ignored during the following steps.

2-34. Resistance Measurements

1. Install lead wires to the RTD Input Module,

refer to RTD Installation procedure, steps 1-3.

2. Set RTD Input Module switches, S1 to position
8 and S2 to .1°.

3. Connect a known resistance, less than 1 kfl, to
the wires connected to the RTD Input Module, and
use the following steps to compensate for lead
resistance.

4. Replace RTD Input Module and turn 2180A
on.

5. Adjust R2 through the rear panel of the RTD’s
Input Module until the 2180A’s display reads the
same value as the known resistance.

6. Remove the known resistance, the 2180A is
now calibrated and ready to measure positive
resistances up to 999.9il.

2-32. HOW TO MEASURE RESISTANCE
2-33. The 2180A can be used to measure positive

resistances up to 999.9il with 10 mil resolution (RTD

NOTE

For measuring resistances of less than 196Ci,
switch S2 on the RTD Input Module should
be set to the A UTO position.

2-7Z2-8

2180A

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2180A

Section 3

Theory of Operation

3-1. INTRODUCTION

3-2. This section of the manual contains an overall
functional description and a brief circuit analysis of the
2180A Digital Thermometer. Simplified circuit diagrams
are provided, as necessary, to supplement the text.
Detailed schematics are given in Section 8 of this manual.

3-3. The Model 2180A is a single point RTD Digital
Thermometer with 0.1° and .01° resolution for either
degrees F or C. This instrument features dual slope A/D
conversion, microcomputer control logic, and a 5-digit
display with temperature scale indicator. Various RTD
types can be used over a temperature range of -394° F to

1435°F (-219°C to 664°C). Refer to Figure 3-1 for the
following functional description. Mnemonic definitions
are provided in Table 3-1.

3-4. FUNCTIONAL DESCRIPTION

3-5. The Model 2180A executes a continuous series of
measurement cycles. These cycles, controlled entirely by a
microcomputer, include three major periods: the Auto­Zero, the Integrate, and the Read periods. During each
period, digital controls are applied to the analog section
of a dual slope converter. The converter in turn generates
a compare output. The configuration of the analog
section during each phase of the measurement cycle is
established by the condition of microcomputer controlled

FET switches.

3-6. The measurement cycle begins with the Auto-Zero
period. During this period, the input to the Buffer
Amplifier is connected to ground through an FET switch
and the accumulated dc offset voltages present in the
analog section are sampled and held by the Auto-Zero
capacitor. This voltage is used later in the measurement
cycle to cancel measurement errors introduced by offset
voltages in the analog circuitry. The final measurement is

therefore proportional to the RTD probe output voltage
and does not include offset errors.

3-7. During the Integrate period, the RTD input voltage
read across the RTD, is applied to the integrator. The
algebraic sum of the AZ and RTD input voltages is
integrated over a 100 ms period. At the end of this period,
the RTD input voltage is removed from the integrator,
and the Read period is started.

3-8. A reference voltage is applied to the integrator
during the Read period, causing the integrator capacitor
to be discharged at a linear rate. When the integrator
output reaches zero, a compare signal is generated to end
the Read period. The duration of the Read period is
translated by the microcomputer, to provide a digital
indication of the RTD temperature.

RTD

DUAL SLOPE

ANALOG CIRCUIT

N

<

DATA

i UJ

cc

<
a.

O

o w

^ i k i

5

LU
QC

MICROCOMPUTER

CONTROL & LINEARIZATION

DISPLAY

Figure 3-1. 2180A Simplified Block Diagram

3-1

2180A

Table 3-1. Mnemonics

ANALOG COM
AZ

CM
DATA
DCLK
DE+
DE­DIGITAL COM
D.P./NEG

INT 1
LINEAR

WRT
WRT ADR

X10

X100

A2

+SENSE

-SENSE

+Vm

-V

Measurement common
Auto-Zero

Compare input to the microcomputer
Data on bus
Data clock
Positive read command
Negative read command
—15V with respect to Analog Com

Drives decimal point, depending on reading and resolution
Causes the unknown voltage to be integrated
Used to command the microcomputer to display linear counts

Write
Write address, signals that an address is being transmitted
Selects a buffer gain of X10 (0.1° resolution)
Selects a buffer gain of X100 (0.01° resolution)

Hold command

Voltage sense wires from RTD - no current flows In these wires
Voltage sense wires from RTD - no current flows in these wires
An intermediate voltage - not used directly
Current return

3-9. CIRCUIT ANALYSIS

3-10. Circuit analysis of the 2180A is discussed in two
sections: digital and analog. The digital section is covered
first; particular attention is paid to digital control of the
analog section. The analysis of the analog section covers
the analog measurement circuitry and the 2180A power
supply.

3-11. Digital Section

3-12. The digital section of the 2180A consists of a
single-chip microcomputer with a self-contained,
programmed, read only memory (U9), a hex CMOS open
drain buffer (U13), and an LED display. This section,
shown in Figure 3-2, will provide the following functions:

1. Conversion of the non-linear RTD probe
voltage, as measured by the analog section, into a
linear digital display.

2. Control of the analog section.

3. Control of all accessories on the accessory bus.

type of RTD. One of the seven operating programs is
selected for the RTD type by setting S1 on the RTD Input

Module. A table showing RTD switch setting numbers
and corresponding RTD types is printed on the RTD
Input Module PCB.

3-14. Measurement data is continuously strobed out of
the microcomputer in decoded-seven-segment, bit­parallel, character-serial format. This data is then sent to
the LED display.

3-15. The total measurement cycle takes 300 ms. The
cycle consists of the following periods:

1. Auto-Zero period (100 to 200 ms).

2. Integrate period (100 ms). A 1 ms nominal hold
signal is inserted at the beginning and end of the
Integrate period to accomodate settling times in the
analog section.

3. Read period (variable 0 to 100 ms).

3-16. Analog Section

3-13. The microcomputer (U9) contains all of the 2180 A
programming, control logic, and linearizing capability. It
also provides all signals necessary to update the display.

Linearization of the RTD signal is accomplished by using
a piece-wise, 4th order, curve-fit approximation for each

3-2

3-17. ANALOG MEASUREMENT CIRCUIT

3-18. The analog measurement circuitry consists of an
RTD input circuit, two voltage reference circuits, a
ground sense amplifier, a buffer amplifier, a dual slope

2180A

CO

I

CJ

CO

h-

LU

AOU/DOU

OPTION

ri__rt

05 04 015 Oil

Q22

(^©©©©

021 ( k

Q7 k

016 k

017 ( k

Q10{ k

LIMITS

OPTION

-<U^

AZ

INTI

A2

X10

XI00

DE-

MICRO

COMPUTER

U9

T ^

>
<

014 (k

013 ( k

Q9 k

Figure 3-2. Simplified Schematic — Digital

A/D Converter (integrator, gain stage, and comparator),

and a combination of FET switches. Refer to Figure 3-3
in conjunction with the following individual circuit
descriptions. All FET switches will be shown in their open
state; they are closed during measurement cycle
commands from the 2180A’s digital section.

3-19. The RTD Input circuit comprises the RTD probe,
the RTD Input Module, and a low pass filter on the Input

Module’s PCB. Source current flows through a series

combination of the RTD probe, R2 (RTD Input

Module), and R1 (Main PCB). The voltage sensed across
the RTD is routed through the Input Module, and onto
the Main PCB. The TSense line (always a positive
voltage) is then applied to the low pass filter.

DE+

f^o

U16

3-20. The ground sense amplifier (Q20, U7 and
associated circuitry) maintains the -Sense line at
measurement ground. This amplifier compensates for
noise and offsets on the -V and -Sense lines.

3-21. To achieve switching between 0.01° and .1°
resolution, the buffer gain is shifted by a factor of ten. For

0.01° resolution, FET switch Q17 is on, and a reference
voltage of-100 mV is applied to the buffer (Q19, U5). The
buffer gain is set to 100. For 0.1° resolution, FET switch
Q16 is on, and a reference voltage of -1 .OOV is applied and
the buffer gain is 10.

3-22. The first voltage reference consists of a resistor
network supplied by an accurate 6.2V dc reference
voltage. The resistive divider network is set to provide 200
mV to Q14, lOOmVtoQ15, l.OVtoQl l,and2.0VtoQlO.

MHz

3-3

Ca)

»

CO

I

CO

IVO

00

о

>

CO

i’

■ö
ü

CO

о

0

1

>
3

&

2180A

When 0.01° resolution is in use, Q12 will allow reference
capacitor C19 to attain a -100 mV charge. For 0.1°
resolution, Q8 will allow C20 to charge to ° l.OV. Either
reference capacitor will be placed at the -Sense level
during Auto-Zero. Recovery deintegrate is applied to
QIO and Q14.

3-23. A second voltage reference (U15-6) provides an
accurate 6.2V across the series combination of R1 (Main
Thermometer PCB), R2 (RTD Input PCB), and the

RTD. This voltage therefore provides the source (+V)
voltage for the RTD.

3-24. The Buffer, Integrator, Gain Stage, and

Comparator Amplifiers combine to perform the analog
functions of the Integrate, Read, and Auto-Zero periods.
The Buffer is used to provide integrator inputs during all
three periods. The Integrator integrates the Buffer output
voltage during the Integrate and Read periods and, in
combination with the Gain Stage, functions as a closed­loop amplifier during the Auto-Zero period.

3-25. An Auto-Zero period is commanded during the
first phase of each measurement cycle. During this time,
five auto-zero switches (Q4, Q5, Q11, Q15, and Q22) are
closed by the microcomputer. Three of the switches (Q11,
Q15, and Q22) charge the reference capacitors to +100
mV on Cl9 and +1.0V on C20. Closing switch Q4
connects the Integrator and Gain Stage into a closed-loop
configuration. This action also allows the Auto-Zero
capacitor (Cl2) to charge to a value proportional to the
algebraic sum of all the offset voltages in the Buffer,

Integrator and Gain Stage. At the end of the Auto-Zero
period, switches Q4, Q5, Q11, Q15, and Q22 are opened.
The reference capacitors (Cl9 and C20) and the Auto­Zero capacitor retain their charges for later use in the

measurement cycle.

Read mode is enabled. Similarly, a negative Read mode is
enabled when a negative input is sensed.

3-28. When the positive Read mode is commanded,
FET switches Q13 and Q9 are closed. If 0.1° resolution is
in effect, Q8 will place the positive side of reference
capacitor C20 at ground. With 0.01° resolution in effect,
Q12 will place the positive side of reference capacitor Cl 9
at ground. Reference capacitors C20 and Cl9 will then
apply either -1 .OV or -100 mV, respectively, to the Buffer
input.

3-29. When the negative Read mode is commanded,
switches QIO and Q14 are closed; Q9 and Q13 are open.
With .01° resolution selected, approximately +200 mV
will be applied to the positive side of reference capacitor
Cl9. The algebraic sum of the voltage at the Buffer input
will then be +100 mV. When 0.1° resolution is selected,
approximately +2.0V will be applied to the positive side
of reference capacitor C20. Buffer input voltage will then
be +1.0V (only during recover deintegrate).

3-30. After a 1 ms settling time, switch Q7 closes and the
Buffer output voltage is applied to the Integrator input.
The integrator capacitor now begins to discharge at a
linear rate (determined by the reference voltage). This
discharge continues until the integrator voltage reaches
the comparator trip point, which is referenced to the
voltage on the Auto-Zero capacitor. When this level is
reached, the comparator changes state, commanding the
microcomputer to terminate the Read period. To
facilitate auto-zero, the microcomputer then calls a
reference voltage opposite in polarity to the one
previously used (DE- or DE+). When the integrator
reaches the trip point, the microcomputer immediately
begins the Auto-Zero period.

3-26. The Integrate period (see Figure 4-4) starts on the
leading edge of the integrate command from the
microcomputer; switch Q21 is closed and switch Q7 is

opened. The RTD input voltage is applied through switch
Q21 to the Buffer input. After a 1 ms settling period,
switch Q7 closes, and the Buffer output is applied to the

Integrator for 100 ms. As the integrator capacitor C2
charges, the Integrator drives the comparator, through
the gain stage to +5V dc which indicates that the charge
on C2 is more negative than the Auto-Zero Reference
Cl2. At the end of the Integrate period, the integrate
capacitor is charged to a level and polarity proportional
to the RTD voltage, and switches Q21 and Q7 return to
the open state.

3-27. The Read period starts at the end of the Integrate
period. Depending upon the input polarity sensed by the
comparator during the Integrate period, one of two Read
modes is enabled if a positive input is sensed, a positive

3-31. Offset voltages present during the Integrate and
Read periods are cancelled by offset voltages that were
sampled and held during the Auto-Zero period.

3-32. POWER SUPPLY

3-33. The 2190A Power Supply consists of a DC to DC

Converter and regulating circuitry. AC inputs are made
via the input power cord, line fuse, and power
transformer/rectifier. External +12V dc inputs can also
be made directly to the DC to DC Converter circuitry via
line TBl (see Main PCB schematic. Section 8). The
function of the power supply is to provide +5V, +5V
unregulated, +15V, and -15V dc operating voltages for
the 2180A circuitry. The power supply can be driven from
ac line or 12V dc external source. The DC to DC
conversion and voltage regulation is accomplished using
conventional power supply design techniques.

3-5/3-6

2180A

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