Campbell Scientific CR10 CR10 Measurement and Control - Page 87

SECTION

7.

MEASU

REI,iIENT

PROGRAMMING

EXAM

PLES

FTGURE

7.3-1.

CRl0TCR Mounted on the

CRl0 Wiring

Panel

7.3

THERMOCOUPLE TEMPERATURES

USING

THE OPTIONAL

CR1OTCR

TO

MEASURE

THE

REFERENCE

TEMPERATURE

The CRlOTCR Thermocouple Reference

is

a

temperature

reterence for thermocouples

measured with the

CR10

Measurement and

Control

Module.

When

installed,

the CRlOTCR

lies between the two

analog

input

terminalstrips

of

the

CRl0

Wiring

Panel (see Figure 7.3-1).

The

CRlOTCB circuitry,

measurement, and

specifications are equivalent

to

Campbell

Scientific's

1

07

Temperature

Probe.

The

CRl0TCR

is

connected

to

single-ended

channel

1

(1H), excitation channel

3

(E3) and

analog ground

(AG).

lt is measured with

lnstruction

11

which excites

the

probe with a

2.5VAC

excitation,

makes

a

single ended

measurement and calculates

temperature

("C).

Five ditferential

thermocouples are

measured

with Instruction

14.

(Refer to

the

CRloTCR

Manualfor

instructions

on

measuring a

thermocouple

in

differential

channel

1.)

The

temperature

('C)

of

the CRlOTCR

is stored

in

Input Location

1

and the thermocouple

temperatures

('C)

in Locations 2-6.

PROGRAM

Temp

107 Probe

Rep

lN Chan

Excite

all

reps w/EXchan

3

Loc

[:REF

TEMP

]

Mult

Offset

Thermocouple Temp

(DIFF)

Reps

7.5

mV

60

Hz rejection Range

lN

Chan

Type

T

(Copper-Constantan)

Ref

Temp Loc

REF TEMP

Loc

[:TC

#1

I

Mult

Offset

7.4

THERMOCOUPLE TEMPERATURES

USING

AN

EXTERNAL

REFERENCE

JUNCTION

When a

number of

thermocouple

measurements

are

made at some distance from

the

CR10, it

is

often better

to

use

a

reference

junction

box located

at the

site

rather

than

use

the

CR1OTCR

Thermocouple

Reference.

Use of

the

external

reference

junction

reduces

the

required length

of

expensive thermocouple

wire as

regular

copper

wire

can be

used between the

junction

box

(J-box)

and

CR10.

In

addition,

if

the

temperature

gradient

between the

J-box

and the

thermocouple

measurement

junction

is

smaller

than the gradient

between the CR10 and

the

measurement

junction,

thermocouple

accuracy is improved.

01:

P11

01:

1

02:

1

03:

3

O4:

1

05:

1

06:

0

02:

P14

01:

5

Q2:

22

03:

2

04:.

1

05:

1

06:

2

07;

1

08:

0

7-3

Campbell Scientific CR10 CR10 Measurement and Control - Page 87

Thermocouple Temperatures, The Optional, Temperature, External, Junction

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