Edgetech 2000 Series - Locating Troubles and Test Points

66 pages

To Next Page

To Next Page

To Previous Page

To Previous Page

Loading...

1

-·.

·;

·

Model

2000

Series

DewPrime

Dew Point Hygrometers

----------Troubleshooting

and

Repair----------

6.1 LOCATING TROUBLE

n some cases of faulty

in.strument

operation,

the

source of trouble will be

immediately

apparent.

TP3

Can be

used

to measure Sensor current

by

measuring the voltage between TP3

and

TPAGND

(analog ground) and dividing

by

··

·-:-

·

In

others,

this will not be the case

since

a

given

symptom may often be

due

to any one of several

causes.

In

locating

and eHminaring

such

faults, two methods

are

recommended:

1. When trouble arises, a number of simple

prelimi-

nary checks, listed

in

Table

6-1, should be

made

before proceeding with more elaborate

tests

.

These

checks, which can be performed without

disturbing

any components of the system, are designed

to

detect or correct those troubles most likely to

occur.

2.

If

the

trouble is not located or remedied by the

preliminary checks,

a

serie

s

of tests, descn'bed

in

Table 6-2, can be used to isolate the fiwlt to one

of

the major sections of the system. When this is

done,

the faulty section can then be

replaced

or

checked

systematically

to locate

th

e

particular component

causing

trouble

.

6.2 TEST

POINTS

The following test points are available on the main

PC

board:

TPl The

SJJDlming

point of the

main

servo

amplifier.

TP2 Output of servo

amplifier

.

This

voltage

ultimately controls the Sensor

currem

and

is also the voltage represemed by

the

CONI'ROL

LEDs.

TP4

TPS

TP6

TP7

TP8,9

TPIO

TPll

TP12

TPVCC

TPAGND

TPDGND

0.1.

TP3 and TP4 represent both sides of

the

Sensor.

Represents the output of the PRT

amplifier

and is approximately

lOV/lOOOC

.

Output

ofD/A

converter that generates

the

balance

voltage.

·

The

shifted balance voltage as presented

to

the

SlJDlming

point.

The

differential

inputs of the PRT

ampli-

fier.

The junction between the +ISV and

the

phototransistor

s

in

the Sensor

The junction

betwee

n

the

-lSV

and

the

phototransistor

s

in

the

Sensor

The voltage generated by the

thickness

potentiometer (R64)

.

The +SV

supply.

Analog

ground.

Digital ground.

6-1