Yokogawa EJA110E Bedienungsanleitung PDF herunterladen (Seite 40)

<8. Maintenance>

8-1

IM 01C25B01-01E

8. Maintenance

8.1 Overview

WARNING

Since the accumulated process uid may be

toxic or otherwise harmful, take appropriate care

to avoid contact with the body or inhalation of

vapors when draining condensate or venting gas

from the transmitter pressure-detector section

and even after dismounting the instrument from

the process line for maintenance.

Maintenance of the transmitter is easy due to its

modular construction. This chapter describes the

procedures for calibration, adjustment, and the

disassembly and reassembly procedures required

for component replacement.

Transmitters are precision instruments. Please

carefully and thoroughly read the following sections

for information on how to properly handle them

while performing maintenance.

IMPORTANT

• As a rule, maintenance of this transmitter

should be done in a shop that has all the

necessary tools.

• The CPU assembly contains sensitive parts

that can be damaged by static electricity.

Take precautions such as using a grounded

wrist strap when handling electronic parts or

touching the board circuit patterns. Also be

sure to place the removed CPU assembly

into a bag with an antistatic coating.

8.2 Calibration Instruments

Selection

Table 8.1 lists the instruments that can be used

to calibrate a transmitter. When selecting an

instrument, consider the required accuracy level.

Exercise care when handling these instruments to

ensure they maintain the specied accuracy.

8.3 Calibration

Use the procedure below to check instrument

operation and accuracy during periodic

maintenance or troubleshooting.

1) Connect the instruments as shown in gure 8.1

and warm up the instruments for at least ve

minutes (ten minutes for EJ310.)

IMPORTANT

• To adjust the transmitter for highest

accuracy, make adjustments with the

power supply voltage and load resistance

including leadwire resistances set close to

the conditions under which the transmitter is

installed.

• If the measurement range 0% point is

0 kPa or shifted in the positive direction

(suppressed zero), the reference pressure

should be applied as shown in the gure.

If the measurement range 0% point is shifted

in the negative direction (elevated zero), the

reference pressure should be applied using

a vacuum pump.

2) Apply reference pressures of 0%, 50%,

and 100% of the measurement range to the

transmitter. Calculate the errors (differences

between digital voltmeter readings and

reference pressures) as the pressure is

increased from 0% to 100% and is decreased

from 100% to 0%, and conrm that the errors

are within the required accuracy.

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