Maintenance; Overview; Calibration Instruments Selection; Calibration - YOKOGAWA DpharpEJX vigilantplant EJX110 User Manual

8.

MAINTENANCE

8.1 Overview

WARNING
Since the accumulated process fluid 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 instru-
ment 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 disas-
sembly and reassembly procedures required for
component replacement.
Transmitters are precision instruments. Please carefully
and thoroughly read the following sections for informa-
tion 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 Se-
lection
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 specified accuracy.

8.3 Calibration

Use the procedure below to check instrument operation
and accuracy during periodic maintenance or trouble-
shooting.
1) Connect the instruments as shown in figure 8.1 and
warm up the instruments for at least five minutes.
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 figure.
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 confirm that the errors are within
the required accuracy.
8-1
8. MAINTENANCE
IM 01C25B01-01E