Nordson 3100V Series Customer Product Manual page 259

B
2-26
Control
Checking an RTD or RTD
Circuit
(contd.)
Table B
2-6 Measuring RTD Resistance
Quick Methods ln-Depth Methods
Using a
surface-temperature sensing device, such as a
thermocouple, measure the temperature of the
RTD
at
or near the end
of
the RTD that
is
accessible. Then
use
an ohmmeter
to measure its resistance (See Note A).
See Figure
B
2-6 and compare the resistance reading to
the RTD's normal resistance at the known temperature.
Let the system
cool down to
room
temperature. When
the
RTD has had time to reach room temperature, use
an ohmmeter to measure its resistance (See Note A).
See Figure B
2-6 and compare the resistance reading
to
the
RTD's
normal resistance at room temperature.
Roughly estimate the temperature
of
the
RTD to the
nearest 50 'C
(100
'F).
Use an ohmmeter to measure
its resistance
(See Note
A).
See Figure
B
2-6 and
compare the resistance reading to the RTD's normal re-
sistance
at
the estimated
temperature. Because
RTDs
usually fail
open or closed, any resistance reading from
approximately 100-400 ohms strongly indicates'that the
RTD is good.
Remove
the RTD and heat
it
to a known temperature
by using
an oven or by placing it in boiling water (pro-
tect the wires and hold them above the
water). Then
use an ohmmeter to measure its resistance
(See Note
A).
See Figure
B
2-6 and compare the re-
sistance reading to
the
RTD's
normal resistance at the
known temperature.
NOTE
A:
lf the
faulted zone is a hose or gun, measure the
RTD resistance at
the hose or gun electrical plug.
Refer
to your hose or gun manual for a diagram
of
the electrical plug and for procedures for checking
RTD
resistance.
Because
the core elements of a hose are not accessible, you cannot use some of the
methods described
in
this table to measure the temperature of a hose
RTD.
lf the faulted zone is a
tank, meadure the resistance at pins 33 and 34
of
the harness attached to connector XP2 on the control
board.
41
-3000v
lssued
5/00
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