Metek RCT 10 series, Installation And Operating Instruction

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Troubleshooting
59
Problem/Symptom Tests in order of probability Reference Section(s) Comments
Rosemount 268 or 275
Calibrator gives error
message that no device was
found
Check calibrator connections
Check for 250
Ω
resistance (min.)
Check voltage at transmitter
Check transmitter
6.2 and 6.3
6.6
Often a result of loop
connection problems
Rosemount 275 Calibrator
gives error message
that device could not be
identified
Check calibrator connections
Check for 250
Ω
resistance (min.)
Check voltage at transmitter
Check transmitter
6.2 and 6.3
6.6
Often a result of loop
connection problems
Can’t communicate
with transmitter using
Drexelbrook PC Software
Check calibrator connections
Check for 250
Ω
resistance (min.)
Check voltage at transmitter
Check transmitter
Try another modem
6.2 and 6.5
6.6
Often a result of loop
connection problems
0 mA output all the time
(no measurable output
current at any time)
Check voltage at transmitter
Check polarity of loop
Test Transmitter
6.2 (6.3, 6.4, or 6.5)
6.6
Probable loop
problem
Faulty connection in
loop
More than 20 mA output
all the time (output current
always exceeds 20 mA)
Check for moisture in head of sensor
Test Sensing Element
Test Transmitter
Check Calibration
6.7
6.6
Section(s) 3, 4, and 5
Output drifts (output
accuracy varies slowly over
time…e.g. hours or days)
Test transmitter without sensing element
(drift test)
Verify proper sensing element ground
reference
6.6
Fig. 2-6
Output erratic - (output
jumps around noticeably
in terms of seconds or
minutes)
Test Transmitter
Check process level
Check for Static Discharge
Check for radio interference
6.6
6.9
6.10
Erratic readings
often show actual
process conditions.
Look for bubbles or
stratification, etc.
Output intermittent (output
jumps quickly usually
between >0mA and some
"on scale" value
Check Signal Loop Connections 6.7
6.8
Intermittent Loop
Connection
Inaccurate readings (Level
readings are incorrect
compared to actual known
level)
Check calibration
Test transmitter
Check method of comparison
Section(s) 3, 4, and 5
6.6
Have you verified
actual level? (At
times even sight
gauges can be
misleading.)
Reading does not change
with level
Check cables
Check sensing element
Test Transmitter
6.8
6.7
6.6
Be sure that level
is really changing.
Possible plugged or
unvented stilling well.
Output goes in opposite
direction from level change
Check calibration Section(s) 3, 4, and 5 Probable high point
cal/low point cal
reversal or inverted
interface application.
Application-related
Problems
Comments
Product Bridging When process material fills what was originally airspace between the sensor and a nozzle
or the vessel, it no longer behaves like a coating. It measures like actual level. Contact
Drexelbrook.
Corrosion of metal parts TFE and stainless steel in the sensor's pressure seal have widely different coefficients
of expansion that sometimes permit pressure leaks to occur. Re-torqueing the packing
assembly can usually fix the problem. Contact the Service department for the proper
torque values and procedure.
SECTION 6: TROUBLESHOOTING
Table 6-1
Problem / Symptom Chart