9
In instances where corrosive and / or abrasive materials are be-
ing measured, the user must check the level of resistance of all
parts that are coming into contact with these materials. ABB
offers guidance in the selection of material but does not accept
liability in performing this service. The user must strictly observe
the applicable national regulations with regards to installing,
functional testing, repairing and maintaining electrical devices.
4.6 Suggested Proof Test
The suggested proof test consists of minimum and maximum
current capability test followed by a two-point calibration of the
transmitter, see the suggested proof test Table. This test will
detect > 99% of possible DU failures in the device.
4.7 Safety Inspection & Test
An MT5000 transmitter can be divided into three major compo-
nents, the sensor, the transmitter, and the output. All of these
components and their subcomponents should be evaluated dur-
ing each periodic inspection. This inspection (and possible re-
pair) should take less than 4 hours if the proper tools are made
available. Prior to inspection, the transmitter should be removed
from service following end user specified procedures regarding
lockout, tag out, wiring and cleaning. Once removed from ser-
vice, the MT5000 transmitter should be laid on a flat even sur-
face.
4.7.1 Sensor Inspection
The rod or cable assembly should not be damaged or corroded in any
way. Additionally, it should not be touching any of the surrounding
tank or chamber surfaces in the measurement range.
4.7.2 Transmitter Testing
The transmitter of the MT5000 is designed to return a level indica-
tion and an output based on a dielectric constant change between
the upper fluid or vapor and the lower fluid. If the transmitter is
equipped with an LCD the level and output will be displayed on the
front of the electronics module.
1) Apply power to the transmitter using the typical power setup for
the particular option.
2) Move a high dielectric object such as a metal target plate up and
down the sensor.
3) Monitor the indication of the level on the LCD to make sure the
indication corresponds to the target position.
4) Make sure the transmitter responds with an Alarm Indication
(based on the jumper position) and a corresponding level indication
based on your setup (HIGH = 21.00 mA, LOW = 3.61 mA)
Note: It is possible for the MT5000 to continue providing a 4-20mA
output if the LCD display is not functioning properly. If the LCD indi-
cator on an electronics module fails to operate, it is recommended
that the electronics module be replaced at the earliest convenience. It
will not be necessary however to shut down a transmitter or remove
it from service based on an LCD failure.
4.7.3 Output Checkout
The MT5000 can be equipped to provide level indication through the
4-20mA output, HART communications and Foundation Fieldbus.
Only transmitters that are specified to output 4-20mA may be used
in a Safety Implemented System. The HART communication capabil-
ity of the 4-20mA transmitter will only be used for configuration and
proof testing.
4.7.3.1 Analog 4-20mA Output
The current output of the MT5000 transmitter update at least every
110 milliseconds and be filtered through the user adjusted Damping.
The maximum response time to a process change will be less than
110 milliseconds or the value of the Damping, whichever is greater.
1. Apply power to the transmitter using the typical loop wiring diagram.
2. Connect a multi-meter (set to read milliamps) to the transmitter
using the Meter connections on the terminal strip.
3. Move a high dielectric object such as a target plate along the
length of the probe and monitor the milliamp output on multi-meter .
4. The output should indicate the target position based on the cali-
bration range of the transmitter.
4.7.3.2 HART Output
1. Apply power to the transmitter using the typical loop wiring diagram.
2. Connect a HART handheld device across a 250 ohm resistor in se-
ries with the loop.
3. Move the target along the length of the probe and monitor the PV
indication on the handheld device.
4. The output should indicate the target position based on the cali-
bration range of the transmitter.
Note: A HART handheld device will communicate with the MT trans-
mitter. The Device Descriptors are available on the ABB website. If
the output of the transmitter becomes latched, the HART handheld
will respond with a warning that the Process Variable is out of range.
To overcome the error, press OK when prompted to ignore the next
50 occurrences.
MT5000 Suggested Proof Test Table
1.
Bypass the safety function in the control system and take
appropriate action to avoid a false trip.
2.
Use HART communications to retrieve any diagnostics and
take appropriate action.
3.
Send a HART command to the transmitter to go to the high
alarm current output and verify that the analog current
reaches that value.*
4.
Send a HART command to the transmitter to go to the low
alarm current output and verify that the analog current
reaches that value. **
5.
Perform a two-point calibration*** of the transmitter over
the full working range.
6.
Remove the bypass and otherwise restore normal opera-
tion.
Notes:
This tests for compliance voltage problems such as a low
loop power supply voltage or increased wiring resistance.
This also tests for other possible features.
** This tests for possible low current related failures.
*** If the two-point calibration is performed with electrical
instrumentation, this proof test will not detect any failures
of the sensor.
Summary of Contents for MT series
Page 12: ...12 7 Typical Wiring Drawing ...
