IM-P192-02
MI Issue 2
47
5. Maintenance
The TVA flowmeter should be zeroed using the zero meter sub-menu at least once a year.
This will remove any electronic long term drift that may occur. Frequency of re-calibration
depends upon the service conditions experienced by the meter and the application.
Re-calibration frequency can be typically between 2 and 5 years.
5.1 Replacement of the TVA flowmeter display electronics
To replace the electronics:
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Disconnect the power supply.
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Remove the front housing.
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Remove the mounting screws on the display unit and carefully remove the electronics.
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Carefully unplug the ribbon cable.
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Reconnect the ribbon cable to the new electronics and carefully replace.
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Replace the mounting screws and reconnect the power supply.
Note:
Electrostatic discharge (ESD) procedures should be followed while installing the new
electronics.
Do not force the electronics/display unit into position.
Important note:
The TVA is a loop powered device. It requires the CTS and DTR terminals
to be wired and enabled to power the communications interface. Failure to do so will prevent
the communications working.
4.14.3 Response time:
The TVA will start responding within 500 msec. The actual time to fully receive a response
from the TVA is baud rate dependent, for example a Modbus poll of 12 registers @1200 baud
rate could take ((5 + 24) bytes x ~10 ms / byte) + 500 ms ≈
800 ms
to complete.
The polling frequency can be faster if the polling algorithm is set to poll immediately after
receiving a valid response to a poll.
