KROHNE ALTOSONIC V12 EN - Manual (Page 85)

SERVICE
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85
ALTOSONIC V12
www.krohne.com 04/2013 - 4002643502 - MA ALTOSONIC V12 R02 en
Step 3: Test the suspected transducer
The electronic measuring instrument is not supplied as part of the kit. It can be any instrument
suitable to measure a capacitance in the range of 0.1 ...1.0 nF and an electric resistance in the
range of 1 MΩ ... 20GΩ. This is a fairly common device and supposed to be available.
• Position the connector of the coax adapter cable in the connector in the transducer.
• Measure the electrical capacitance of the transducer. The value must be 0.32...0.34 nF.
• Measure the electrical resistance of the transducer. The value must be > 10 MΩ (typical value
= 1 GΩ).
• Release the adapter cable.
Step 4: Put the transducer adapter in position
• Position the transducer adapter in such a way that it will (partly) engage with the transducer
fastening nut.
• Turn the transducer adapter - together with the transducer fastening nut - counter clockwise
(not more than one turn) to allow the pin inside the transducer adapter to slide into the slot in
the extension with M10 screw thread on top of the transducer.
INFORMATION!
Before starting the operation to replace a transducer care must be taken to make sure which
transducer is suspect to be failing. As a start the diagnostic tool to check the performance of the
ultrasonic gas flowmeter shall be used for this purpose. In case of doubt consult the local
support organisation of the manufacturer. Be aware transducers always operate as pairs
(belonging to the same acoustic path). Therefore, using this diagnostic tool it may not be certain
which one of a pair needs to be replaced.
Secondly the electrical capacitance and resistance of the suspect transducer can be measured
to identify which transducer of an acoustic path is suspect. An observation of a low resistance
value or a capacitance value deviating from specification can be a helpful confirmation for
identifying a transducer that may be failing.
Figure 8-20: Mount transducer adapter
1 Transducer and fastening nut inside the flowmeter.
2 Transducer adapter.
3 Wrench