2 troubleshooting, 1 checking the vibrators, 2 checking the rtd – Yokogawa DM8C/VD6 Liquid Density Analyzer User Manual
Page 56: 3 checking the oscillation amplifier, Checking the vibrators -2, Checking the rtd -2, Checking the oscillation amplifi er -2, Caution
< 5. MAINTENANCE >
5-2
IM 12T03A01-02E
5.2 Troubleshooting
Experiences are required for repair of the vibration type density meter; after parts are replaced,
adjustment may be necessary. If trouble occurs, as a rule, repair should be made by Yokogawa. In this
case, detailed information on abnormal phenomena will be effective for speedy recovery.
Searching method for abnormality is explained below. For the explosionproof detector, confi rm that
there are no explosive gases using a gas detector before removing the terminal box cover.
5.2.1 Checking the Vibrators
Remove the cover of the detector, so that the vibrator can be visually inspected.
Carefully check the entire surface of the two tubular vibrators. If they have dents, scratches, holes or
show signs of the sample liquid leakage, the vibrator assembly should be exchanged. (CAUTION)
Make sure that the lock-screw is not in contact with the vibrator assembly.
CAUTION
The vibrator tube has extremely thin wall, hence must be carefully handled.
Since assembling the vibrator tube requires special skill, the exchange of the vibrator should be made
by Yokogawa.
5.2.2 Checking the RTD
Measure electrical resistance between the terminal A2 and A3. When the RTD is normal, the
resistance shows the value indicated in the following table.
Table 5.1
Resistance at each temperature of RTD (Pt 1000Ω)
Temperature (°C)
10
15
20
25
30
35
40
45
50
Resistance (Ω)
1039.0 1058.5 1077.9 1097.3
1116.7
1136.1
1155.4
1174.7
1194.0
5.2.3 Checking the Oscillation Amplifi er
First, visually inspect the capacitance pickup electrode. This electrode should be unstalled near the
vibrator with a small gap between them. Without this gap, the electrode will not function properly. If
there is moisture or dirt between the electrode and vibrator, clean the gap with a cloth. Take care not to
damage the vibrator.
Then, check the electrical circuitry using a DC voltmeter and other appropriate measuring instruments.
For the types of instruments and the checkpoints, see Figure 5.3.