YOKOGAWA vigilantplant DM8, User Manual

Page: 56 / 63

<5. MAINTENANCE>
5-3
IM 12T03A01-02E
5.2.3 Checking the Oscillation Amplifier
First, visually inspect the capacitance pickup electrode. This electrode should be installed 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.
F0502.ai
Check point
1
2
3
4
5
6
7
8
9
Measuring instrument Measuring conditions Normal value
12 V±10 %
200 V±10 %
5.8 to 6.4 V
∞ (X 10 kΩ Range)
6 to 8 V p-p
150 to 200 V p-p
200 mV p-p
4 to 6 V p-p
-3 to 0 V
A5 – B5
A6 – B5
B – B5
IN –
B4 – B5
R – B5
A – B5
C – B5
D – B5
DC voltmeter
For measurement of 2 ,
the meter input impedance
should be at least 10 MΩ
Multimeter
Oscilloscope
DC voltmeter
Disconnect leadwires from terminals
IN, R, and B, on PCB, connect an
oscillator (0 to 2000 Hz, output 5 V),
and apply an input of 100 mV rms.
Lower 100 mV rms input
Remedial measure
for abnormal value
Check converter INPUT
assembly.
Replace D8.
Check pickup electrode.
Check for defective circuit
components and replace
them.
Terminal
Box
Black
White
Blue
Yellow
Green
Brown
Green
Pt1000
White
A5
A6
IN
B5
A2
A3
A4
Y1
Y2
Y3
Red
B4
B
R
Black
Red
Piezoelectric
element
Case ground
C
D
B
D8
1mS
6V
A
Vibrator output
wavefarm between
B4 and B5 when
density detector is
operating normally.
(Note): Regarding to repair parts, consults with service personnel.
Figure 5.3 Oscillation Amplifier Check Points
5th Edition : Dec. 11, 2015-00