3.4 EMC
The G123-817 emits radiation well below the level called for in
its CE mark test. Therefore, no special precautions are required
for suppression of emissions. However, immunity from external
interfering radiation is dependent on careful wiring techniques.
The accepted method is to radially terminate the cable screens,
in an appropriate grounded cable gland, at the point of entry
into the industrial steel enclosure. If this is not possible, chassis
ground screw terminals are provided on the G123-817-006.
Exposed wires should be kept to a minimum length. Connect
the screens at both ends of the cable to chassis ground.
4 Power supply
24V DC nominal, 22 to 28V
60mA @ 24V, without an LVDT connected
160mA @ 22V, with 50mA oscillator load
If an unregulated supply is used, the bottom of the ripple
waveform is not to fall below 22V.
It is recommended that an M205, 250mA T (slow blow) fuse,
compliant with IEC 127-2 sheet 3, be placed in series with the
+24V input on terminal 1 to protect the electronic circuit.
5 Set-up adjustments
magnitude greater than the 300Hz electronic bandwidth pre-
set on the circuit card and enables the mechanical bandwidth
to match the electronic bandwidth. Initially, do not select any
phase adjustment. Connect a dual trace oscilloscope to front
panel test point
Vac
and circuit card
TP2
. Set an oscillator level
2
with the front panel
level
pot so that the signals are free of
noise and ripple, so a clear, easily read signal is displayed.
Ensure that the level is not so high as to distort the waveform.
Select other frequencies with the
frequency select
switches to
see if a minimum phase difference can be achieved. Select the
frequency that gives a minimum phase difference. Be aware
that there is an adjustment on the circuit card that reduces the
phase difference so it is not essential to achieve exactly zero
phase difference. Do not turn on all four switches together.
This is an invalid selection.
5.2 Excitation oscillator level
Set the LVDT manufacturer’s recommended excitation oscillator
level with the front panel
level
pot. The
Vac
test point gives
2
half of the actual level i.e.2.5V on the test point is equal to a
true 5.0V on the LVDT primary.
The excitation oscillator level is set by the front panel
osc.
(oscillator)
level
potentiometer. Note that the maximum
permissable primary voltage is 8.0V RMS.
Do not set the
oscillator level
greater than 8.0V RMS. The
maximum permissable LVDT full scale sensitivity is 0.9V/ V. Full
scale sensitivity is defined as the secondary voltage per volt of
primary voltage excitation, when the LVDT core is at full stroke.
With 8.0V RMS osc. voltage the secondary voltage input to the
G123-817-006 must not exceed 7.2V RMS, when the LVDT
core is at full stroke.
There are two limits on the maximum permissable secondary
voltage
• An absolute maximum of 8.0V RMS
• 0.9 times the osc. voltage.
When setting the
oscillator level
for the first time it is
advisable to observe the oscillator waveform on the
Vac
test
2
point, with an oscilloscope. For correct operation the waveform
should be a clean sinusoid. Maximum output current is 50mA
RMS. If the waveform is distorted, reduce the level until a clean
sinusoid is observed.
Slide S1 and S2 up to turn on.
Front panel potentiometers are 15 turns.
Bold
test refers to front panel controls.
Italic
test refers to circuit card controls.
Default shipping frequency is 3.1KHz.
Default shipping phase adjustment is zero.
5.1 Excitation frequency
Select the manufacturer’s recommended “zero phase”
excitation frequency with the internal
frequency select
switches. The circuit card will need to be withdrawn from
the case to do this. See paragraph six. If the recommended
frequency is not known, start off with 3.1KHz, the default
setting. This is a good starting point because it is an order of
S2 LEAD/LAG
S1 FREQUENCY
0V
TP2
DMOD
1
1
TP9
TP3
R6 PHASE ADJ.
SEC
S1-1
S1-2
S1-3
S1-4 f, kHz
✓
✓
✓
0.8
✓
✓
✓
1.7
✓
✓
2.5
✓
✓
✓
3.0
✓
✓
3.9
✓
✓
4.7
✓
✓
✓
5.1
✓
5.5
✓
✓
5.9
✓
✓
6.8
✓
7.6
✓
✓
8.1
✓
8.9
✓
9.7
10.5
Frequency selection,
✓
= switch on
Cable gland
100mm Loop
Cable
Enclosure
Cable
Wire soldered
to screen
Drain wire.
or
(Heat shrink to
cover the screen)
Alternative wiring
MOOG
Vac
zero
2
span
LVDT
LEDS
TEST POINTS
POT
POT
POT
output
Vs
level
osc.
TEST POINT
Page 2 of 4: C70880 Rev
E – 11.15
