AD598 Analog Devices, AD598 Datasheet - Page 9

• Manufacturer Part Number: AD598
• Description: LVDT Signal Conditioner
• Manufacturer: Analog Devices

REV. A
Figure 15. Gain and Phase Characteristics vs. Frequency
(0 kHz–10 kHz)
Figure 16. Output Voltage Ripple vs. Filter Capacitance
1000
100
0.1
10
1
0.01
C2, C3, C4; C2 = C3 = C4 – F
0.1
1
2.5kHz, C
2.5kHz, C
2.5kHz, C
SHUNT
SHUNT
SHUNT
=10nF
= 0nF
= 1nF
10
–9–
Determining LVDT Sensitivity
LVDT sensitivity can be determined by measuring the LVDT
secondary voltages as a function of primary drive and core posi-
tion, and performing a simple computation.
Energize the LVDT at its recommended primary drive level,
V
V
position and measure secondary voltages V
From Figure 18,
Figure 18. LVDT Secondary Voltage vs. Core Displacement
Thermal Shutdown and Loading Considerations
The AD598 is protected by a thermal overload circuit. If the die
temperature reaches 165 C, the sine wave excitation amplitude
gradually reduces, thereby lowering the internal power dissipa-
tion and temperature.
Due to the ratiometric operation of the decoder circuit, only
small errors result from the reduction of the excitation ampli-
tude. Under these conditions the signal-processing section of
the AD598 continues to meet its output specifications.
The thermal load depends upon the voltage and current deliv-
ered to the load as well as the power supply potentials. An
LVDT Primary will present an inductive load to the sine wave
excitation. The phase angle between the excitation voltage and
current must also be considered, further complicating thermal
calculations.
PRI
A
Figure 17. Output Voltage Ripple vs. Filter Capacitance
= V
(3 V rms for the E100). Set the core to midpoint where
Sensitivity
B
1000
. Set the core displacement to its mechanical full-scale
100
0.1
10
1
0.001
Sensitivity
d = –100 mils
V
V
SEC
A
0.01
(at Full Scale ) – V
C2, C3, C4; C2 = C3 = C4 – F
WHEN V
3 100 mils
1.71 – 0.99
d = 0
PRI
= 3V rms
0.1
V
d =
PRI
10kHz , C
+
10kHz , C
10kHz , C
100 mils
2.4 mV/V/mil
B
d
V
A
1.71V rms
(at Full Scale )
0.99V rms
A
V
B
and V
1
SHUNT
SHUNT
SHUNT
AD598
= 10nF
B
= 0nF
= 1nF
.
10