AD598J 查看數據表（PDF） - Analog Devices

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AD598J

LVDT Signal Conditioner

Analog Devices 

AD598

1000

100

Figure 15. Gain and Phase Characteristics vs. Frequency

(0 kHz–10 kHz)

1000

100

10

10

10kHz , C SHUNT = 0nF

1

10kHz , C SHUNT = 1nF

10kHz , C SHUNT = 10nF

0.1

0.001

0.01

0.1

1

10

C2, C3, C4; C2 = C3 = C4 – µF

Figure 17. Output Voltage Ripple vs. Filter Capacitance

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,

VPRI (3 V rms for the E100). Set the core to midpoint where

VA = VB. Set the core displacement to its mechanical full-scale

position and measure secondary voltages VA and VB.

Sensitivity

= VA(at

Full

Scale ) – VB (at

VPRI × d

Full

Scale )

From Figure 18,

Sensitivity

=

1.71 – 0.99

3 × 100 mils

= 2.4 mV/V/mil

VSEC WHEN VPRI = 3V rms

VA

1.71V rms

1

0.1

0.01

2.5kHz, C SHUNT = 0nF

2.5kHz, C SHUNT = 1nF

2.5kHz, C SHUNT =10nF

0.1

1

10

C2, C3, C4; C2 = C3 = C4 – µF

Figure 16. Output Voltage Ripple vs. Filter Capacitance

0.99V rms

VB

d = –100 mils d = 0 d = +100 mils

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.

REV. A

–9–

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