Danfoss W894A Manuel - Page 3

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DIMENSIONS

THEORY OF OPERATION

The amplifier section of the W894A supplies an excitation of

1.4 V-ac (440 Hz square wave) across Pins A and B of the

W894A's internal MS connector to the transducer. See the

Block Diagram. As the machine is tilted off the proper slope,

the rotor rotates with respect to the secondary coils. As the

rotor moves toward one secondary and away from the other,

the voltage induced in the coil toward the rotor is increased,

the opposite being true of the other secondary. At the full

10%-from-null slope (the rated maximum range), the voltage

across the secondary closer to the rotor is 5.3 V-ac, while the

other voltage is 4.2 V-ac.

ENVIRONMENTAL

OPERATING TEMPERATURE

-18° to 77° C (0° to 170° F)

STORAGE TEMPERATURE

-40° to 77° C (-40° to 170° F)

HUMIDITY

After being placed in a controlled atmosphere of 95%

humidity at 49° C (120° F) for 10 days, the W894A will

perform within specification limits.

RAIN

After being showered from all directions by a high

pressure hose down, the W894A will perform within

specification limits. This test fulfills NEMA 4 specifica-

tions.

Dimensions of the W894A in Millimeters (Inches).

The ac signals from the secondaries are applied to two

bridge rectifiers in the amplifier section, where each is

converted to dc. At null the voltages across both capacitors

are equal. When a change in secondary voltage is intro-

duced, the voltages across the capacitors are offset,

inducing a differential between the reference (which may be

a remote setpoint command) and the junction between the

capacitors. This differential serves as the positive or nega-

tive correction signal that is amplified and then supplied to

the servovalves to close the control loop. Control action

drives the machine to a position such that the sensor error

signal to the amplifier section is reduced to null.

VIBRATION

Withstands a vibration test designed for mobile equip-

ment consisting of two parts:

Cycling from 5 to 2000 Hz in each of the 3 axes.

Resonance dwell for one million cycles for each

resonance point in each of the 3 axes.

SHOCK

50 g's for 11 milliseconds. Three shocks in both direc-

tions of the 3 mutually perpendicular axes for a total of

18 shocks.

WEIGHT

3.4 Kg (7 pounds, 8 ounces)

DIMENSIONS

See the Dimension Drawing.

1182

BLN-95-8974-5