EHH-AMP-702-J-20 by Vickers

The EHH-AMP-702-J-20 is an electronic amplifier module produced by Vickers and supplied within the Vickers Accessories series. It conditions low-level command signals and drives proportional solenoids in hydraulic control loops, allowing PLCs or analog controllers to regulate valve spool position with repeatable current output. By converting a ±10 V reference into a controlled current, the unit forms the link between motion logic and the electro-hydraulic actuator, making it a common accessory inside industrial automation manifolds and mobile machinery power packs.

This amplifier is intended for a nominal supply of 24 VDC, but it remains functional down to 20 VDC and must never be exposed to more than 40 VDC. Internal circuitry can draw up to 35 W while sourcing a peak coil current of 1.6 A, so the power source and thermal layout must accommodate that load. The command input is scaled for 10 VDC and presents a 10 k? impedance, minimizing loading on upstream analog cards. A 200 mV LED threshold provides quick visual confirmation that the reference loop is active. Current-sharing elements limit the typical output voltage drop to 1.5 V, so most of the bus voltage is available across the solenoid. A fixed dither frequency of 120 Hz reduces static friction in the valve, promoting smoother position control during small-signal operation.

For field installation, the housing is classified at IP67, sealing it against dust ingress and temporary water immersion. Pulse-width modulation of the coil is generated at 1200 Hz, giving fine current resolution while moving switching noise outside most hydraulic resonance bands. Reliable service is maintained from -20 °C to 70 °C, matching typical mobile and plant-floor temperature ranges. Cable glands accept jackets up to 10 mm in diameter, and the ISO 4400 (DIN 43650) mounting interface allows direct coupling to standard valve connectors without custom brackets.