EM-D-30 by Vickers

The EM-D-30 is an amplifier board produced by Vickers and supplied in the Vickers Amplifier Boards series. In hydraulic and electro-hydraulic control loops, the board conditions command and feedback signals and then drives a proportional valve solenoid stage, providing a compact interface between low-level electronics and power-actuated flow control elements. Its opto-coupled alarm output keeps fault isolation separate from process grounds, and the board format allows direct installation in standard card cages used in industrial automation racks. Because signal conditioning and solenoid drive are handled on one card, the control rack can keep low-level command processing separate from valve power output. This layout suits proportional valve systems that require electrical isolation and consistent analog response.

The signal path supports dynamic operation, with bandwidth extending to 6 kHz at -3 dB and maximum gain, allowing the card to reproduce fast valve position changes without significant attenuation. At the input, the circuit tolerates an absolute maximum of 10 V DC, which helps protect the preamplifier against field wiring transients. The power stage can deliver 600 mA into a 20 ? solenoid, and its supply drift is limited to ±0.001 mA/V, so load current remains stable as cabinet voltage changes. The board is 127.0 mm long and includes temperature compensation, keeping the power stage current shift low even when ambient temperature changes. The preamplifier produces 2 mA at 10 V DC, giving the voltage amplifier a predictable drive point.

Long-term accuracy is supported by a voltage amplifier whose 24-hour output change is held to ±0.005 V DC. Under steady conditions, it sources 5 mA at a nominal 6 V DC, while supply drift remains at ±0.0001 V/V and temperature drift remains at ±0.0002 V/V. Warm-up behavior is also controlled, as the amplifier settles from a cold start with only ±0.004 V drift and the null current moves by no more than ±0.1 mA. Stable output helps limit valve spool drift during extended operation in pressure, speed, and directional control circuits. That behavior supports repeatable metering in circuits where small current changes can alter flow or pressure.