Product Description:

The VT-SR7-1X/0/A4VS.125HS is a plug-in servo amplifier card produced by Bosch Rexroth Indramat within the VT-SWMA Modules series. It conditions analog command inputs and generates a controlled dithered output current that drives proportional pilot valves used in hydraulic cylinders and pump controllers. By bridging low-power control electronics and high-power hydraulics, the card provides stable valve positioning, faster null breakout, and minimized hysteresis in industrial automation systems such as presses, injection machines, and test rigs.

Stable power is supplied to the internal op-amps through an auxiliary rail of ±15 VDC, and the module expects the command potentiometer on channel one to present a resistance of 50 kΩ. To improve spool responsiveness, the board injects a dither signal fixed at 340 Hz, which helps prevent static friction in the valve. The output stage can source or sink up to ±60 mA, enabling direct connection to proportional solenoids without external boosters. All functions are referenced to a system bus that must provide an operating voltage of ±24 VDC, and the integrated relay becomes active when a control line reaches +24 V, allowing remote enable from a safety circuit.

In quiescent mode, the amplifier draws only <150 mA, which helps limit cabinet heat rise while the channel is disabled. The relay coil itself has a resistance of 700 Ω, which allows the energizing current to be calculated within the permissible supply span. For the ±15 V rail, the allowable window extends from ±14.8 V to ±15.2 V, and the ±24 V rail may vary between ±22 V and the upper ceiling of ±28 VDC without loss of regulation. Because the card does not include an internal ±15 V voltage regulator, those margins must be met by the external power supply to maintain linear amplification across temperature and load changes.