Model Definition

D661 = Series (integrated electronics, 24 VDC, NG10)

4651 = Spool/sleeve assembly; rated flow 30 L/min @ ΔP=35 bar

G35HOC = Configuration code breakdown:

G = ServoJet® pilot stage, standard spool

35 = Frequency response class (≥120 Hz bandwidth)

H = High‑response version, enhanced dynamics

O = Null position: centered (fail‑safe, power‑off centering)

C = Analog command: ±10 V / ±10 mA, industrial connector

Technical Specifications

Hydraulic Parameters

Rated flow: 30 L/min (ΔP=35 bar)

Max working pressure: 350 bar (P/A/B); 210 bar (internal drain T) / 350 bar (external drain T)

Step response: 6.5–10 ms (0→100%, 210 bar, high‑response tuning)

Hysteresis: <0.2%

Resolution: <0.1%

Null drift: <1.2% (ΔT=55 K, improved for high‑response)

Null leakage: <8 mL/min

Fluid cleanliness: NAS 1638 Class 6 / ISO 4406 18/15

Electrical Parameters

Power supply: 24 VDC (18–32 VDC)

Control signal: ±10 V (differential) or ±10 mA

Feedback signal: 4–20 mA (LVDT spool position, standard)

Connector: 6+PE, IP65

Current draw: ≤300 mA

Physical & Environmental

Operating temperature: −40 ℃ to +85 ℃

Weight: approx. 5.1 kg

Interface & Communication Configuration

Hydraulic interface: P/A/B/T, ISO 4401‑05 (NG10)

Electrical interface:

Power: 24 VDC, GND, PE

Command: ±10 V / ±10 mA

Feedback: 4–20 mA (spool position)

Status: Fault alarm output

Core Functions

ServoJet® pilot stage: Excellent contamination resistance, low null drift, long service life

Integrated high‑response amplifier: Built‑in PID, dead‑zone compensation, overload protection

LVDT closed‑loop feedback: High linearity and precision across full stroke

Fail‑Safe centering: Spool returns to neutral on power loss

G35 high bandwidth: ≥120 Hz for fast dynamic applications

Application Scenarios

Metallurgy: High‑speed AGC roll gap control, tension control

Test equipment: Dynamic material testers, fatigue test benches, high‑frequency vibration tables

Industrial automation: Precision CNC machine tools, high‑speed injection molding machines

Energy & heavy industry: Wind turbine pitch control, shield machine auxiliary control

Usage & Maintenance

Installation: Horizontal/vertical mounting; avoid severe vibration

Fluid: ISO VG46 mineral oil; maintain cleanliness per NAS 1638 Class 6

Commissioning: Apply 24 VDC power; connect ±10 V/±10 mA command; calibrate zero and gain via 4–20 mA feedback

Maintenance: Inspect fluid contamination regularly; calibrate zero/gain every 6 months; avoid long idle periods at high pressure