Automating hydraulic control valve test sequences — ramp signals, data acquisition, and performance metric calculation — here's how the process works.
Test Signal Generation
Valve performance testing starts with generating a controlled command signal that ramps smoothly between two command percentages over a set duration, sampled at a fixed rate (typically 10 Hz). This produces a clean, repeatable command profile and a matching timestamp series, which together drive the valve controller through a known motion sequence.
For SAE J1271 compliance testing, the full sequence runs through several stages: a warm-up period holding the valve at 50% command for five minutes to stabilize fluid temperature and viscosity, a forward ramp from 0% to 100% command over 60 seconds, a reverse ramp back down, and small-signal steps near the null position to characterize deadband and hysteresis. Command signal, measured flow, and pressure are logged with timestamps at every stage for later analysis.
Performance Metric Calculation
Once the raw command and response data is captured, the test rig software calculates the performance metrics that determine whether a valve passes or fails specification.
Hysteresis is measured as the maximum difference in output flow between the forward ramp and reverse ramp at the same command value, expressed as a percentage of full-scale flow. Deadband is the command range near the null position where no measurable flow output occurs. Flow gain and linearity come from comparing the actual flow curve against the ideal linear response across the full command range.
These metrics feed directly into an automated test report, so every valve that ships carries objective, repeatable evidence that it meets its hysteresis, deadband, and flow curve specifications — without relying on manual stopwatch-and-gauge testing.
Read more about the Control Valve Test Rig.
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