ECS Test Bench DAQ Architecture: Multi-Parameter Environmental System Testing

#engineering #testing #aerospace #sensors

An ECS test bench has more simultaneous measurement channels than most industrial test systems — temperature at 6–10 locations, pressure at 4–6 points, mass flow, humidity, and sometimes shaft speed. Here's how to structure the DAQ.

Sensor Map

ECS Inlet ──► [T1: Bleed air temp] [P1: Bleed air pressure]
    │
    ▼
Air Cycle Machine
    │
    ├── [N1: ACM shaft speed (RPM)]
    │
    ▼
Primary Heat Exchanger
    │
    ▼
Water Separator ──► [RH1: Humidity at separator outlet]
    │
    ▼
Mix Valve ──► [T2: Cold air temp] [T3: Hot bypass temp]
    │
    ▼
ECS Outlet ──► [T4: Delivery air temp] [P2: Delivery pressure]
              [Q1: Mass flow (kg/min)] [RH2: Humidity at outlet]

DAQ Configuration

Ten channels cover the full thermodynamic path: four PT100 RTDs for temperature, three strain-gauge pressure transducers, a Coriolis mass flow meter, a capacitive humidity sensor, and a magnetic pickup for ACM shaft speed. Every channel is sampled at 10 Hz and logged to file once per second, with each channel's measurement range matched to its physical location in the system — from the 0–700°C bleed inlet down to the −20 to 60°C delivery air.

Steady-State Detection (Critical for ECS Testing)

ECS thermal equilibrium takes 5–15 minutes. Never record performance data during transients: the bench collects a rolling 120-second window of temperature history on each critical channel, and only declares steady state once the spread across that window falls within ±0.5°C. If any of the three critical channels — delivery air, ACM outlet, or heat exchanger outlet — is still settling, the system keeps waiting rather than logging a transient reading as performance data.

Performance Calculation

Once steady state is confirmed, the bench reduces the buffered data into the parameters that actually matter for an ECS report: cooling effectiveness (how much of the available temperature drop down to ram air conditions was actually achieved), pressure recovery across the system, delivered mass flow, and outlet humidity. These are computed from mean values across the steady-state window, not single-point readings, so the reported numbers reflect settled system performance rather than instrumentation noise.

The Neometrix ECS Test Bench Model A0624 implements this DAQ architecture with automated steady-state detection and performance report generation.
→ https://neometrixgroup.com/products/ECS-test-bench