A compressor test rig generates continuous multi-channel data — pressure at 5+ locations, temperature at 4+ locations, flow, speed, and power — across tests running hours to days. Here's the data architecture.
Sensor Channel Configuration
The rig instruments ten channels across the oil and air circuits. Pressure is monitored at the compressor suction (0–2 bar), discharge (0–16 bar), oil cooler inlet (0–16 bar), and reservoir (0–16 bar) using 4–20mA pressure transmitters. Temperature is tracked at the oil cooler inlet and outlet (0–150°C and 0–130°C) and at the compressor discharge (0–150°C) using PT100 RTDs or type-K thermocouples. Oil flow through the circuit is measured with a turbine flowmeter rated 0–150 lpm. Motor speed (0–3000 rpm) comes from VFD feedback, and motor power (0–20 kW) comes from an energy meter.
Steady-state channels are logged at 1 Hz, while alarm channels sample at 10 Hz during transients and startup to catch fast-moving events.
Steady-State Detection and Test Phase Management
Compressor oil tests require thermal steady state before any data point is considered valid — typically 20–30 minutes at each operating point. The detection logic checks a rolling window (commonly 10 minutes) of the oil cooler outlet temperature, compressor discharge temperature, and discharge pressure. If the spread between the highest and lowest reading in that window stays within tolerance — 2°C for temperature channels and 0.2 bar for pressure — the system flags steady state as confirmed. If any channel is still drifting beyond tolerance, the test phase remains in "warmup" and logging continues until the readings settle.
Oil Condition Trending
Periodic oil samples sent to the lab return viscosity and acid number readings that get tracked against test hours. A linear trend is fitted to both viscosity and acid number over time, giving a rate of change per hour for each. Using the acid number trend and a typical change-out threshold — an increase of 1.5 mgKOH/g above the new-oil baseline — the system projects how many operating hours remain before the oil should be changed. If the acid number isn't rising, the oil is flagged for continued monitoring rather than replacement.
The Neometrix Compressor Test Rig implements this DAQ architecture with PLC-based continuous logging and automatic alarm management.
→ https://neometrixgroup.com/products/compressor-test-rig
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