Optical spectrometer CAPS-DPOL

for research and developmentfor environmental analysisreal-time

Overview
The CAPS-DPOL is a research-grade, multipurpose cloud spectrometer integrating three droplet probes (Cloud Imaging Probe — CIP, Cloud and Aerosol Spectrometer with Depolarization — CAS‑DPOL, and Hotwire Liquid Water Content sensor — LWC), plus ambient temperature and relative humidity sensors and polarization measurement for water/ice discrimination.

Features and benefits

• Comprehensive data — Combined probes cover particle sizing from submicron aerosols to large precipitation (approximately 0.51 µm to 1.55 mm across probes).
• Versatile measurements — CAS‑DPOL: 0.51–50 µm; CIP: 12.5 µm–1.55 mm (standard); LWC: ~0.01–3 g/m3 (sensor-dependent).
• Polarization-enabled discrimination — CAS‑DPOL provides depolarization/backscatter channels to differentiate spherical (liquid) and aspherical (ice) particles.
• System integration — Includes ambient T/RH sensors, aircraft velocity and pressure inputs; optional Lifecycle Care Program and accessory modules.

Technology

• Particle imaging using a 64-element linear photodetector array (CIP) producing shadow images reconstructed from sequential slices.
• Light-scattering detection with forward- and back-scatter polarized channels (CAS‑DPOL).
• Hotwire LWC sensing using a temperature-controlled coiled wire in a Wheatstone bridge to derive liquid water content from evaporative power.

CAS-DPOL
Collects forward-scattered light for size determination and polarized back-scatter to assess particle shape and enable water/ice discrimination.

LWC (Hotwire)

• Coiled sensing wire maintained at ~150 °C acting as temperature-dependent resistance.
• Power required to maintain coil temperature is used to calculate vaporization and derive LWC.

Main applications

• Cloud physics and microphysics research
• Climate model input and radiative forcing studies
• Weather modification and precipitation research
• Pollution and aerosol characterization

PADS – Particle Analysis and Display System (optional)

• Start/stop data recording and sampling control.
• Real-time CIP particle image display and playback.
• Display particle volume/number concentrations, Median Volume Diameter (MVD) and Effective Diameter (ED).
• View and compare LWC from hotwire, CIP and CAS; monitor instrument status and telemetry.

Accessories

• PADS software and laptop (optional)
• Data Acquisition System (optional)

Technical comparison
Parameter — CIP Specification — CAS Specification — LWC Specification
Technique — Optical array probe, 64-element linear detector (62 sizing elements) — Forward- and back-scatter light sensors with depolarization — Temperature-controlled hotwire sensor
Measured size range — 12.5 µm – 1.55 mm (CIP) — 0.51 µm – 50 µm (CAS‑DPOL) — N/A; LWC 0–3 g/m3
Sample area — 10 cm × 1.55 mm — 11.1 mm × 120 µm — N/A
Upper concentration range — Up to ~500 particles/cm3 (CIP, depends on tip) — >1,000 particles/cm3 after coincidence corrections — 3 g/m3
Air speed range — 10–300 m/s (CIP) — 10–200 m/s (CAS, LWC) — 10–200 m/s
Size bins — 62 (CIP) — Selectable 10/20/30/40 (CAS) — N/A
Sampling frequency — 1D: 0.05–40 Hz; 2D: variable — Selectable 0.05–40 Hz — N/A
Laser — 658 nm (~30 mW CIP; ~50 mW CAS) — —
Data interface — RS-422 for 2D CIP (high speed) and system telemetry — —
Weight — Example probe system ~20.4 kg (45 lb)
Power — 28 VDC supply; typical 10 A for probe electronics; anti-ice heaters up to 45 A (optional)
Environment — Operating 0–40 °C; RH 0–100% non-condensing

Technical specifications

• Model: CAPS-DPOL
• Brand: ENVEA
• Included probes: CIP, CAS‑DPOL, Hotwire LWC
• CAS measured range: ~0.51–50 µm
• CIP measured range: ~12.5 µm–1.55 mm (standard)
• LWC range: ~0.01–3 g/m3 (sensor-dependent)
• Imaging detector: 64-element linear photodetector array (CIP)
• Lasers: 658 nm (power varies by probe)
• Data interfaces: RS-422 for 2D CIP and system telemetry
• Weight (probe system example): ~20.4 kg (45 lb)
• Power: 28 VDC supply; anti-ice heaters optional
• Operating conditions: 0–40 °C; RH 0–100% non-condensing