Modular Data Acquisition Platform
AccQ Series
Environmental Monitor
High-precision telemetry for chiller-plant efficiency & airside metrics
The AccQ Environmental Monitor is a flexible, modular data-acquisition platform engineered to
extract the precise telemetry required to control, monitor, and optimize HVAC operations.
Interfacing seamlessly with multiple sensor types, it delivers critical operational parameters —
including high-accuracy heat-flow and heat-balance calculations — purpose-built to meet the
stringent measurement and reporting standards mandated by the Singapore Government for chiller-plant
efficiency characterization and Green Mark compliance.
±0.0022°C
Temp uncertainty @ 10°C
24
Thermistor inputs (max)
32
dI²C environmental sensors
kW / RT
On-edge efficiency output
1 System Architecture & Modules
The AccQ hardware features a scalable chassis design available in multiple widths, accommodating a
core power/control layer and up to four interchangeable precision sensor modules.
Power Module
Supplies all internal digital and analog voltages from a universal 110–240 V, 50/60 Hz
supply input.
Controller Module
High-performance 32-bit MCU with Wi-Fi and Ethernet, 2× RS485 Modbus-RTU ports, and
4× differential-I²C (dI²C) ports.
PTT Modules (×1–4)
Precision Thermistor Thermometer modules, 6 high-precision channels each — a maximum system
capacity of 24 thermistor inputs.
Physical Dimensions
- Height: 185 mm
- Depth: 100 mm
- Width: 150 mm (3-slot chassis) or 300 mm (6-slot chassis)
2 Advanced Sensor Interfacing
Precision Temperature & Delta-T Measurement
The PTT module achieves an exceptional resistance-measurement accuracy of ±0.01% ±0.25 Ω,
corresponding to a temperature uncertainty of ±0.0022°C @ 10°C (using Amphenol Type F
material) — critical for verifying complex chiller optimizations where minuscule variance impacts
validity.
Regulatory Compliance Note
The resulting accuracy profile falls substantially below the strict ±0.05°C overall
uncertainty threshold required by the Singapore Government for chiller-plant efficiency
characterization and Green Mark compliance verification.
- Long-term stability: automatic self-recalibration cycle every 4 seconds to
eliminate operational drift and cancel analog measurement offsets.
- Enhanced Delta-T precision: all channels share identical internal reference
resistors, giving superior absolute matching for heat-flow metrics.
- Tailored transducers: individually calibrated thermistors optimized for Chilled
Water (CHW, 5–18°C) or Condenser Water (CDW, 26–38°C) ranges.
Hierarchical Differential I²C (dI²C) Bus Topology
Standard I²C networks are physics-constrained to a few centimeters. The AccQ converts to an
active differential-I²C interface, deploying digital sensors many meters from the chassis over
inexpensive Category 5e cabling. A proprietary hierarchical address structure maps a distinct
address space to each physical port, preventing collisions and allowing identical base-address
sensors to be polled independently. Using an external AccQ Hub, each base port extends 8-fold —
enabling up to 32 environmental sensors (Relative Humidity, Air Temperature, Air Velocity,
Static/Differential Pressure, and CO&sub2;).
Industrial Modbus-RTU Integration
- Local RS485 Master Port: high-speed direct local polling of high-frequency
instruments such as electromagnetic inline water flowmeters.
- Isolated RS485 Master Port: comprehensive galvanic isolation protecting core
metrology against ground loops and floating noise from distributed electrical power meters.
3 Edge Processing & Communication Matrix
The internal 32-bit microcontroller acts as an edge gateway. On power-up it polls the module
backplane, identifies active cards, and parses customized scaling maps from non-volatile storage.
Beyond aggregation, the controller performs localized thermodynamic math to output instantaneous
Heat Flow (kW) and operating efficiency (kW/RT) without burdening the site BMS. An embedded
interactive Configuration Manager lets technicians label channels, map Steinhart-Hart thermistor
coefficients, and structure flexible register-mapping blocks.
- Local / Cloud network links: simultaneous transport over 10/100 Ethernet or
integrated Wi-Fi.
- BMS integration layer: operates as a Modbus-TCP Server/Slave for SCADA or
building-control interrogation.
- Secure cloud streaming: telemetry frames via MQTTS secured with mutual TLS
(mTLS) client certificates.
- On-unit diagnostics API: lightweight RESTful Web API for rapid configuration
verification and local diagnostic dashboards.
