AccQ Series · End-to-end certified
Certified accuracy for HVAC systems
The AccQ system provides all your HVAC measurement and control needs into a single integrated system. It combines highly accurate water temperature measurements with air temperature & RH, differential pressure and CO2 concentration measurements using our range of custom sensors. It receives readings from external Modbus instruments. All these measurements are integrated to supply the key parameters of the HVAC system in a language understood by the BMS, the building manager and efficiency optimisation systems.
Key specifications
| Parameter | Specification | Notes |
|---|---|---|
| Device measurement uncertainty | ±0.0022 °C equivalent @ 10 °C | Resistance readout accuracy (±0.01 % ±0.25 Ω) expressed as temperature, before any probe uncertainty budget; auto self-recalibration every 4 s |
| Matched-pair ΔT tracking | ±0.02 °C (pair)* / ±0.03 °C (abs)* | Pairs are matched for ΔT accuracy across the operating range (CHW 5–18 °C, CDW 26–38 °C), tighter than two individually calibrated probes |
| Precision thermistor inputs | Up to 24 channels | 1–4 PTT modules × 6 channels each |
| Environment sensors | Up to 32 devices | A wide range of sensors measuring air temperature & RH, CO₂ concentration and differential air pressure are available, operating up to 30 metres from the AccQ unit. |
| Supported protocols | Modbus TCP, MQTTS, API, webhooks | Integration with BMS or other external systems via Ethernet or Wi-Fi; some external integrations require the control plane |
| Field instrument ports | 2× RS485 Modbus RTU master | Modbus RTU master for field instruments; 1× galvanically isolated; 9600–38400 bps; up to 16 downstream units |
| On-edge computation | Heat flow (kW), efficiency (kW/RT) | Reporting interval 4 s to 36 h, true time-averages |
| Power & chassis | 110–240 V AC, 50/60 Hz | 185 × 100 mm; width 150 mm (3-slot) or 300 mm (6-slot) |
*Anticipated accuracy, subject to final laboratory report. Abridged from Technical Datasheet Rev 3. Up to 24 thermistor channels and up to 32 dI²C sensors per unit.
Modular by design
Slot-in modules on a shared backplane. Size the chassis (3 or 6 slot) to the plant, not the other way round.
ACCQ-PWR power
110–240 V AC input with regulated 7 V / 5 V / 3.3 V rails. One supply for the whole chassis.
ACCQ-CON connectivity & control
4× dI²C sensor ports, local + isolated RS485 Modbus RTU, Ethernet and Wi-Fi. Runs the Modbus TCP server, MQTTS telemetry and on-edge computation.
ACCQ-PTT precision thermistors
6 four-wire channels per module (Cur / Sen / Shield) for calibrated, matched-pair thermistors. Up to 4 modules, 24 channels per chassis.
Sensor array + AccQ Hub dI²C ecosystem
Digital temperature and humidity sensor arrays connect to the dI²C ports over standard Cat 5e. The AccQ Hub expands each port to 8 sensors, up to 32 per unit, for ducts, AHU coils and rack inlets.
How it connects
For chiller plant and AHU measurement, verification, and optimisation, see HVAC applications .
Technical datasheet · Rev 3
AccQ Series specification sheet
Full metrology, dI²C bus, Modbus RTU, and environmental specifications for the modular environmental monitor. Open in your browser, then print or save to PDF.