Field tools that work with no signal
Eighteen calculators, checkers and lookups for building automation work. Free, no signup, and everything runs in your browser — once a page has loaded, it keeps working in a mechanical room with no bars.
Tip: open the tools you use most before you head into the building, or add them to your phone’s home screen. They’ll work offline once loaded.
Protocols and data
Modbus 32-bit Register DecoderTwo registers in, all four byte orders out. Settles “why is this float garbage” in seconds.Modbus Address Converter40001 or offset 0? Convert between the conventional address and the zero-based offset actually sent on the wire.Modbus Exception CodesWhat each Modbus exception code actually means, and what to check when you see it.BACnet Object Identifier Encoder / DecoderSplit a raw 32-bit BACnet object identifier into type and instance, or pack them back together.BACnet Object Type CodesEvery BACnet object type code, searchable — for Wireshark filters and raw identifiers.BACnet Error, Reject and Abort ReasonsError, reject and abort reasons with what each one usually means in practice.
Networks
BACnet Config CheckerPaste a device list. Finds duplicate instances and MACs, baud mismatches, MACs above Max Master, network number conflicts and BBMD needs.Can These Two Devices Talk?Two IPs and a mask — same subnet or router required, plus what that means for Who-Is discovery.BAS Port and Protocol ReferenceDefault ports for BACnet, Modbus, OPC UA, Fox and the rest — for firewall requests and port scans.
Signals, sensors and drives
4–20 mA and 0–10 V ScalingSignal to engineering units and back. 4–20 mA, 0–10 V, 2–10 V, custom ranges.Slope-Intercept Calculator (y = mx + b)Pick your panel type — Siemens, JCI, Schneider and more — or go custom, and get the exact m and b your controller wants.RTD and Thermistor ConverterOhms to degrees. Exact Callendar-Van Dusen for Pt100/Pt1000, beta equation for thermistors.VFD Speed Scaling ConverterCommanded 60 and got 6 Hz? Convert between Hz and whatever raw format your drive actually expects.Three-Phase Motor Power & %FLAVolts, amps and power factor to kW, shaft horsepower and percent of full-load amps.
Air, water and units
Mixed Air and Outside Air FractionThree temperatures tell you your real outside air percentage — and whether the damper is where it claims to be.Hydronic BTU / GPM / ΔTAny one of BTU/hr, GPM or ΔT from the other two, with a glycol correction factor.Fan and Pump Affinity LawsSpeed change to flow, head and power. The arithmetic behind every VFD energy argument.BAS Unit ConverterTemperature, pressure, flow and power conversions, limited to the units that actually come up in BAS work.
Spot a wrong number? Tell me and I’ll fix it: svdraper@basfieldreference.com
New tools by email
Sent when a new calculator or reference goes live.