Pressure measurement is everywhere in vehicles, machines and energy systems: hydraulic lines, coolant loops, compressed air, fuel systems, intake manifolds, battery enclosures and hydrogen tanks. In many programmes, the harder task is getting pressure detection sensor data onto the CAN network where controllers and loggers can use it. There are two routes, and the right choice depends on the sensor and the job.
Route one: native CAN pressure sensors
The simplest option is a sensor that speaks CAN directly. There is no signal conditioning, no analogue input to allocate on a controller and no scaling to configure. The sensor converts pressure to an engineering value internally and transmits it as a CAN message.
Metis Engineering’s environmental sensors take this approach. Cell Guard, H Guard and Air Wise all measure absolute pressure from 0.3 to 1.2 bar alongside gas, temperature and humidity measurements, and Cell Guard and Air Wise resolve pressure to 0.0001 bar at update rates of up to 50 Hz. Each has a configurable CAN address and baud rate and ships with a DBC file that describes every signal, so the data can be decoded in standard tools the moment the sensor is connected.
Native CAN sensors are particularly suited to safety applications such as detecting battery cell venting or hydrogen leaks, where the pressure reading is most valuable when combined with other measurements in the same device.
Route two: converting analogue pressure transducers
Many pressure sensors in use today are analogue. Industrial and automotive pressure transducers commonly output a 0 to 5V signal proportional to pressure, and there are good reasons to keep using them: they are available in every pressure range and media compatibility imaginable, they are well understood, and they may already be fitted to the system.
The challenge is getting those signals onto CAN without dedicating scarce analogue inputs on an ECU or adding a separate data acquisition system. The Metis Analogue to Digital CAN Module solves this. It reads eight analogue channels at 12-bit resolution, measuring 0 to 5V in 0.003V increments at up to 333 Hz, and transmits the results over CAN. Any 0 to 5V pressure detection sensor can be connected, and its readings appear on the network alongside everything else.
The module also includes a 10k pull-down resistor on each channel, allowing resistance-based temperature sensors to be connected without extra components, and four channels that measure frequency and duty cycle for PWM signals. A single module can therefore collect pressure, temperature and PWM data from a mixed set of sensors. The A to D Connection Kit simplifies wiring during development.
Keeping power consumption low
Pressure monitoring often needs to continue when a vehicle or machine is switched off. A hydraulic accumulator losing charge, a coolant loop leaking or a battery enclosure pressure changing while parked are all events worth catching. But keeping a full controller awake to watch them drains the battery.
The Analogue to Digital CAN Module offers a low power sleep mode drawing less than 1 mA, with the ability to wake on voltage thresholds from a connected sensor. That means an analogue pressure transducer can be monitored while the rest of the system sleeps, with the module waking the CAN network if pressure moves outside a set window. Metis notes that the same feature makes the module useful as a vehicle CAN wake-up device triggered by a button press.
Native Metis sensors offer a similar capability. Cell Guard, H Guard and Air Wise all include a low power monitoring mode in which they watch the environment but only transmit on CAN once a threshold is crossed, at which point they can also toggle a 500 mA low-side drive output.
Getting the network design right
Whichever route is chosen, a few principles keep pressure data reliable. Configure unique CAN addresses for every device to avoid message conflicts. Set bus speed consistently across the network. Use the supplied DBC files to decode signals rather than hand-coding scaling. Terminate the bus correctly at each end; the Metis R&D Development Kit includes a switchable termination resistor with filtering to reduce noise for bench and prototype work.
Place pressure detection sensors where they see the event of interest. In a battery pack, that means near the breather path. In a hydraulic system, it may mean close to the component being protected rather than at a convenient manifold.
Combining routes on one network
Many real systems use both approaches. A battery electric machine might carry a Cell Guard in its pack for venting detection, an Air Wise in the cab HVAC, and an Analogue to Digital CAN Module reading hydraulic and pneumatic pressure transducers, all on the same CAN network. Add an 8 Channel Isolated Thermocouple to CAN module for high-voltage temperature measurement and a GPS CAN sensor for position, and a complete data picture is available through a single interface.
Validating the data chain
Before relying on pressure detection sensor data for control or safety decisions, engineers should validate the full chain from sensor to controller. That means confirming scaling against a reference gauge, checking that alarm thresholds trigger the intended response, testing behaviour when the bus is heavily loaded and verifying that wake-up from low power mode works as designed. Native CAN sensors and the Analogue to Digital CAN Module both make this straightforward, because every signal is defined in the supplied DBC file and can be inspected in standard tools.
Pressure data, wherever it comes from
The value of a pressure detection sensor lies in what the system does with its data. Getting that data onto the CAN network quickly and reliably, whether from a native smart sensor or a proven analogue transducer, is the first step.
To discuss integrating pressure measurement into your CAN network, contact Metis Engineering at info@metisengineering.com.
