Engineering Constraint
The installation must collect multiple analog sensor signals located approximately 100 m to 400 m from a Revolution Pi system and publish the resulting data to the cloud through MQTT. The proposed central hardware is a RevPi Connect with one AIO card, but the evidence does not identify the sensor output types, signal ranges, wiring, accuracy requirements, or number of channels.
The supported design rule is to perform analog-to-digital conversion near each signal source. Carrying unconverted analog signals over the full distance can introduce measurement inaccuracies; the available evidence does not quantify the expected error or establish an acceptable maximum cable length.
Recommended Measurement Architecture
| Architecture | Conversion location | Decision |
|---|---|---|
| Central AIO card with direct sensor wiring | At the RevPi enclosure | Leaves each analog signal on a 100 m to 400 m run and conflicts with the stated guidance to convert near the source. |
| Distributed acquisition | Near each sensor or local sensor group | Preferred approach because the long-distance portion carries converted data rather than the original analog measurement. |
A single centrally located AIO card cannot also perform conversion near several widely separated sensors. Use local analog acquisition points and return the converted measurements to the RevPi through a suitable data link. The evidence does not specify the remote acquisition hardware, link protocol, media, or topology, so select those only after defining the site requirements.
Selection and Implementation Procedure
- Inventory every sensor, including its location, analog output type, required channel count, and measurement accuracy. These details are currently unknown and determine whether sensors can share a local acquisition point.
- Group sensors by physical location and place analog-to-digital conversion near each source or local group.
- Select a remote data transport compatible with the local acquisition equipment and RevPi Connect. Do not assume that the AIO card alone provides the required remote connection.
- Map the received digital values into the RevPi application, then publish the required measurements through MQTT.
Commissioning Verification
Compare each value at the RevPi with a known measurement at the corresponding sensor or local acquisition point. Test channels individually before enabling MQTT publication, then confirm that each cloud value retains the correct sensor identity and follows changes at its source. If a discrepancy appears, determine whether it exists before digital conversion, during remote transfer, inside the RevPi mapping, or in MQTT publication.
FAQ
Can one RevPi AIO card connect directly to sensors 100 m to 400 m away?
Direct connection would leave the analog signals on 100 m to 400 m cable runs. The supported recommendation is to perform analog-to-digital conversion near each sensor source to avoid signal inaccuracies.
Where should analog-to-digital conversion occur in a remote RevPi installation?
Place conversion near each sensor or nearby sensor group. Transfer the converted measurements over the long-distance link to RevPi Connect.
Can RevPi Connect publish distributed sensor measurements through MQTT?
The stated requirement is to publish the collected data through MQTT. First verify each converted value and its RevPi mapping, then confirm that the corresponding MQTT value changes with the source measurement.
