Solution
LRV is acronym for Lower Range Value while URV is acronym for Upper Limit Value.
LRV and URV are set by modifying block parameters:
XD_SCALE (e.g., -50 to 150 °C): This sets the physical range of the sensor input.
OUT_SCALE: This defines the engineering units and the display range.
Steps in NI-FBUS Configurator:
- Open the device block (AI, AO, etc.).
- Find XD_SCALE and OUT_SCALE attributes.
- Enter new High and Low values manually.
Tips: Some devices also allow setting alarm limits (e.g., HIGH_HIGH, HIGH, LOW, LOW_LOW) for process monitoring.
Unit conversion is typically managed in the OUT_SCALE parameter:
OUT_SCALE.UNITS defines the unit type (e.g., degrees Celsius, psi, %RH).
You can change the engineering unit code based on the Fieldbus standard (ISA SP50 standard units). Adjust the SCALE values to reflect the new unit (e.g., from °F to °C, adjust the scale accordingly).
If native unit conversion is not available. You can create a Transducer Block or custom logic in the Host System or LabVIEW for scaling (e.g., °F = (°C × 1.8) + 32).