MISSING U1 in ULPSM Spec Sensor O3

We’re having a problem in the Spec Sensor readings the readings are too high which are above the standard limit.

After examining the ULPSM design and comparing it to our actual board, we discovered that a component, specifically U1, which is intended to be a precision voltage regulator, was missing.

We check the other board and unfortunately they have the same problem missing U1.

  1. ULPSM-CO 968-001
  2. ULPSM-SO2 968-006
  3. ULPSM-O3 968-046
  4. ULPSM-NO2 968-047


Please observe on the schematic that the footprint for the U1 voltage regulator is bypassed using a zero ohm resistor, R12. The U1 footprint is provided to simplify addition of a voltage regulator if a user so desires, but is not intended to be populated as delivered from the factory. You may notice that R7 and U4 are not populated either. Similarly, these component placements permit easy modifications to the boards in ways that the designer imagined that some might find useful, but are not intended to be populated from the factory.

Please note that the output of the sensors/ULPSMs requires calibration.