SUNA V2 Humidity Bulletin: Humidity ingress and sensor performance

Humidity quality issue:
The SUNA V2 can suffer from rates of humidity ingress which can ultimately result in premature sensor degradation or failure. Humidity ingress is first exhibited as spectrometer noise followed by potential spectrometer and/or electronics failure. Most failures are experienced in low pressures, high temperatures, and extended continuous deployment régimes.

Intermediate solution:
We ask our customers to monitor humidity so sensors can be sent in for purging and repair before the humidity causes data quality concerns or permanent damage.

Final solution:
The solution is a new titanium housing design which is water impermeable, while providing structural strengthening, and improved hermetic sealing. This upgrade will be available to our affected customers free-of-charge. Sensor performance specifications are unaffected by this change.
The SUNA V2 transition to titanium housings will increase its weight by ~0.6-kg and change the appearance from black to shiny. Price will remain the same. While annual service is still recommended to ensure quality nitrate measurements, most scenarios will allow greater than 18 months of deployment.

When is the solution available?
The upgrade is currently available. Sea-Bird Scientific will provide the upgrade to affected SUNA V2 sensors until July 1st of 2017.

How fast can you get your SUNA V2 back?
We realize that monitoring season is starting soon (or ongoing) and you need the fastest service times possible. Our goal is a 4-week servicing turnaround time. Please work with our customer service representatives as we prioritize upgrades for customers with instruments with high rates of humidity ingress. If your SUNA has come in on an RMA for another reason, it may be upgraded if it is found to be affected.

How much does it cost and who is eligible?
The price of a SUNA V2 with these new upgrades will not increase. Sea-Bird Scientific will cover the costs of shipping current SUNA V2s (both ways) and costs for upgrading and calibration. To assess the present humidity condition of your SUNA and determine whether it needs the upgrade, we have provided an Advanced Test through the SUNACom software, described below. The test can determine if the instrument is affected by the issue before data quality suffers. The upgrade will be provided on a priority basis to the most urgent cases for affected SUNA V2 instruments as determined by the test. If you have not encountered the issue, it is unlikely you will be affected. To receive the upgrade for your SUNA V2, your SUNA V2 must have been built or serviced in 2014 or 2015.

If your sensor needs additional service either our standard service or more specific service (e.g., lamp replacement) will be quoted.

Important things to do now, how to know if you may be affected, and what to do:
SUNAs in the serial number range of 199-810 may be affected. If your SUNA is within this range, look for the symptoms described below, run the self-test, and contact if you need assistance. If your serial number is not in the stated range or if you have a Deep SUNA, no further action needs to be taken.

Evaluating your SUNA for humidity ingress:

Humidity in SUNA V2 increases over time causing spectrometers to exhibit high dark noise and fail the humidity self-test. To know if you are affected:

1. With your SUNA V2 connected to SUNACom, run the Self Test feature.

2. If the test fails for humidity or dark counts, please run the advanced test described below (in certain cases, the self-test can result in false positives).

3. If the advanced test passes, continue to monitor your SUNA V2 with self and advanced tests at your regular service intervals.

4. If the advanced test fails, please contact and provide the test result data.

Humidity increases could be exacerbated by higher temperatures and pressures, mechanical mounting that squeeze the housing out-of-round or those that create bending force along the long axis of the SUNA.

Advanced test:

  • Step 1: Using SUNACom software:
    • 1. Go to the “Sensor” drop-down menu in the upper right hand corner.
    • 2. Hover over the “Advanced” option.
    • 3. Select “SUNA Self Test.”

      SUNA Operators running a SUNA Self Test may see an '!' in the spectrometer dark test, and an $Error 1 response at the end of the output. The result of the Self Test is meant to alert that a more comprehensive test should be executed to properly evaluate the spectrometer and if the relative humidity in the SUNA exceeds 50%. The (!) alert is spurious if the spectrometer dark noise value is <=9 AND the dark max-min is <80. Otherwise, we recommend the following comprehensive test.
  • Step 2: Collect spectrometer dark data using SUNACom software:
    • 1. SUNA Settings -> General Tab:
      • Continuous Operating Mode
      • Frame Based
      • Light Frames: 1 Dark
      • Frames: 5000
      • Sampling Average: 1
      • Disable Wiper (if present)
    • 2. SUNA Settings -> Telemetry Tab:
      • Set frames to FULL_ASCII
    • 3. Start Data Acquisition
    • 4. Log 15 minutes of data to a file
  • Step 3: Contact Support at with instrument information and a copy of the Data Log file at for evaluation.