Page 18 - Customer Needs and Use Assessments (CNUA) of pH Sensors

ACT In Situ pH Sensors Customer Needs and Use Assessment............................................................................ 17
23. Relative to the above (Questions #21 and #22) sensor system characteristics, are any of your sensor
needs or requirements “non-standard” or custom made? If yes, please describe.
Yes : 18.9 % (7)
No: 81.1% (30)
Four respondents left comments. Two recognize that ISFET sensors could have a greater working depth for
profiling applications, and those systems that do work at depths greater than 500 m are hard to find and thus
mostly nonstandard. Another respondent uses an ISFET pH system that has been augmented with custom
electronics allowing an external reference sensor. These systems are built in the laboratory of an academic
colleague. Another non-standard sensor requirement is the need to develop protocols or calibration standards
that would allow easier pH measurements across changing ionic strengths. A final sensor need that is non-
standard involves mounting in situ pH sensors on non-standard platforms (such as on plankton nets).
24. Are you happy with your present pH sensor?
Yes : 47.4 % (18)
No: 52.6% (20)
25. Do you plan on acquiring new commercial sensors within the next 2 years?
Yes: 75.0% (30)
No: 25.0% (10)
Nineteen respondents of the 30 who said that they do plan on acquiring new commercial sensors went on to
answering the following question:
If yes, will you consider a different sensor type than the one you are currently using to measure pHs?
Fourteen respondents said yes; two on the condition that the different sensor type still fit either their existing
sonde or CTD. Two respondents were decidedly not happy with their existing potentiometric sensors and were
searching for new technologies and/or manufacturers. One respondent is looking specifically for better accuracy
and precision so they can actually use their data. The remaining respondents were in large part imply interested
in trying out new sensors and trying to find something better, particularly those pH sensors employing
spectrophotometric and ISFET technologies, or they were purchasing multiple field-deployable sensors and
perhaps could afford to evaluate other sensor types. Finally, two respondents specified that any newer model
be based on field robust design with increased reliability, rapid response and the capability of operating over a
good depth range. Both specifically cited sensors built around a small form-factor response; one user cited the
smallest form factor for use on a mobile sensing platform (AUV).
Five respondents said they would not consider a different sensor type than the one they are currently using to
measure pH. Reasons include the fact that their current sensors work well, particularly those favored to be used
in seawater. This group tended to use ISFET technology and is pleased with the accuracy and stability these offer.
One respondent is very happy with the group that is helping design their sensors.