S90 TEMPERATURE SENSORS RESOLUTION
Figure 1 shows the position of the two temperature sensors in the S90. Both are standard 10K @ +25C.
The "Opt" sensor is on the outside of the lens assembly, and appears in the logical position. It accurately reports ambient temperature in CHDK. However, on the S90 (and likely S95), the "CCD" sensor is actually located on the PCB, as shown in the left panel. I measured its actual temperature with an IR thermometer going from PUP to full hot over 10 minutes, in REC MODE. The temp range was +25C to +47C, and CHDK followed my thermometer degree-for-degree. This is a very useful real-time measurement for once the imager gets installed.
Thus we can conclude that the OSD "CCD" reading in CHDK for this camera is actually the temperature of the PCB near the CCD connector.
So for the 101a, I attached the "Opt" sensor to the CCD instead (not pretty but functional, Fig 2) and now the IR thermometer (measuring the CCD surface) accurately agrees (ie, a step in the OSD when hitting 0.5C mark on the thermometer) with CHDK OSD "Opt" over a tested range of +18C to +30C, so far. Hence the CHDK now reports actual CCD temp on 101a.
QUESTIONS (reyalp?) ...
Q1. Can you give us one decimal place (the thermistors are accurate, but more, I can see stability), for example, Opt: -10.3, and format an explicit plus sign so that temperatures above zero show as eg CCD: +38.7 (it just looks more elegant). Not many folks know this, but one can write this C format string: "%+.1f" to display an explicit plus.
Q2. Is there a way I can change the text, e.g. instead of "Opt" write "CCD", and change "CCD" to "CKT", for example?