Temperature Sensor Board Stability and Fix
A few weeks ago one our builders commented to us that the Temperature Sensor Board (TSB) installed in a recently built organ, was not stable in the firsts 10 minutes of power turn on. Apparently, in the first 10 minutes of use, the data value the TSB was outputting was rising about 10 points. This meant that it took 10 minutes before the electronic voices would be in tune with the pipes.
This was the first we had ever heard of this problem. The builder was surprised we hadn't heard of the stability issue, apparently he had talked to some other builders and they all said this was a known issue with the TSB. Seems a few people have know about this, but none of them had ever mentioned it. Lesson to be learned here, if we don't know there is a problem, we can't fix it.
I spent quite a lot of time over several days experimenting with this board. Whenever we needed to test the TSB, we would plug it in, measure the values, hold the sensor in our hand to heat it up, see the values change and know the board worked. We never bothered to leave it running for an extended period of time.
The sensor on the TSB is fairly close to the chip on the board. What I found while testing was that if the board was mounted vertically, so heat from the chip rose past the sensor, I got a significant value change over the first few minuets. If I mounted the TSB so the sensor was down, and heat rose away from the sensor, I still got a value change but not as great. Regardless how I mounted the board, there was some change. What we needed was a heat sink.
We are now building the TSB so that the sensor is on really long legs, this is so you can bend it. When you put a TSB in an organ, mount the TSB next to a metal pipe, then bend the legs of the sensor over, so that the sensor part itself is touching the pipe. This pipe will now function like a heat sink, stabilizing the temperature of the sensor. This doesn't get rid of the value fluctuation completely, but it does reduce it significantly.
This picture of how to mount the TSB is courtesy of Jim Dodington.