NEW THERMOMETER   

Originally, temperature was measured with an Analog Devices AD590 temperature transducer connected to a dedicated ADC that drives a dedicated LCD (recall the Intersil 7106). This setup had worked flawlessly for several years, but I felt it was time to integrate temperature measurement into the weather station’s Freescale Semiconductor MC68HC11E1CFN2 microcontroller.

I had tested a variety of serial temperature sensors, and the Maxim DS1624 was my favorite. However, its serial interface didn’t lend itself to the MC68HC11E1CFN2. I implemented the DS1624 interface in software, but it took some effort. In addition, I was concerned now that the weather vane needed to be sampled every 10 ms. So,even though I had planned on using a DS1624, I ended up going with a National Semiconductor LM95071 temperature sensor, which is a 13-bit plus sign unit made specifically for a SPI. Temperature measurements are done quickly. (Note that Figure 3 was drawn for a DS1624 because I haven’t tested the LM95071.)

The thermometer is mounted in a small ventilated box on the weather station’s pole. I didn’t include a photo because there isn’t much to show.