Nuts and Volts - February 2016

only requires one pin for interfacing. The board is so easy to use that a manual isn’t even required. All the necessary information is printed on the back of the board (see

Figure 2). We’ll get into the details when we begin our experiments this month, but there’s one thing I want to mention at this point.

Because the board provides an analog output, interfacing it with a PICAXE processor is almost identical to the MCP9700A based temperature measurement project we covered back in the December 2012 issue of Nuts & Volts. As a result, if you have no interest or need to monitor any temperatures higher than 257°F, you can easily substitute an MCP9700A sensor for the AD8495 board and thermocouple sensor in any of this month’s experiments. The only software change would be to edit the portion of the software that converts raw ADC ( analog-to-digital converter) input to degrees Fahrenheit, so that it matches the one we used in the original MCP9700A project. Also, the techniques we’ll be using to record and display data can be readily applied to just about any data logging project you may want to implement.

The AD8495 printed circuit board (PCB) can be used with any K-type thermocouple sensor. This type of sensor is readily available on the Internet, but I chose one from Auber Instruments (see Figure 3 and Table 1) because its physical dimensions suited my requirements and it can measure up to 900°F, which is sufficient for my application. The Auber thermocouple comes with two standard spade connectors that can easily be removed, so the probe can be directly connected to the Adafruit thermocouple amplifier board.

However, when I ordered the probe, I also ordered a pair of thermocouple connectors — one of which is a female panel-mount connector (see Figure 4 and Table 1) because I plan to eventually mount the electronics inside a plastic project box. Also, the male connector fits into the standard female connector on one of my multimeters, so I can use the probe that way as well.

Experiment 1: Using a Thermocouple to Measure Temperature

In this experiment, we’re simply going to test the thermocouple interface to make sure it’s functioning correctly. The schematic for the experiment is presented in