LW, The best way to consider solutions for logging a roast is to segment each of the 3 core components needed in order to achieve your objectives. 1. Sensor - thermocouple 2. Bridge - device transducer or I/O conversion appliance 3. Graph software What I suggest you do is research the various options available in each of these components so that you arrive at the solution that best suits your needs - cost, complexity, reliability, quality of end-result. I've been logging roasts for such a long time on numerous platforms - well before it became a trend for coffee roasters. A background in electronics, process control, industrial and IT engineering helped drive the desire from the beginning. Each topic requires research as there are many choices and decisions to be made. Something as simple a probes - type, grounded, shielded, thickness, length (for both probe and cable), response time, etc. all influence the sort of results, accuracy and stability of the solution. As a general rule, stick with thinner, K-type probes that are more responsive, but placement is the most critical design element. Be careful to ensure the positioning will record the appropriate readings from the target source and that it's reliable and consistent so that observed and developed reference points have some form of reliable integrity. Also be careful that probes don't get damaged by agitation or operation. Bridges are a keenly debated topic. You can start with something simple like an advanced multi-meter or take a DIY path with an Arduino. There are a myriad of possibilities, but what you need to look for is making sure the bridge works reliably, does not "hang" or "freeze" at the worst times and that noise and interference (EMI) are managed. The purpose of the bridge is to convert the resistance changes detected by the thermocouple into signals and output via USB ports that can be fed into graphing apps. Some bridges come with multi-ports that enable you to capture the environment temps or even ambient temps as well as bean temps, so this can significantly aid the roasting process as you can do things such as monitor the air temp around the bean mass and detect when it starts to drop as a leading indicator the bean temps (or Rate of Change) will stall or fall. The key to a good bridge design is for the USB connection with the computer to be robust and reliable - a critical weak link in apps many years ago. Graphing software is the business-end of the equation. Here is where it translates into something that gives you all the important insights. What you need to look for in the application is an ability to "smooth" curves and plot lines without hiding real or valid changes ( dumbing it down ). Although nothing is worse than using graphing software that plots jumpy graphs looking like those old-fashioned seismographs with erratic lines everywhere. You need to be able to scale the graph so that the temperature ranges for your probes are drawn easily, there needs to be are features like large displays and averages for Rate of Rise, etc. The best apps overlay the graphs for bean and air temps with the RoR so you don't need to flick back and forth. Artisan is an excellent roast scope application and it's device support is wide. There are also similar apps like RoastLogger, etc. and more are coming onto the market - most are free. My pro tip....... Don't get too hung up on what temps your solution is recording by comparing it to others. Just because one person might achieve turning point at say 90 deg C and yours it at 100 C, does not mean something is wrong. Each installation is a little different and the probe implementation makes all the difference. Just ensure that you see a good range of temps between turning point and finish temp so that you know your probe is recording as close as possible the actual or likely real bean temps. Obviously, the design of your vessel and the way in which you roast make a big difference, but let's say for example you should see maybe a low of 100 C and typical dump temps of 209 - 215 C for coffees roasted just before 2nd crack. On one of my many roasting plants I use a Cropster bridge feeding Artisan and it works a treat. I prefer to use that solution over the vendors automation package because some roaster manufacturers have no idea. My manual workaround is simple and hard work but I can beat the vendors algorithm every time.....who said humans are becoming obsolete. On other systems it’s more complex like control of burner, drum, air, destoner, cooling, etc. in configurable steps. In our most advanced platform which is the best available (and seriously expensive), it can roast according to desired curve which is insanely geeky and cool, nothing else on the market can match this functionality and it’s like the next generation technology that very few people are using......which is surprising. In summary, it’s my firm opinion that you cannot roast high quality with consistency by relying upon olfactory senses. I qualify this by stating it gives you a great foundation understanding but its significance is overrated - by the time you have sensed or seen something it’s too late. It’s fundamentally critical to see everything at all times and this is only possible with data logging - the single most important contributing factor why coffee quality has spiked so high in the last decade, roasters can see what’s going on instead of relying upon sight and smell.
