Boosts - C/min vs %/min

[Luca]

I would like to make sure I understand how "boosts" work

The software says "Default: 0 (degrees C/min or %)"

Does this mean that:

A. If you have zone multipliers not equal to zero, the "boost" changes the number of degrees per minute over that zone. (This is a per minute change, so if it's set to 5 and the zone is 2 mins long, you will get a boost of 10C.)

B. If you have zone multipliers set to zerio, the "boost" changes the the percentage power over the zone. (This is a change over the entire zone, so if it is set to 5 and the zone is 2 mins long and you begin the zone at 1000w, you will get to 1025W at the end of minute 1 and 1050W by the end of the zone.)

???

[Geronimo]

Hi

Have you had a look in the companion manual?

https://kaffelogic.com/downloads/manual ... on%203.pdf

Cheers

[Luca]

Yes, I checked that, I'm asking because I want to confirm.

[Geronimo]

Yes, I checked that, I'm asking because I want to confirm.

No worries.

[kaffelogic]

I would like to make sure I understand how "boosts" work

The software says "Default: 0 (degrees C/min or %)"

Does this mean that:

A. If you have zone multipliers not equal to zero, the "boost" changes the number of degrees per minute over that zone. (This is a per minute change, so if it's set to 5 and the zone is 2 mins long, you will get a boost of 10C.)

B. If you have zone multipliers set to zerio, the "boost" changes the the percentage power over the zone. (This is a change over the entire zone, so if it is set to 5 and the zone is 2 mins long and you begin the zone at 1000w, you will get to 1025W at the end of minute 1 and 1050W by the end of the zone.)

???

The Kaffelogic roast control system measures the rate of rise, and compares this to the rate of rise needed to keep the roast on track (or get it back on track). The controller error is measured in rate of rise (deg/min). This is different from 'conventional' PID control that measures temperature, and compares it to the current temperature from the profile curve. In that case the controller error is measured in temperature (deg).

Based on the amount of error detected the control system applies a change to the power level.

A boost is a constant amount of rate of rise (deg/min) that is added to the error in every calculation cycle. In the Roaster's Companion I have compared this to steering slightly to one side of a target when sailing a boat across a river. Why would you do this? In a boat you would do it because there is a current flowing across your bows and you are compensating. In effect you are pretending that you are off course by a consistent amount to compensate for the current.

It is reasonable to expect that a boost of 5 deg/min for a 2 minute zone should result in a gain of 10 deg compared to the same roast without the boost. But actually if the boost pushes the roast above the profile line, this creates an error in the rate of rise in accordance with the control system adjusting to get the roast back on the line. The boost is effectively diluted by this. It will work to compensate for the beans going endothermic or exothermic, but its effect will be diluted the further the roast departs from the profile. So in the end a boost of 5 for 2 mins might result in only a couple of degrees overall difference by the end of the zone. This is why you often find you need more boost than you think you need to achieve something specific.

You description of power profiling is correct.

Cheers
Chris

[Luca]

Thanks, Chris.