Accuracy in Design

What is the best method for tightly controlling accuracy in your design?

Step 1. Determine the scope of the problem

1. Start with defining what you need to control (i.e. what output, what variable).
2. Then proceed to work out the flow of that output from beginning to end. Basically form a block diagram of components/stages/circuits.
3. For each stage identify the sources of error or perturbations for each.
4. Form functions (even if qualitative) for each stage. Each stage output should have all inputs, desired and undesired, as an input. The final output should be a function of all the other stages. Each of these is a part of the output function. An error in these is an error in the output.
5. Quantize these variables and determine which have a greater impact on the output. Now we are in a position to control the output.

Step 2. Design out the variation

1. Don't black box the design. Brainstorm different solutions/technologies to see which is a better fit. A more sophisticated design that has feedback loops or other techniques will make the design less susceptible to environmental change.
2. Choose individual components that are less susceptible to environmental change.
3. If that isn't possible then control the environment (e.g. temperature control, etc)
4. Your last hedge is calibration. Calibration is allowing error and compensating for it after the fact. If you can measure the real response to the worst environmental variables and introduce compensation in your circuit / software / hardware you can offset the effects.