Optimisation of the switchable gain amplifier gain

[JochiSt]

Instead of just testing various configurations, this problem can be optimised in a better way.

I did this using `scipy.minimize of a function, which calculates the integral (sum of all) temperature uncertainties. Some penalty terms are included to enhance the lower current sector.

• smaller 3.0mA gets enhanced by a factor of 10
• smaller 1.2mA gets enhanced by a factor of 50
• if the maximal overall temperature uncertainty is larger than 1K the whole sum gets multiplied by 100. This is to force a resolution better than 1K everywhere. (Especially the gain switching points are pronounced to this issue).

    sT = np.where(a_Istim < 3.0e-3, sT_raw * 10 , sT_raw)
    sT = np.where(a_Istim < 1.2e-3, sT_raw * 50 , sT)    # no self warming

    if np.max(sT_raw) >= 1:
        return np.sum(sT) * 100

    return np.sum(sT)

[JochiSt]

From this study, the best resistor values for the switchable gain amplfiier are:

U channel:

• R1 = 330k
• R2 = 56k

I channel:

• R1 = 470k
• R2 = 56k

Note: only R1 was optimised during this study. R2 has been fixed at 56k.