Moku:Pro LLB Slow Control bugs in MIM

Support & Troubleshooting
1

Moku model: Moku:Pro
Operating system: any
Software version: v3.0.0b1181 (firmware 580)

Bug or support request description:
We are using a Moku:Pro as a laser lock box instrument in Multi-Instrument mode and are witnessing some very strange behaviors with the slow control path of the instrument.

  1. When the laser lock box is used in MIM with a variety of other instruments in other slots (specifically in our case, we had LLB in Slot1, PID controller in Slot2, Digital Filter Box in Slot3, and Frequency Response Analyzer in Slot4. When used in this configuration, the output of the slow control PID is always giving a triangle wave ramp signal. No matter how many times we tune the instrument or reset the configuration, the slow control output is ALWAYS sending out a ramp. This issue disappears when the LLB is used in MIM alone in Slot1.

  2. We cannot understand how the output rails, or limits, are set. We operate LLB with slow control being sent to the temperature of a laser. We record the value of output 2 during operation and we notice that the temperature output “rails” or achieves a maximum (or minimum) flat value even when limits are turned off for Output 2, and stays there thereafter. However, these rails are in locations we would not expect, for example at +15mV and +8mV for the high and low limits, respectively, when operated with a +11.5 mV offset.

Therefore it appears to us, that the limits are set somehow relative to the offset (in this case, +/- 3.5 mV around the offset), and not to the maximum output range of the Moku:Pro itself. Additionally, we suspect that the output range is related to the coefficients we apply to the slow control PID - for example currently we apply a proportional gain of -50dB which is a linear scaling of 0.0032 - applied to the output range of +/- 1V, this corresponds to the ~3.5 mV we are seeing.

In summary, we suspect that the LLB slow control output range is limited by the proportional gain of the slow control PID. We would much rather take advantage of the full +/- 1V output range we set.

Cheers
Todd