[evlatests] Updated T304 Auto Level Control Software

[Keith Morris]

A trial version of the updated ALC controller software has been loaded 
onto ea25-t304-a and ea25-t304-c.

When a new TPD target is set, the ALC controller will issue one coarse 
step the first second, then fine-control steps at the rate of 1dB per 
second until the target error is < 1dB.

If the target is invalid, beyond the range of the step attenuators, an 
"invalid target" message will appear in the .msg field of the TPD 
monitor point, and the attenuators will subsequently fail to achieve the 
target.

Due to some nonlinearity in the response of the step attenuators, there 
is typically 1-2dB of overshoot (or undershoot, perhaps), which is then 
corrected by the fine-step control loop.


-- 
Keith Morris
National Radio Astronomy Observatory
phone: 505-835-7060
fax:   505-835-7027