# [time-nuts] Fury - Rubidium

SAIDJACK at aol.com SAIDJACK at aol.com
Wed Jul 28 01:52:05 UTC 2010

```Hi John,

on the Fury, the proportional part you describe is roughly the same as EFC
Scale. The integral part is PHASECO.

Fury can happily run with correct frequency output with PHASECO set to 0,
but the phase offset would be large, and slowly changing over time.

The EFCS (proportional part) makes sure the frequency is correct, and the
PHASECO (integral part) makes sure the phase error is "integrated out" to
0.0ns.

hope that helps,
bye,
Said

In a message dated 7/27/2010 18:37:20 Pacific Daylight Time, jfor at quik.com
writes:

> I  read the article on PID on Wikipedia last night.  I do not fully
>  understand it, but I see/learning some of the relationship.

Here's a  very quick primer:

Consider a very simple control position servo  loop:

Pos. Input --- + (SUM)--- PID --- AMP > --- MOTOR =====  Output Pos
|-                   ||
|          POS Sensor
|                 |
-----------------------------------

If you put an upwards step into  the Pos Input the output of the SUM goes
up. This is applied to the AMP via  the PID network and the MOTOR stasrts
up, turning the output shaft. As the  Output shaft turns, the position
sensor output rises. That subtracts from  the commanded position in the
SUM, reducing the AMP input.

Thats how  the P = Proportional signal drives the loop to null.

However, in order  for the motor to turn some non-zero voltage needs to be
applied. As the SUM  output approaches zero the motor drive ceases and the
loop never reaches  null. So the I = Integral term is added. If the loop
stops just shy of  null, the SUM output will not be zero. The I Integrator
takes the near-null  voltage and integrates it (Vsum dT) which will
eventually rise sufficiently  to drive the motor to null.
```