Help for DigiPID
Version 2017-11-10

Overview

The webpage is in four sections: at the top are the operating parameters, in the middle is the setup (which probably never change once set), below that is a graph with a snapshot of current conditions, at the very bottom is a place to upload an output transfer curve.

In the middle (setup section), select which mode the unit is for: DC to run a external AOM driver or a laser driver, or RF for an external AOM amplifier. If RF output, set the VCO frequency. Select the VCO with the narrowest range which can work at the desired frequency.

Although possibly unclear, in Run box, the Target box shows as a voltage. Similarly, the graph showing output in RF output mode will show as voltage. IN DC output, these are obvious, voltage is voltage. In RF output it is less clear. The internal RF modulator runs between ±7.25V, approximately, where -7.25V is zero RF output and +7.25V is 100% RF output.



Webpage
Web verHTML, JS and CSS version
EmbeddedLeft: embedded, right: HDL
SavesNumber of times configuration was saved (max 20,000)
Configure - MonitorMonitor:Shows current state
Configure: Client changes parameters, must click Apply to implement
ApplyAppears in Configure, click to implement as shown
Save as defaultIf checked, will save as default power-up state, otherwise lost if unit is rebooted
Green/Red CircleGreen means connected to unit, red disconnected. Number shows how many clients currently connected
RunP gainProprotional gain, normalized to 100%
I gainIntegral gain, normalized to 100%
D gainDerivative gain, normalized to 100%
TargetThe voltage which the whole system is trying to maintain
CurrentlyThe current output level
ManualWhen Manual mode is selected, the output level, can also adjust on the unit directly
StopWhen Stop mode is selected, the output level
Pulse1FrequencyWhen Pulse mode is selected, the frequency of the pulse output
Duty cycleWhen Pulse mode is selected, the duty cycle of the pulse output
SaturationInputWhen lit, indicates an analog input saturation, reduce analog gain
OutputWhen lit, indicates an output saturation, reduce main gain
IntegratorWhen lit, indicates error integrator saturation, reduce I gain
Input
Parameters
GainAnalog input gain, increase until input saturates then reduce gain
BandwidthAnalog input bandwidth, also affects the processing rate (2.5 times oversampled)
ResistanceAnalog input resistance, with 50Ω do not exceed 3Vrms for >1 second
Output ModeDCThe DC output is active, all applicable parameters are in V (RF output is disabled)
RFThe RF output is active, all applicable parameters are normalized in % (DC output is still active)
DC
Output
Limits
MaxDC output only, the highest output voltage allowed, can be +ve or -ve but must be more positive than Min
MinDC output only, the lowest output voltage allowed, can be +ve or -ve but must be more negative than Max
RF FrequencySetThe target frequency for the RF output, when Active Lock selected
Meas.The measured RF output frequency
ControlThe control for the RF frequency. Manually set when Manually Set selected
Lock?2Either Actively Lock to find and keep the Target frequency
ChartNoneNo chart
OutputA snapshot of the current output, analog DC or RF level as applicable
InputA snapshot of the current analog input
Transfer3The output transfer curve in use
Output
Transfer
Curve3
Choose File4Select the ASCII text file defining the output transfer curve
Force LinearCheck to revert to a linear output transfer curve
Note 1:  In DC output, the pulse output swings between DC Output Min and Max, in RF output between 0% and 100%
Note 2: When Active Lock, the RF frequency will constantly adjust slightly up and down around the Target frequency
Note 3: See the section on the Output Transfer Curve for details


Output Transfer Curve File

The output transfer curve defines the relationship between the calculated output and the actual output. It is only applicable in Run mode but applys to both DC and RF outputs. Use this to linearize a nonlinear element such as a RF or optical modulator. For example, if a modulator has a low response at low levels then the transfer curve can be used to bump up the output at those low levels. A linear output transfer curve gives a 1:1 calculated to output relationship: e.g. double the calculated output level gives double the actual output level. A nonlinear curve must be defined by a  text file. The file rules are:
Following is the contents of a short sample file which has several discontinuities defined. Note that although "0 0;" is defined, it is implied and not necessary. The last line overrides the default "1023 65535;".
0    0;
512  32768;
750  50000;
1023 65000;