Screen page "Bode Plot" 

This function is reserved for engineers and technicians who are experienced in control technology. We can offer you appropriate training on request. 

With the aid of the Bode plot you can analyze and optimize the speed control loop, taking into account the mechanical characteristics of the machine. 

The Bode plot draws the frequency response of the speed control loop. The system is stimulated by a sinusoidal input variable. The output variable has the same frequency, but a different amplitude and some degree of phase shift. 

The relationship between the amplitude as a function of frequency (amplitude response) and the phase shift as a function of frequency (phase response) provides a complete description of the dynamic characteristics of the control loop. 

Amplitude response 

The amplitude response is the frequency-dependent amplitude characteristic (gain), shown on a logarithmic scale. 

Phase response 

The phase response is the frequency-dependent phase-shift characteristic. 

The following characteristic data are used for a qualitative description of the open loop frequency response: 

Phase reserve (open loop) 

The spacing between the phase characteristic curve and the -180° phase-shift line at the cut-off frequency, i.e. the frequency at which the amplitude characteristic (gain) has fallen to 0 dB. 

Amplitude reserve (open loop) 

The spacing between the amplitude characteristic (gain) and the 0 dB level at a phase shift of -180°. 

The characteristics of the closed control loop are evaluated with the aid of the Bode plot, using the expressions "bandwidth" and "peaking": 

Bandwidth (closed loop) 

Bandwidth is the range of frequencies limited by the frequencies where the logarithmic amplitude characteristic (gain) falls off by  -3 dB. 

Peaking (closed loop) 

The expression "peaking" describes an overshoot of the closed control loop, corresponding to the maximum in the  amplitude response.
 

Bode plot 

Starts recording the data. 

Stop 

Stops recording data.
 

Save 

Saves the measurements that were recorded to a data medium in CSV format (can be evaluated by MS-Excel).
 

Load 

Loads a CSV file and displays the curves in a diagram.
 

Update 

Loads and display the latest set of recorded data.
 

Cursor function 

When a set of data is displayed (from a file, or by starting a recording), a mouse click in the coordinate system displays the measured values for the signals at the selected time. A click outside the coordinate system sets the display values back to 0.
 

Parameter ... 

Call up the screen page "Bode Plot Parameter"
This page is used to define the frequency range and the number of steps.