ESCON: Analog IO properties

Topic:

• What functionalities are available with the analog IOs?
• How to configure the analog IOs?
• Pro’s and Con’s of using the analog IOs?

Situation:

The ESCON has 2 analog inputs and 2 analog outputs, aside from the external physical analog IOs some ESCON controllers have onboard potentiometers that can be used as part of the analog functionalities.

The voltage range for the analog inputs is +/- 10VDC.
The analog outputs have an output voltage range of +/- 4VDC.

ESCON's analog inputs:

In the case of inputs, the available functionality is best used when variable control is desired. For this you can set the analog input as the set value command input, for example speed as shown below.

Or you can configure a variable max current limit instead of the typical fixed current limit (maxon rule of thumb is 2x or 3x nominal current of motor):

Additionally, if your system requires different ramp rates, you can configure an analog input for this purpose:

When configuring the analog inputs or outputs its always going to be a linear relationship with the input/output voltage and the function you want to command.

• Example 1:
  Based on the first screenshot there is the following configuration present: 
  0rpm at 0V and 10000rpm at 10V
  => This results in a scaling factor of 1000rpm per 1V.
  • If there is just an unipolar set value present (i.e. only 0 ... 10V), the direction of rotation has to be commanded by a digital input.
  • If a bidirectional set value (i.e. +/-10V) is applied to the analog input, any negative voltage means commanding the negative direction of rotation, i.e. applying -10V results in -10000rpm and -5V means -5000rpm. This is exactly the same behavior like present in case of the following set value configuration:
    -10000rpm at -10V and 10000rpm at 10V 
    
    
• Example 2:
  If you have not configured a digital input for direction, you can configure the analog input to be as follows:
  -10000rpm = 0V and 10000rpm = 10V
  => 5V would be your 0rpm and the scaling would now be 2000rpm per 1V.

Please find the technical specification and internal design of the analog inputs of your concrete's ESCON product type by its "Hardware Reference". In case of an "ESCON 50/5" (P/N: 409510) the specification looks like this:

ESCON's analog outputs:

Regarding the analog outputs, you can see below the available functionalities where most are used as some sort of monitoring output. The most common one used is the “Actual current averaged” when the drive is set to Speed control closed loop.

Please find the technical specification and internal design of the analog outputs of your concrete's ESCON product type by its "Hardware Reference". In case of an "ESCON 50/5" (P/N: 409510) the specification looks like this:

Some general remark:

The analog inputs are useful for variable, dynamic set point commanding of the ESCON by means of an external voltage signal. However, it must be taken into account that the analog inputs/outputs and internal signal processing use a 12 bit A/D converter. This results in some principal system-related limitations and tolerances in signal processing:

• A 12 bit A/D converter offers a resolution of 4096 (= 2^12) over the specified voltage range (i.e. +/-10V = 20V => approx. 5 mV for analog inputs and +/-4V = 8V => approx. 2 mV for analog outputs).
• It has to be considered that analog signals are sensitive to signal interferences, e.g. by unshielded motor cables.
• A general noise and oscillating signal processing of 1 bit must also often be expected.

The commanded set point is therefore subject to a some tolerance depending on the configured speed resp. current range. If a speed range of +/-10000rpm is covered by the specified analog input voltage range +/-10V and its 12 bit A/D converter, this means a set value resolution of 5 rpm (= 20000rpm / 4096). Taking into account a noise or offset part of the A/D conversion, a tolerance of +/-5 rpm must be typically assumed for the set point commanding in this case. 

Cross Reference:

• ESCON: Using an external potentiometer for set value commanding