Controlling a PWM transducer using Xenta 102-AX PWM_1 output

Issue

The Xenta 102-AX PWM_1 (one output PWM) setting is a true duty cycle output.  How can you control a PWM transducer?

Product Line

TAC Vista

Environment

Xenta 102-AX, Universal Output 2

PWM Transducer

Cause

The problem is that 0% on a duty cycle output is no pulse at all and 100% is continually on. All electronic transducers must have some pulse to control it to 0%, often 0.1 seconds. Many of them will not accept a continually on signal as 100%.

Values for two of the most industry common PWM transducers are detailed below.  Calculations provided can be used to calculate any required duty cycle limits.

Resolution

This example assumes a PWM transducer that requires a pulse width modulated signal between 0.1 and 5.2 seconds.

  1. Set the stroke time to a value slightly larger than the required maximum pulse.
    UnivOut2_Object.SCPTdriveTime = 5.3 seconds
  2. Set the minimum range to a percentage of the drive time that will result in a 0.1 second pulsed output.
    UnivOut2_Object.nviUnvOutput2.SCPTminRnge = 1.885%
    0.01885 * 5.3 = 0.099905 seconds
  3. Set the maximum range to a percentage of the drive time that will result in a 5.2 second pulsed output.
    UnivOut2_Object.nviUnvOutput2.SCPTmaxRnge = 98%
    0.98 * 5.3 = 5.194 seconds
  4. Set the minimum pulse to 0.1 second.
  5. A 0-100% signal on Universal Output 2 will now modulate the pulse width between 0.1 and 5.2 seconds.

This example assumes a PWM transducer that requires a pulse width modulated signal between 0.1 and 25.6 seconds.

  1. Set the stroke time to a value slightly larger than the required maximum pulse.
    UnivOut2_Object.SCPTdriveTime = 25.7 seconds
  2. Set the minimum range to a percentage of the drive time that will result in a 0.1 second pulsed output.
    UnivOut2_Object.nviUnvOutput2.SCPTminRnge = 0.39%
    0.0039 * 25.7 = 0.10023 seconds
  3. Set the maximum range to a percentage of the drive time that will result in a 25.6 second pulsed output.
    UnivOut2_Object.nviUnvOutput2.SCPTmaxRnge = 99.61%
    0.9961 * 25.7 = 25.59977seconds
  4. A 0-100% signal on Universal Output 2 will now modulate the pulse width between 0.1 and 25.6 seconds.