Electronically Calibrated – PowerMonitor

PowerMonitor

The ElectronicCalibrated-PowerMonitor (EC-PowerMonitor) for beam power measurement conforms the highest industrial standards:

  • State-of-Art power meter with applicability as a reference
    system
  • Long term stability by robust configuration and use of a contactless flowrate sensor
  • Accuracy and reproducibility by use  of high-grade sensors and components
  • Authentic operation in rough operation environment by robust and  rugged  configuration
  • Redundancy of the measuring results  by integrated selftest-function 

Application

One of the most important parameters of laser material processing is the beam power within the process zone.

Due to absorption processes in the beam guidance and the focussing optics, the beam power is reduced.

Practical experience has shown that dirt and deterioration of optical components cause a growing power dissipation within the beam path from time to time. Furthermore, the machining result can be affected negatively.

Due to  the power measurement  in the process zone the user gets information about the beam power at the workpiece. To avoid a reduction of the machining quality, the observation of power dissipation should be done over a longer period of time as well as a punctual accomplishment of maintenance. This can be done by a regular repetition of the power measurement.

The EC-PowerMonitor not only measures the beam power in the process zone, but also possesses an integrated selftest-function.

Thus, the functional capability and the accuracy of the measuring device can be checked any time.

Technical description

The method is to direct the laser beam with a parabolic mirror into a cylindrical absorber. There is an absorbing coating on its inner surface. Thus, the laser power will be absorbed more uniformly on the surface and any radiation leakage is avoided. This system can be used for highest laser powers and power densities.

With a high-precision measurement of the temperature difference and flowrate of the coolant, the power of the absorbed laser beam can be determined exactly.

All parts in the device which get in contact with the cooling water are made of copper or brass to avoid any corrosion in the coolant circuit (due to different chemical potentials).

A pneumatic shutter is used to close the beam input aperture and to protect the entrance mirror of the EC-PowerMonitor against dust. 
An electronic calibration was integrated for self-testing. 
Instead of the laser, a heating element can be used to heat the coolant. This way, two independent systems can be compared for self-test purposes:

1.  The calorimeter that measures the heat flow through the absorber.

2. The amount of electric energy that passed through the heating element.
This redundancy of two independent measuring systems ensures maximum reliability.

 

Technical data

 Power range:  200 W bis 10 kW
 Max. power density:  12 kW/cm²
 Reproducibility:  ± 1 %
 Absolute accuracy:  ± 2 %
 Time constant:  15 sec. 99 % of the final value
 Flow-rate:  min. 5 liters per minute
 Free aperture:  48 mm
 Dimensions (Height x Length x Depth):   205 mm x 242 mm x 400 mm
 Power supply:  24V RS485 only for power measurement
   240 V for selftest-function
 Weight  16 kg

The EC-PowerMonitor is able to show the measured values in different ways:

  • The integrated display shows beam  power, flow-rate and coolant temperature.
  • The values can be displayed and  analysed with the help of the software PMS. The self-testing function enables checking of the functional capacity  and the accuracy of the EC-PowerMonitor. The communication to  the computer can be done via USB or RS485-PRIMES-Bus.
  • In conjunction with a FocusMonitor, it  is possible to transfer the measured values directly into the software LDS.  Furthermore, the values will be used  for absolute power density calculations.
  • An analogue output enables to diplay and to protocol the measured values.

Options

The following options are available:

  • SPS interface for connecting to a system control or laser system
  • Fiber adapter for the direct connection  of a beam guiding fiber
  • A mount for the FocusMonitor