Power Wizard PW-250 Operating
Instructions
(cont.)
• The PW-250 can be used to measure laser power anywhere along the beam path, including between a focusing lens and
work piece, and can be used to measure power emitted from optical fibers.
Important Note: While the PW-250 target has a very high damage threshold, the target should never be placed
at the focal point of a lens. Place the PW-250 target either in front/above or behind/below the
beam’s focal point, thus minimizing power density without overfilling the target area. The maxi-
mum allowable power density at the target is 20 kW/cm2; exposure to power densities above this
value may damage the target, leading to loss of accuracy and calibrated performance.
• Erroneous readings may indicate one or more of the following conditions exists: a) the PW-250 was not reset for at least
two seconds, b) the target is not being held stationary in the beam path, c) the beam is not completely within the target
area, d) laser power is fluctuating too rapidly, or e) the PW-250 is malfunctioning.
Calibration
Each PW-250 is individually calibrated to ±5% accuracy at the 10.6 micron (µm) CO2wavelength with calibration trace-
able to the National Institute of Standards and Technology (NIST).
Maintenance
PW-250 battery life is approximately five years, even with constant use, for a capacity of about 25,000 measurement cycles.
Current drain of the unit is less than 0.5 mA. Replace batteries when “BAT” appears on the LCD display. To access the
three CR2025 lithium batteries, remove the three screws on the rear half of the PW-250 case and lift the rear cover away.
DO NOT remove the screws on the front (display) side.
Warranty
The PW-250 is warranted for twelve (12) months from the date of purchase, provided it is used per the operating instruc-
tions described above. SYNRAD, Inc. is not responsible for damage caused by improper use, particularly water immersion or
overheating. SYNRAD, Inc. will repair or replace at no charge any PW-250 that fails due to manufacturing or design defect.
Defective unit must be returned to SYNRAD, Inc. freight prepaid. Prior to returning the unit, you must first obtain a Return
Authorization (RA) number by calling SYNRAD Customer Service at 1.800.796.7231, outside the U.S. at 1.425.349.3500
or fax to 1.425.349.3667.
Theory of operation
The PW-250 uses a patented measurement principle to achieve unprecedented convenience and performance. The unit
measures the rate of change of temperature (both heating and cooling) induced in an aluminum mass by incident laser
power. A sophisticated analog computer evaluates the temperature of the probe, the cooling rate before laser application,
and the heating rate of the probe during laser application. Knowledge of these three values is sufficient to compute incident
power using mathematical formulas, regardless of the target’s immediate thermal history.
Upon activating and initializing the computer (by pressing and holding the RESET/POWER button for two seconds), the
present cooling rate of the laser target is stored into memory. If the target was not previously exposed, the current cooling
rate is zero. Releasing the RESET/POWER button starts a timer that produces an audible beeping signal after approximately
six seconds. During the six-second measurement window, the target is exposed to laser power and the heating rate is then
calculated. The calculated power value, based on the stored cooling rate and present heating rate, is continuously updated
on the LCD display. When the heating rate settles and stabilizes about three seconds after exposure, the correct power
reading is displayed. The thermal settling rate is sufficiently shorter than the six-second timing sequence, to allow adequate
time to place the target into the beam and allow stabilized conditions to be reached. After the timing sequence has elapsed
(indicated by a series of beeps), the power reading remains locked on the LCD display for a period of 12–15 seconds so the
PW-250 can be removed from the laser beam and the reading can be recorded. After 12–15 seconds, a series of fast beeps
indicates the PW-250 is automatically shutting down.
