Q: What is the maximum number of 844-PE-USB I can connect to a control PC?
A: There is no specific upper limit. However, the user is advised to test themselves and do not connect too many power meters so that the meter and/or the PMManager performances are not deteriorated.

Q: I have 844-PE-USB's predecessor USB virtual power meters. Can I use the 844-PE-USB firmware to upgrade them?

A: The only legacy model you can use this firmware to upgrade is 841-PE-USB. It is not compatible with 841-P-USB or 842-PE-USB.    

Q: I have an 841-P-USB or 842-PE-USB. Can I use a 844-PE-USB as a replacement?
A: If you are using photodiode detectors (818-xx/DB, 918D, 819C, and 819D series), then you can use the 841-PE-USB as a replacement. However, the 844-PE-USB is not compatible with either of the 818P or 818E series detectors. The application program and computer commands are different as well.

Q: Can I use a Newport Power Meter Application to communicate with the 844-PE-USB? 
A: No. The Newport Power Meter Application is only compatible with the 1830-R series and the 1936-R/2936-R power meters. Also note that the command lists are different between the 844-PE-USB and the meters compatible with the Newport Power Meter Application.

Q: The 844-PE-USB power meter has 'Power Density (W/cm2)' measurements available. Can I use the sensor with the active area for power density or irradiance measurements?
A: Our standard detectors can be used for power density measurements for relatively well defined beams. However, it is not recommended to use the full sensor active area in the measurements, because the responsivity changes at the edge of the photodiode. Instead, place a small aperture of a known size to make sure that all the beam falls well within the sensor, and enter the aperture size in the power meter. For the irradiance measurement of a diverging or Lambertian light source, we recommend 818-RAD (P/N 7N6080A) with its compatible power meter.