Stanford Research Systems LDC500, Руководство по эксплуатации и обслуживанию

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2 – 18 Getting Started
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2.3.7 Optical power calibration
To successfully operate the LDC500 in optical power units (mW),
a valid responsivity value is needed. If you already know the re-
sponsivity of your photodiode (by previous measurement or from
the datasheet), you can directly enter the value by pressing the LD
[Config] button, and navigating to the “LD Cfg: PD resp” item.
Alternatively, you can use the LDC500 to measure and set the pho-
todiode responsivity. To do this, you will need to be able to operate
your laser diode, and have access to a laser power meter to measure
the actual optical power being generated by the laser.
For best results when calibrating responsivity, the LD driver should
be operated in CP mode, with “PD units: use mW:” set to “N” (raw
μ
A photodiode units). Alternatively, the LD driver can be operated
in CC mode, but the photodiode readings may drift slightly during
calibration.
•
Make sure the LD driver is ON, preferably in CP mode (with
“PD units: use mW:” set to “N”), or else in CC mode.
•
Adjust the LD output so that a good, stable optical power read-
ing can be obtained with the laser power meter.
•
Press [Config], and navigate to the “LD Cfg: PD calib at:” item.
•
Note the (stable) optical power reading, in mW, and enter the
value using the keypad or wheel.
•
Pressing [Enter] will cause the LDC500 to take the most recent
(internal) reading of photodiode current, and divide it by the
power calibration just entered, to calculate a new value for the
PD responsivity.
•
If the calibration is successful, the LDC500 will play a short
4-note tune. The new value of responsivity can be checked by
pressing [ ] to select “LD Cfg: PD resp”.
Note that active responsivity calibration (using the “LD Cfg: PD calib
at:” item) is prohibited when the LD driver is o
ff
, or when operating
in CP mode with mW units.
2.3.8 Configuring LD trip-offs
Under certain limit conditions, it is important to shut down the LD
driver output. To customize which events will lead to shutdown,
LDC500 Series Laser Diode Controllers