Ophir Optronics Ltd QSR Manuel D’Utilisation
Chapter 4 – Measuring with the Thermopile Head
Optimizing the Readings
Optimizing the Readings
StarLab can be optimized to achieve the most accurate and efficient results. This
section describes the most commonly used optimizations: offset, zeroing the
instrument, and setting line frequency.
section describes the most commonly used optimizations: offset, zeroing the
instrument, and setting line frequency.
Applying an Offset
When there is thermal background in the environment, thermopile heads may
show a non-zero power reading, even when there is no laser. For example, the
display reads 0.1 Watts when the laser is blocked, and 20.5 Watts when laser
power is applied. In this case, the true power is 20.5 - 0.1 = 20.4 Watts. To
subtract the background, apply an offset while the laser is blocked. The display
will now read zero, and the 0.1 Watt background will be subtracted from all
subsequent readings. The laser power reading will be 20.4 Watts.
show a non-zero power reading, even when there is no laser. For example, the
display reads 0.1 Watts when the laser is blocked, and 20.5 Watts when laser
power is applied. In this case, the true power is 20.5 - 0.1 = 20.4 Watts. To
subtract the background, apply an offset while the laser is blocked. The display
will now read zero, and the 0.1 Watt background will be subtracted from all
subsequent readings. The laser power reading will be 20.4 Watts.
To apply an Offset:
1. Click
in the Graph Configuration Area. The Offset button
toggles to Offset On when the Offset is activated. The Offset value is
displayed under the main measurement reading in the Numeric Display
Area.
displayed under the main measurement reading in the Numeric Display
Area.
To cancel the Offset:
1. Click
in the Graph Configuration Area. The Offset value is
cancelled.
Note: If you suspect that the instrument has a permanent zero offset,
disconnect the head while the head is in power measurement mode. If
StarLab still shows a similar reading even when the head is not
connected, zero the instrument. For information on zeroing the
instrument, refer to Zeroing the Instrument on page 4-37.
StarLab still shows a similar reading even when the head is not
connected, zero the instrument. For information on zeroing the
instrument, refer to Zeroing the Instrument on page 4-37.
Zeroing the Instrument
In the USBI, Pulsar and Quasar, all adjustments, including zeroing internal
circuits, are performed from the software. This ensures simple and accurate
realignment. For best performance, it is recommended to zero the instrument
frequently.
circuits, are performed from the software. This ensures simple and accurate
realignment. For best performance, it is recommended to zero the instrument
frequently.
For the USBI instrument:
With thermopile heads, it is necessary to zero the instrument with no head
attached, and then repeat with the head attached.
With photodiode heads it is only necessary to zero with the head attached.
With thermopile heads, it is necessary to zero the instrument with no head
attached, and then repeat with the head attached.
With photodiode heads it is only necessary to zero with the head attached.
For the Pulsar and Quasar instruments:
With all heads, it is only necessary to zero the instrument with the head attached.
With all heads, it is only necessary to zero the instrument with the head attached.
To zero the USBI instrument with NO head attached:
1. Start up the instrument with no head attached: unplug the USB cable,
disconnect the head, and replace the USB cable.
StarLab User Guide
37