Ophir Optronics Ltd QSR Manuale Utente

Chapter 4 – Measuring with the Thermopile Head

Configuring Measurement Settings in Energy Mode

To configure the energy threshold:

1. Select the energy threshold setting from the following options on the

Threshold drop down list in the Measurement Parameters Area:

LOW – Use this setting if you are measuring small energies and the
unit does not trigger.

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MED – This is the default factory setting.

HIGH – Use this setting if the unit triggers when there is noise.

OPTICAL – Use this setting to enable the optical trigger for heads
with this capability.

Figure 4-5 Energy Threshold Drop Down List

Note 3A-P Head Users: The older model of the 3A-P head has special

circuitry enabling it to trigger on energy pulses of very low energy. A
special photodiode trigger alerts the instrument to start integration
when a pulse is received. The photodiode trigger enables the 3A-P
head to react to smaller pulses than are measured by other heads that
trigger on the rising thermal signal. Newer models of the 3A-P do not
need the optical trigger to achieve low energy measurement and do not
have this feature.

Selecting OPTICAL from the Threshold drop down list enables the
optical trigger. In some cases, however, the optical trigger will not
work, and one of the thermal trigger settings - LOW, MED, or HIGH
should be selected. Thermal triggering on 3A-P heads is applied when:

The wavelength is outside the range of the photodiode, i.e. outside of
0.19 - 1.064µm.

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You are measuring the energy of a shuttered pulse of a continuous
laser. In this case, the peak power is too low to trigger the photodiode.

The instrument fails to trigger on the OPTICAL setting.

When using the optical trigger, the instrument should be able to
measure down to 0.1 - 0.2 mJ, depending on the wavelength. When
using the thermal trigger (LOW, MED, or HIGH), do not attempt to
measure less than about 1mJ.

StarLab User Guide