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BSA Flow Software Installation and User's Guide - CSI

BSA Flow Software Installation and User's Guide - CSI

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Sensitivity It sets the high voltage to the photo-multiplier. The recommended starting<br />

level is around 1000 V. Depending on the seeding, the laser power, the LDA<br />

optics <strong>and</strong> the position of the measurement volume in the flow, the optimum<br />

may be higher or lower.<br />

Optimisation should take both this property <strong>and</strong> the Signal gain into account.<br />

The criterion may be the validation rate or the data rate or some compromise<br />

between them, depending on the application. The validation rate <strong>and</strong> data<br />

rate are displayed in the System monitor window.<br />

Signal gain: It sets the gain of the photo-multiplier signal amplifier. Recommended<br />

starting level is around 20 dB. Should be optimised together with the high<br />

voltage as described above.<br />

Burst detector<br />

SNR level It sets the SNR threshold level of the SNR based burst detector. The default<br />

value is 0 dB. High values will reject more noisy bursts, leading to higher<br />

validation <strong>and</strong> lower data rate, <strong>and</strong> vice versa.<br />

Anode current limit To protect the photo-multiplier tube e.g. when approaching walls, the <strong>BSA</strong><br />

includes a current limiter circuit which reduces the high voltage if the photomultiplier<br />

anode current exceeds the set limit. For Dantec st<strong>and</strong>ard photomultipliers<br />

57X08 <strong>and</strong> those used in <strong>Flow</strong>Lite optical systems, the limit<br />

should be set to 1500 µA. For other photo-multipliers, please consult the<br />

suppliers’ technical specifications.<br />

Level validation ratio Level validation looks at the ratio between the two highest peaks in the burst<br />

spectrum. If the ratio is higher than the specified value, the burst is validated,<br />

otherwise it is rejected.<br />

PDA 1, 2 properties: Range <strong>and</strong> gain<br />

High voltage level: sets the high voltage to the photo-multiplier. The<br />

recommended starting level is around 1000 V. Depending on the size of the<br />

particles, the laser power, the PDA optics <strong>and</strong> the position of the<br />

measurement volume in the flow, the optimum may be higher or lower. For<br />

optimum particle size measurements, you must have balanced signals, <strong>and</strong> an<br />

optimum combination of high voltage <strong>and</strong> signal gain. For balancing, adjust<br />

the high voltage of PDA2 <strong>and</strong> PDA3 till you get the same amplitude as<br />

LDA1. When this is obtained, set the Balance high voltage to Yes. You can<br />

now adjust the high voltage of all three channels using the LDA1 channel<br />

only. The gain of PDA2 <strong>and</strong> PDA3 is automatically set to the same level as<br />

LDA1.<br />

Optimisation should take both the Sensitivity<strong>and</strong> the Signal gain into<br />

account. The criterion may be the validation rate or the data rate or some<br />

compromise between them, depending on the application. The validation rate<br />

<strong>and</strong> data rate are displayed in the System monitor window.<br />

5-20 <strong>BSA</strong> <strong>Flow</strong> <strong>Software</strong>: Project explorer objects

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