Particle Measuring Systems LASAIR II 550L Operator's Manual

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Channel Particle Scale ConsiderationsChannel Particle Scale Considerations
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J-7J-7
The counts recorded at a given scale are a function of the accuracy andThe counts recorded at a given scale are a function of the accuracy and
resolution of the instrument reading the channel, as weresolution of the instrument reading the channel, as well as the accuracy andll as the accuracy and
resolution of the LASAIR II output. The LASAIR II resolution is about 0resolution of the LASAIR II output. The LASAIR II resolution is about 0.025.025
mA, and the accuracy mA, and the accuracy is better than 1% of full scale. If the recording is better than 1% of full scale. If the recording device isdevice is
perfect, and only LASAIR II errors are seen, then the performance will be asperfect, and only LASAIR II errors are seen, then the performance will be as
follows:follows:
•• If a channel is set to 1000 If a channel is set to 1000 for the scale, then the readings will be for the scale, then the readings will be within 10within 10
counts (i.e. 1%).counts (i.e. 1%).
•• The minimum detectable change is about 2 counts (i.e., 1000/(16 mA/The minimum detectable change is about 2 counts (i.e., 1000/(16 mA/
0.0250.025 mA) or 1.mA) or 1.56).56).
In summaryIn summary, setting the scale factor is a b, setting the scale factor is a balance between setting the scale largealance between setting the scale large
enough to cover the worst case expected count output, while at the same timeenough to cover the worst case expected count output, while at the same time
setting it small enough to accurately show normal evsetting it small enough to accurately show normal events.ents.
Example:Example:
The user would like to differentiate between 99, 100, and 101 counts.The user would like to differentiate between 99, 100, and 101 counts.
Then:Then:
11 Range = 16 mA = 20-4Range = 16 mA = 20-4
22
With min. detectable change of 0.025 mA, this means the range can be dividedWith min. detectable change of 0.025 mA, this means the range can be divided
into a max of 640 channels = 16 mA/0.025 mA.into a max of 640 channels = 16 mA/0.025 mA.
33
Then by setting 4 mA = 0 counts and 20 mA = 640 countsThen by setting 4 mA = 0 counts and 20 mA = 640 counts
44 We derive:We derive:
99 Counts = 6.475 mA99 Counts = 6.475 mA
100 Counts = 6.500 mA100 Counts = 6.500 mA
101 Counts = 6.525 mA101 Counts = 6.525 mA

Particle Measuring Systems LASAIR II 550L Specifications

General

Brand	Particle Measuring Systems
Model	LASAIR II 550L
Category	Measuring Instruments
Language	English