Wet Labs ECO VSF, User Manual

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ECO VSF User’s Guide (VSF) Revision AN 14 Sept. 2011 17
6. Testing and Calibration
Prior to shipment, each ECO is characterized to ensure that it meets the instrument’s
specifications.
6.1 Testing
When the instrument is completely assembled, it goes through the tests below to ensure
performance.
6.1.1 Dark Counts
The meter’s baseline reading in the absence of source light is the dark count value. This is
determined by measuring the signal output of the meter in clean, de-ionized water with
black tape over the detector.
6.1.2 Pressure
To ensure the integrity of the housing and seals, ECO s are subjected to a wet hyperbaric
test before final testing. The testing chamber applies a water pressure of at least 50 PSI.
6.1.3 Mechanical Stability
Before final testing, the ECO meters are subjected to a mechanical stability test. This
involves subjecting the unit to mild vibration and shock. Instrument functionality is
verified afterwards.
6.1.4 Electronic Stability
This value is computed by collecting a sample once every 5 seconds for twelve hours or
more. After the data is collected, the standard deviation of this set is calculated and
divided by the number of hours the test ran. The stability value must be less than 3 counts.
6.1.5 Noise
The noise value is computed from a standard deviation over 60 samples. These samples
are collected at one-second intervals for one minute. A standard deviation is then
performed on the 60 samples, and the result is the published noise on the calibration form.
The calculated noise must be below 3 counts.
6.1.6 Voltage and Current Range Verification
To verify that the ECO operates over the entire specified voltage range (7–15 V), a
voltage-sweep test is performed. ECO is operated over the entire voltage range, and the
current and operation is observed. The total power consumption (voltage times current)
must remain below 600 mW over the entire voltage range.
6.2 Calibration
Calibration of the ECO VSF involves the following steps.
1. Numerical determination of the volume weighted angular region for each scattering angle.