User's Manual

MicroStrain, Inc.
Operation
Let’s discuss the operation of the SG-Link® OEM and base station in conjunction with
the Agile-Link™ host software.
The SG-Link® OEM has a differential input channel (strain channel), a single ended
input channel (analog channel) and an on-board temperature sensor channel. The SG-
Link® OEM samples these three channels using four different selectable methods. The
data is either stored temporarily on-board the SG-Link® OEM or immediately
transmitted to a base station, depending on the sampling method. The base station is read
by the host software as data is received, and the host software displays and/or saves the
data to file.
The differential input is assigned to channel 1, the single ended input is assigned to
channel 4, and the on-board temperature sensor is assigned to channel 3. Channel 2 is
also in place and reserved for future use; it has no use currently and should be kept
inactive. The differential channel with its connected sensor is excited with 3 volts and
the resultant is first passed through a 2-stage amplification (being a fixed instrumentation
amplifier and a user programmable gain amplifier with programmable offset, on through
an anti-aliasing filter (3dB down @ 500 Hz; low pass filters with cutoff @ 500 Hz), and
into the 12 bit A-to-D converter. The single ended input with its connected sensor and
the temperature sensor are excited with 3 volts and feed directly into the 12 bit A-to-D
converter. The 12 bit A-to-D converter sends the 3 channels to the microprocessor. The
firmware in the microprocessor processes the digital sampling into raw data and,
depending on the sampling method selected, either writes the data as it is captured to the
flash memory or sends the data through the serial communication interface to the radio
transceiver. The transceiver in turn transmits the data to any listening base station.
Please refer to the Electrical Block Diagram section of this manual for a visual
representation of the SG-Link® OEM, base station and host software operation. Please
refer to the Differential Input Channel and Single Ended Input Channel sections of this
manual for an in-depth discussion of their use and operation.
In the DATALOGGING sampling method, the SG-Link® OEM may be configured to
sample data as fast as 2048 samples per channel per second to as slow as 32 samples per
channel per second. Datalogging can be finite or continuous. In finite datalogging, a
sampling duration is set and the datalogging session will last the duration once initiated.
The data will be written to the memory on-board the SG-Link® OEM during the session.
In continuous datalogging, the one session will last until the memory is full. Multiple
finite datalogging sessions may be conducted with the SG-Link® OEM before its
memory is full. No data is transmitted over the air to the base station during datalogging.
When datalogging is completed (one or more sessions), the software provides for the data
to be downloaded from the SG-Link® OEM through the base station. The software
parses the data into CSV formatted files for further analysis.
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