10
preferred. Data acquisition systems reduce labor, potential
exposure, and collect more accurate data than manual read-
ings alone. The following section discusses the data acquisi-
tion systems currently in use by NIOSH.
DATA ACQUISITION
Data collection represents the final phase of a field moni-
toring site. Following the installation of the required
instrumentation, the routing of the data cables takes place,
eventually converging at a central outby location. At this
location, the data acquisition system resides and continu-
ously monitors the site until the study ends or mining
operations make access no longer possible. At this point,
the entirety of the field instrumentation will be sacrificed,
leaving only the data acquisition system to be recovered.
The data can then be processed and analyzed to further
understand ground movement and interaction. Currently,
NIOSH uses two data acquisition systems, the Miniature
Data Acquisition System (MIDAS) and the Campbell
Scientific 21XQM Micrologger (Jones, 2012 Campbell
Scientific, Inc., 1995).
The MIDAS system is a composite of various equip-
ment elements that together form a high-accuracy analog-
to-digital data recording system. This system is compatible
with a wide range of resistive instruments. With its intrin-
sic safety and MSHA permissibility, the datalogger is espe-
cially suited for usage in the return-air courses of coal mines
(see Figure 17). It can monitor up to 8 individual chan-
nels simultaneously or a combination of 4 individual and
4 differential channels when paired with the M4IAGPAR5
four-channel instrumentation amplifier board.
Data extraction is streamlined and user-friendly, facili-
tated by wireless transfers when near the MIDAS Reader
interface, where the data is saved onto a micro-SD card. In
many field locations, several MIDAS devices are employed
to meet the demands of the instrumentation plan. With its
extended battery life (up to one year), the MIDAS datalog-
ger is a preferred choice for prolonged surveillance locations.
While there are restrictions on cable lengths, 200 ft. from
the monitoring location is typically adequate for most sites.
Details on constraints, circuit diagrams, software instruc-
tions, and signal amplification computations are available
in the instruction manual (Golder Associates, 2013).
The Campbell datalogger is a single unit with an inte-
grated power supply, keyboard, and display and is also
MSHA-approved for monitoring in the return airway
of coal mines (see Figure 18). It offers 8 differential and
16 single-ended channels, 4 excitation outputs, 2 analog
outputs, 6 control ports, and 4 pulse counters. With an
added multiplexer, it supports up to 16 differential and 32
single-ended readings. The 21XQM micrologger can con-
duct 36 measurements using three-wire strain gauges for
Hollow Inclusion Cells and supports cables up to 1,000 ft.
Data is stored in the SM716QM module and accessed via
Campbell Scientific’s PC interface (Campbell Scientific,
Inc., 1995).
LIMITATIONS
This paper has provided a comprehensive overview of
ground-control monitoring by NIOSH researchers using
Figure 17. MIDAS showing internal components (top) and
wired with weather pack connectors (bottom)
preferred. Data acquisition systems reduce labor, potential
exposure, and collect more accurate data than manual read-
ings alone. The following section discusses the data acquisi-
tion systems currently in use by NIOSH.
DATA ACQUISITION
Data collection represents the final phase of a field moni-
toring site. Following the installation of the required
instrumentation, the routing of the data cables takes place,
eventually converging at a central outby location. At this
location, the data acquisition system resides and continu-
ously monitors the site until the study ends or mining
operations make access no longer possible. At this point,
the entirety of the field instrumentation will be sacrificed,
leaving only the data acquisition system to be recovered.
The data can then be processed and analyzed to further
understand ground movement and interaction. Currently,
NIOSH uses two data acquisition systems, the Miniature
Data Acquisition System (MIDAS) and the Campbell
Scientific 21XQM Micrologger (Jones, 2012 Campbell
Scientific, Inc., 1995).
The MIDAS system is a composite of various equip-
ment elements that together form a high-accuracy analog-
to-digital data recording system. This system is compatible
with a wide range of resistive instruments. With its intrin-
sic safety and MSHA permissibility, the datalogger is espe-
cially suited for usage in the return-air courses of coal mines
(see Figure 17). It can monitor up to 8 individual chan-
nels simultaneously or a combination of 4 individual and
4 differential channels when paired with the M4IAGPAR5
four-channel instrumentation amplifier board.
Data extraction is streamlined and user-friendly, facili-
tated by wireless transfers when near the MIDAS Reader
interface, where the data is saved onto a micro-SD card. In
many field locations, several MIDAS devices are employed
to meet the demands of the instrumentation plan. With its
extended battery life (up to one year), the MIDAS datalog-
ger is a preferred choice for prolonged surveillance locations.
While there are restrictions on cable lengths, 200 ft. from
the monitoring location is typically adequate for most sites.
Details on constraints, circuit diagrams, software instruc-
tions, and signal amplification computations are available
in the instruction manual (Golder Associates, 2013).
The Campbell datalogger is a single unit with an inte-
grated power supply, keyboard, and display and is also
MSHA-approved for monitoring in the return airway
of coal mines (see Figure 18). It offers 8 differential and
16 single-ended channels, 4 excitation outputs, 2 analog
outputs, 6 control ports, and 4 pulse counters. With an
added multiplexer, it supports up to 16 differential and 32
single-ended readings. The 21XQM micrologger can con-
duct 36 measurements using three-wire strain gauges for
Hollow Inclusion Cells and supports cables up to 1,000 ft.
Data is stored in the SM716QM module and accessed via
Campbell Scientific’s PC interface (Campbell Scientific,
Inc., 1995).
LIMITATIONS
This paper has provided a comprehensive overview of
ground-control monitoring by NIOSH researchers using
Figure 17. MIDAS showing internal components (top) and
wired with weather pack connectors (bottom)