MREL DATA TRAP II, Operation Manual

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center conductor and the shielding connections do not touch each other. It
is a good idea to check the total resistance of the
PROBECABLE and coaxial
cable circuit at the BNC connector using a blaster’s galvanometer to ensure
that there are no bad connections.
10. At the DataTrap II™ Data/VOD Recorder end, connect the coaxial cables to
the input connectors (labeled 1 2 3 4 5 6 7 8 ) located on the outside and at
the back of the DataTrap II™ Data/VOD Recorder .
11. The PROBECABLE installation aspects of the test are complete. The
DataTrap II™ Data/VOD Recorder is now ready to be prepared to record the
test.
5.4.2 Preparation Of Probecable For Multiple Blasthole Recording
1. Prepare the end of the PROBECABLE by using the wire cutters to remove
the insulation from the end. Then short the PROBECABLE by connecting
the shielding wire to the center conductor wire and twist them together.
Protect the connection well with electrical tape.
2. Start with the blasthole that is designed to detonate first of the multiple
holes to be recorded by the DataTrap II™ Data/VOD Recorder .
Using tape or wire, attach the short circuit end of the PROBECABLE
to the booster or to a rock, and lower the PROBECABLE into the hole.
Detonation cord downlines may damage the PROBECABLE or cause side
initiation of the bulk explosive. When initiating with detonation cord,
attach the
PROBECABLE to a rock and lower it on the side of the hole
opposite to the detonation cord downline.
3. Run the PROBECABLE between the first hole and the second hole leaving
sufficient slack between the holes to allow for ground movement between
the delayed holes. Excess
PROBECABLE between holes is not a concern
for the DataTrap II™ Data/VOD Recorder .
4. Each blasthole following the first hole will require a doubled length of PROBECABLE in order to form a continuous circuit throughout
the blast. There are two common methods of lowering a doubled length of PROBECABLE in these holes. The first and simplest method
is to run the PROBECABLE through a wire loop that has been tied or taped around a rock or booster. This allows the rock to slide
along the PROBECABLE as the PROBECABLE is lowered into the hole, until the rock reaches the bottom of the hole. The second method
is to measure out the midpoint of the length of PROBECABLE that is to be lowered into the hole, and attach the rock or booster so that
it reaches the exactly the bottom of the hole when inserted.
5. After the last hole to be recorded has been loaded with PROBECABLE , the PROBECABLE can then be cut at the top of that hole.
6. Note the Unit Resistance of the probe by reading the value in ohm/m or ohm/ft from the MREL factory label on the spool of
PROBECABLE . Note the ohm/m value if the VOD is to be reported in m/s. Note the ohm/ft value if the VOD is to be reported in
ft/sec. The Unit Resistance information will be requested later by the DAS™ Data Acquisition Suite . When measured with a Blaster’s
galvanometer, the Probe Resistance should compare favorably with the calculated resistance of the PROBECABLE (Unit Resistance
multiplied by its length). If this is not the case then remove the length of PROBECABLE and reload another length into the hole.
7. The hole can now be loaded with explosives and stemming per usual procedure. Hold the PROBECABLE taut during the loading of
the explosive to avoid slack in the hole. If you will not be present during loading, tie the PROBECABLE taut around a hole marker
stake, or around a rock at the top of the borehole. After loading, you may wish to check the Probe Resistance with a digital Blaster’s
Galvanometer to ensure that no damage has occurred to the PROBECABLE .
8. Do not use a standard mulitmeter because they can put too much current through the cable.
9. At the top of the last hole, connect the
PROBECABLE to the coaxial cable using the wire cutters and electrical tape. The connection
Figure 3