Blasting Galvanometer or Blasting Ohmmeter

147

01:09:50

Repeated instructions about wiring explosives circuit, test explosive circuit with galvanometer, before lastly connecting batteries did not sound right.  Did the Army want to get the bomb builders blown up?

More research on Oil Field Safety Practice (RP 67) showed a special Blasting Galvanometer or Blasting Ohmmeter with current restricting limits is used.  Do not use regular ohm meter ( unless enough resistance has been added to line to get current below 200 milliamps or maybe 150 milliamps, or 10% of no-fire ratings of the detonators to be used).  Using resistor detonators is inherently safer than non- resistor detonators.

If any doubt that testing gear is safe, IMMEDIATELY TAKE IT OUT OF SERVICE AND TO A COMPETENT SERVICE FACILITY.

Two resistors on each side of battery is one current limiting method. The 275 milliohm resistor is where blasting cap goes.

published 9 years ago

GeoffEdwards

9 years ago

1. Galvanometer is extremely sensitive volt/milliameter, moving coil not powered. Presumably used to confirm circuit is completely dead with no stray leakage voltage in explosive side which could trigger when wires joined and trigger side to check switch is OFF when connecting. 2. Most digital multimeters (and analogue) will pass well below 200ma.

lmccoig

9 years ago

Confirming electric circuit exists was thrust of instructions. Non- electric detonators was shown as well.

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