CA1126382A - Distribution panel for connection of blasting circuits - Google Patents
Distribution panel for connection of blasting circuitsInfo
- Publication number
- CA1126382A CA1126382A CA316,876A CA316876A CA1126382A CA 1126382 A CA1126382 A CA 1126382A CA 316876 A CA316876 A CA 316876A CA 1126382 A CA1126382 A CA 1126382A
- Authority
- CA
- Canada
- Prior art keywords
- resistance
- pair
- detonators
- terminals
- series
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Measurement Of Current Or Voltage (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An electric distribution panel is provided for the initiation of a large number or series of electric blasting caps. The panel includes input terminals, output terminals connected in parallel to the input terminals and at least one threshold current conducting device in series between the terminals. use of the panel takes account of the resistance of the joint between each series of caps and hence overcomes current starvation.
An electric distribution panel is provided for the initiation of a large number or series of electric blasting caps. The panel includes input terminals, output terminals connected in parallel to the input terminals and at least one threshold current conducting device in series between the terminals. use of the panel takes account of the resistance of the joint between each series of caps and hence overcomes current starvation.
Description
~Z638Z
THIS invention relates to the connection of blasting circuits.
When a large number of detonators are to be used in a blast, the detonators are divided into sets wherein they are series connected to each other and the sets are connected in parallel to each other. Mining practice requires that a resistance measurement of each set of series connected detonators be made prior to the blast. To do this, one end of the set of series detonators, the resistance of which is being measured, is disconnected from the parallel combination and the resistance measurement is taken. However, such a measurement does not include the resistance of the joint between each set and the parallel combination and, although the resistance of the set may be within the specified limit, the resistance of the joint between a particular set and the parallel combination may be too high and this particular set will therefore suffer from current starvation during thè blast~
It is an object of the present invention to provide a distribution panel, which allows this problem to be overcome.
The invention provides a distribution panel, which includes a pair of input terminals, a plurality of pairs of output terminals connected in parallel to the pair - . ~
~lZ638Z
of input terminals and at least one threshold current conducting device connected in series between the input terminals and at least one pair of the output terminals.
Further according to the invention, each pair of output terminals has at least one threshold current conducting device connected in series between the pair of output terminals and the pair of input terminals.
The threshold device may be a zener diode with a suitable zener voltage.
Alternatively, the threshold device may consist of a pair of silicon diodes which are connected in parallel and back to back, that is, with opposed polarities.
The invention also provides a method of measuring the resistance of each set of a plurality of sets of series connected detonators connected in parallel to each other which includes the steps of isolating each set of series connec-ted detonators by means of a threshold current conducting device from the remaining sets and measuring the resistance of each set of series connected detonators by means of an ohm-meter with an output characteristic which is lower than the conduction threshold of the device.
The invention is further described by way of example with reference to the accompanying drawing, which illustrates the manner of use of a distribution panel 25 according to the invention~
- ~Z63~3Z
Referring to the drawing, a distribution panel 10 according to the invention includes a pair of input terminals 12 and a plurality of pairs of output terminals 14.
Each pair of ou-tput terminals has a zener diode 16 connected to one of its terminals and the output terminals are connected in parallel to the input terminals 12.
In use of the panel, a shot exploder 18 is connected to the input terminals. The shot exploder includes a capacitor 20 which is charged by suitable means, not shown, and a normally closed switch 22 which short-circuits the input terminals and which, when operated, connects the capacitor 20 to the input terminals.
Across each pair of output terminals 14, there are a plurality of series connected detonators 24.
The zener diodes have zener voltages of five volts.
Since each diode represents a very high resistance for - voltages below five volts in one direction, the resistance of any of the series connected detonators across one of the pairs of output terminals 14 may be measured without disconnecting it from the distribution panel by using a suitable ohm-meter with an open circuit output, which is less than five volts. The plurality of the zener diode connections is such that the firing current, which is generated by the discharge of the capacitor 20, passes through the forward biassed diode during blasting. The - loss of firing power is negligible as the voltage drop across each diode is less than one volt.
~12638Z
The ohm-meter which is used rnus-t be connected to the distribution panel output terminals with the correct polarity. This can be tested, for example, by disconnecting the detonators from the output terminals to which the ohm-meter is connectea. The ohm-meter should then read in-finity. If it does not, the ohm-meter leads should be reversed, whereupon the ohm-meter should read the resistance of detonators connected to the appropriate output terminals.
The zener diodes are suitably rated to carry the firing current for each series of detonators. When a modern digital ohm-meter, which has a very low output current, is employed for the resistance measurement, the voltage across the measured blasting series is of the order of 10 mV. The zener diodes, which are relatively expensive, may then be replaced by back to back parallel connected silicon diodes.
Since a silicon diode has a forward volt drop of about 0,5 volts, the voltage across each set of series connected detonators is limited to this value.
The distribution panel of the invention therefore permits resistance measurements to be made of the series connected detonators without the breaking and subsequent re-making of connections. The panel offers the further advanta3e that static, or voltages which are generated in any other way and which may be developed across the distribution panel output terminals, are limited to the threshold values of the conducting devices used. For example, if use is made of five volt zener diodes, the 1~2638Z
static voltage across any pair of output terminals will not exceed five volts provided that the input terminals 12 are shorted. Since the switch 22 is normally closed, this condition is ensured.
THIS invention relates to the connection of blasting circuits.
When a large number of detonators are to be used in a blast, the detonators are divided into sets wherein they are series connected to each other and the sets are connected in parallel to each other. Mining practice requires that a resistance measurement of each set of series connected detonators be made prior to the blast. To do this, one end of the set of series detonators, the resistance of which is being measured, is disconnected from the parallel combination and the resistance measurement is taken. However, such a measurement does not include the resistance of the joint between each set and the parallel combination and, although the resistance of the set may be within the specified limit, the resistance of the joint between a particular set and the parallel combination may be too high and this particular set will therefore suffer from current starvation during thè blast~
It is an object of the present invention to provide a distribution panel, which allows this problem to be overcome.
The invention provides a distribution panel, which includes a pair of input terminals, a plurality of pairs of output terminals connected in parallel to the pair - . ~
~lZ638Z
of input terminals and at least one threshold current conducting device connected in series between the input terminals and at least one pair of the output terminals.
Further according to the invention, each pair of output terminals has at least one threshold current conducting device connected in series between the pair of output terminals and the pair of input terminals.
The threshold device may be a zener diode with a suitable zener voltage.
Alternatively, the threshold device may consist of a pair of silicon diodes which are connected in parallel and back to back, that is, with opposed polarities.
The invention also provides a method of measuring the resistance of each set of a plurality of sets of series connected detonators connected in parallel to each other which includes the steps of isolating each set of series connec-ted detonators by means of a threshold current conducting device from the remaining sets and measuring the resistance of each set of series connected detonators by means of an ohm-meter with an output characteristic which is lower than the conduction threshold of the device.
The invention is further described by way of example with reference to the accompanying drawing, which illustrates the manner of use of a distribution panel 25 according to the invention~
- ~Z63~3Z
Referring to the drawing, a distribution panel 10 according to the invention includes a pair of input terminals 12 and a plurality of pairs of output terminals 14.
Each pair of ou-tput terminals has a zener diode 16 connected to one of its terminals and the output terminals are connected in parallel to the input terminals 12.
In use of the panel, a shot exploder 18 is connected to the input terminals. The shot exploder includes a capacitor 20 which is charged by suitable means, not shown, and a normally closed switch 22 which short-circuits the input terminals and which, when operated, connects the capacitor 20 to the input terminals.
Across each pair of output terminals 14, there are a plurality of series connected detonators 24.
The zener diodes have zener voltages of five volts.
Since each diode represents a very high resistance for - voltages below five volts in one direction, the resistance of any of the series connected detonators across one of the pairs of output terminals 14 may be measured without disconnecting it from the distribution panel by using a suitable ohm-meter with an open circuit output, which is less than five volts. The plurality of the zener diode connections is such that the firing current, which is generated by the discharge of the capacitor 20, passes through the forward biassed diode during blasting. The - loss of firing power is negligible as the voltage drop across each diode is less than one volt.
~12638Z
The ohm-meter which is used rnus-t be connected to the distribution panel output terminals with the correct polarity. This can be tested, for example, by disconnecting the detonators from the output terminals to which the ohm-meter is connectea. The ohm-meter should then read in-finity. If it does not, the ohm-meter leads should be reversed, whereupon the ohm-meter should read the resistance of detonators connected to the appropriate output terminals.
The zener diodes are suitably rated to carry the firing current for each series of detonators. When a modern digital ohm-meter, which has a very low output current, is employed for the resistance measurement, the voltage across the measured blasting series is of the order of 10 mV. The zener diodes, which are relatively expensive, may then be replaced by back to back parallel connected silicon diodes.
Since a silicon diode has a forward volt drop of about 0,5 volts, the voltage across each set of series connected detonators is limited to this value.
The distribution panel of the invention therefore permits resistance measurements to be made of the series connected detonators without the breaking and subsequent re-making of connections. The panel offers the further advanta3e that static, or voltages which are generated in any other way and which may be developed across the distribution panel output terminals, are limited to the threshold values of the conducting devices used. For example, if use is made of five volt zener diodes, the 1~2638Z
static voltage across any pair of output terminals will not exceed five volts provided that the input terminals 12 are shorted. Since the switch 22 is normally closed, this condition is ensured.
Claims (9)
1. A resistance measuring means for measuring the resistance of each set of a plurality of sets of series-connected detonators connected in parallel to each other and for distributing detonating current to the said sets of detona-tors, which comprises:
(a) a pair of input terminals connectable to a source of detonating current;
(b) a plurality of threshold conducting devices; and (c) a plurality of pairs of output terminals each connectable to a set of detonators with first terminals of all the pairs of output terminals each being connected via separate ones of the conducting devices to a first terminal of the pair of input terminals and with the second terminals of the pairs of output terminals being connected to the second terminal of the pair of input terminals.
(a) a pair of input terminals connectable to a source of detonating current;
(b) a plurality of threshold conducting devices; and (c) a plurality of pairs of output terminals each connectable to a set of detonators with first terminals of all the pairs of output terminals each being connected via separate ones of the conducting devices to a first terminal of the pair of input terminals and with the second terminals of the pairs of output terminals being connected to the second terminal of the pair of input terminals.
2. A resistance measuring means as claimed in Claim 1 wherein the second output terminals are directly electrically connected with the second input terminal.
3. A resistance measuring means as claimed in Claim 1 wherein each threshold current conducting device is a zener diode.
4. A resistance measuring means as claimed in Claim 1 wherein each threshold current conducting device consists of a pair of silicon diodes connected in parallel to each other with opposed polarities.
5. A resistance measuring means as claimed in Claim 1 wherein the pair of input terminals is connected to a normally closed switching device.
6, A resistance measuring means as claimed in Claim 5 wherein the switching device is a shot exploder.
7. A resistance measuring means as claimed in Claim 1 wherein each pair of output terminals is connected to a plurality of detonators in series.
8. A resistance measuring means as claimed in Claim 1 in combination with an ohm-meter arranged to measure the resistance across each pair of output terminals in turn.
9. A method of measuring the resistance of each set of a prurality of sets of series connected detonators connected in parallel to each other comprising the steps of isolating each set of series connected detonators from the remaining sets by means of a threshold current conducting device and measuring the resistance of each of the said isolated sets of series connected detonators by means of an ohm-meter having an output characteristic which is lower than the conduction threshold of the device.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ZA00780906A ZA78906B (en) | 1978-02-16 | 1978-02-16 | Distribution panel for connection of blasting circuits |
| ZA78/0906 | 1978-02-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1126382A true CA1126382A (en) | 1982-06-22 |
Family
ID=25572592
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA316,876A Expired CA1126382A (en) | 1978-02-16 | 1978-11-24 | Distribution panel for connection of blasting circuits |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1126382A (en) |
| ZA (1) | ZA78906B (en) |
-
1978
- 1978-02-16 ZA ZA00780906A patent/ZA78906B/en unknown
- 1978-11-24 CA CA316,876A patent/CA1126382A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| ZA78906B (en) | 1979-09-26 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4280097A (en) | Isolated DC voltage monitoring system | |
| US1795972A (en) | Charging device for electrical fuses | |
| GB1464477A (en) | Circuitry for analysins spark ignition voltages | |
| US2814774A (en) | Continuity and short tester | |
| US3675578A (en) | Apparatus for testing and detonating blasting caps | |
| US4301403A (en) | Electrical circuit testing | |
| CA1126382A (en) | Distribution panel for connection of blasting circuits | |
| GB924432A (en) | Improved means for the identification of conductors in electric cables or circuits | |
| JPS6453045A (en) | Device for inspecting at least two electric load of automobile | |
| US2645754A (en) | Low voltage neon shorts tester | |
| US3521155A (en) | Ignition amplifier and coil tester | |
| US3683234A (en) | Protective device comprising a plurality of serially connected spark gaps | |
| US3878790A (en) | Seismic blaster circuit | |
| US4095172A (en) | Vehicle antenna tester | |
| US3624503A (en) | Means and method for detecting stray electrical energy, above a predetermined level, on a conductor | |
| US2452614A (en) | Electrical test circuit | |
| SU1153298A2 (en) | Device for pre-burning and testing flash modulator tubes | |
| US3899737A (en) | Apparatus for testing alternator diodes | |
| SU1551979A1 (en) | Simulator of discrete increment of resistance of strain gauge | |
| SU1087928A1 (en) | Device for pre-burning and testing pulse modulator tubes | |
| SU1698799A1 (en) | Electric circuit impedometer | |
| SU1705772A1 (en) | Device for locating short-circuiting in electric circuits | |
| SU254370A1 (en) | Condensing Blasting Device | |
| SU1751702A1 (en) | Apparatus for nondestructive checking of electrical strength of cable insulation | |
| SU1712890A1 (en) | Device to measure high voltages |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |