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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Posted to sci.electronics.design,sci.electronics.repair,sci.electronics.equipment
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MassiveProng wrote:
On Sun, 04 Mar 2007 10:11:09 GMT, Robert Baer Gave us: Here is a good "trick" to measure low currents with your DVM. Make a switchable shunt box with (at least) the following full scale ranges: 200nA (shunt resistor 1.11 megs), 2uA (shunt resistor 101K), 20uA (shunt resistor 10.0K), 200uA (shunt resistor 1.00K). Put a twisted pair of leads (red, black) with banana plugs (red, black) running out of the box via a small grommet, to plug into your DVM set to the 200mV scale; a pair of (red, black) banana jacks with 0.75 "spacing is mounted on the box for your test leads. Hint: add to the legend the parallel resistance of the system (200nA/1M, 2uA/100K, etc) as a reminder of the resistance of this current meter scheme. Added hint: the 200MV scale is good for 20nA full scale, just remember the meter resistance is 10 megs. Tell us, oh master... what does placing a 1,1 meg resistor in series with a circuit's power source do to the voltage presented to the circuit? http://www.google.com/search?hl=en&q=ohms+law It drops it like any other shunt would. If you were designing precision equipment, would you attempt to measure nA by using a .01Ohm resistor? Read Ed's post, he is right about being able to measure low currents that way, just as Robert is here. They just don't work if the current is varying over a wide range. But for static current measurements, THEY WILL WORK FINE. Shunt resistors are typically less than an ohm. Show me where ANYONE uses a 1.1 meg resistor os a current shunt. You've got to be kidding! Don't you design/build HV supplies? Tell me that your feedback circuits sense the full output voltage. HA HA HA I guess you don't use any micros, huh? Or do you just use a 100Ohm and .01Ohm resistive divider to sense that 50KV output? I'd really like to see that. |
#2
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Posted to sci.electronics.design,sci.electronics.repair,sci.electronics.equipment
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On Sun, 4 Mar 2007 13:31:17 -0600, "Anthony Fremont"
Gave us: It drops it like any other shunt would. Sub one ohm shunts affect the circuit very little. A ****ing 1.1 meg resistor is NEVER used as a shunt resistor, and would drastically affect ANY circuit. How can you be so thick? |
#3
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Posted to sci.electronics.design,sci.electronics.repair,sci.electronics.equipment
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MassiveProng wrote:
On Sun, 4 Mar 2007 13:31:17 -0600, "Anthony Fremont" Gave us: It drops it like any other shunt would. Sub one ohm shunts affect the circuit very little. A ****ing 1.1 meg resistor is NEVER used as a shunt resistor, and would drastically affect ANY circuit. How can you be so thick? No understanding of Ohms law wrt low currents. |
#4
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Posted to sci.electronics.design,sci.electronics.repair,sci.electronics.equipment
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On Sun, 4 Mar 2007 13:55:41 -0600, "Anthony Fremont"
Gave us: MassiveProng wrote: On Sun, 4 Mar 2007 13:31:17 -0600, "Anthony Fremont" Gave us: It drops it like any other shunt would. Sub one ohm shunts affect the circuit very little. A ****ing 1.1 meg resistor is NEVER used as a shunt resistor, and would drastically affect ANY circuit. How can you be so thick? No understanding of Ohms law wrt low currents. Well, then you should study more. |
#5
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Posted to sci.electronics.design,sci.electronics.repair,sci.electronics.equipment
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On Sun, 4 Mar 2007 13:31:17 -0600, "Anthony Fremont"
Gave us: Tell me that your feedback circuits sense the full output voltage. Voltage dividers are completely different than current shunts, you retarded ****. |
#6
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Posted to sci.electronics.design,sci.electronics.repair,sci.electronics.equipment
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MassiveProng wrote:
On Sun, 4 Mar 2007 13:31:17 -0600, "Anthony Fremont" Gave us: Tell me that your feedback circuits sense the full output voltage. Voltage dividers are completely different than current shunts, you retarded ****. No understanding of Ohms law. (now I see where Phil gets this from ;0) |
#7
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Posted to sci.electronics.design,sci.electronics.repair,sci.electronics.equipment
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On Sun, 4 Mar 2007 13:56:44 -0600, "Anthony Fremont"
Gave us: MassiveProng wrote: On Sun, 4 Mar 2007 13:31:17 -0600, "Anthony Fremont" Gave us: Tell me that your feedback circuits sense the full output voltage. Voltage dividers are completely different than current shunts, you retarded ****. No understanding of Ohms law. (now I see where Phil gets this from ;0) Then you should study more, dip****. |
#8
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Posted to sci.electronics.design,sci.electronics.repair,sci.electronics.equipment
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On Sun, 4 Mar 2007 13:31:17 -0600, "Anthony Fremont"
Gave us: HA HA HA I guess you don't use any micros, huh? Or do you just use a 100Ohm and .01Ohm resistive divider to sense that 50KV output? I'd really like to see that. You're a goddamned retard. This is about current shunts, not voltage feedback dividers, you stupid twit! You should go get with BAH. You are showing us that you are at her speed. |
#9
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Posted to sci.electronics.repair
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"Anthony Fremont" wrote in
: MassiveProng wrote: On Sun, 04 Mar 2007 10:11:09 GMT, Robert Baer Gave us: Here is a good "trick" to measure low currents with your DVM. Make a switchable shunt box with (at least) the following full scale ranges: 200nA (shunt resistor 1.11 megs), 2uA (shunt resistor 101K), 20uA (shunt resistor 10.0K), 200uA (shunt resistor 1.00K). Put a twisted pair of leads (red, black) with banana plugs (red, black) running out of the box via a small grommet, to plug into your DVM set to the 200mV scale; a pair of (red, black) banana jacks with 0.75 "spacing is mounted on the box for your test leads. Hint: add to the legend the parallel resistance of the system (200nA/1M, 2uA/100K, etc) as a reminder of the resistance of this current meter scheme. Added hint: the 200MV scale is good for 20nA full scale, just remember the meter resistance is 10 megs. Tell us, oh master... what does placing a 1,1 meg resistor in series with a circuit's power source do to the voltage presented to the circuit? http://www.google.com/search?hl=en&q=ohms+law It drops it like any other shunt would. all current measuring devices add resistance to the circuit,affecting it. Just like any DMM parallels its input resistance with what it's put across,loading the circuit under test. If you were designing precision equipment, would you attempt to measure nA by using a .01Ohm resistor? Read Ed's post, he is right about being able to measure low currents that way, just as Robert is here. They just don't work if the current is varying over a wide range. But for static current measurements, THEY WILL WORK FINE. Shunt resistors are typically less than an ohm. Show me where ANYONE uses a 1.1 meg resistor os a current shunt. (you use the 1.1 shunt value externally because the DMMs 10 Meg parallel resistance brings the effective R down to 1.0.) -- Jim Yanik jyanik at kua.net |
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