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Few Additioal Details
Posted by: Eric Foster (---.proxy.aol.com)
Date: March 19, 2005 04:52AM
Hi bbsailor,
The 5uS is measured from the start of the transmitter switch off, so it includes the high voltage flyback time. The scope was externally triggered by the drive pulse to the Mosfet.
The shielded coil plus cable resonant frequency is 555kHz. This is measured by inducing a pulse from another coil, so it does not include any extra capacitance contribution from the electronics.
Coil inductance is 344uH and coil resistance 3.8 ohms, inclusive of cable.
The transmitter pulse is 20uS wide and the two sample pulses 5uS wide, when running at the 5uS delay. TX p.p.s. is 20,000. At the other end of the delay control, the TX is 60uS wide, with delay and samples at 15uS, and p.p.s. is 6500.
The considerable reduction in useable sample pulse delay is the sum of attention to three areas. 1) the coil 2) transmitter output and drive circuits 3) front end amplifier. At this point in time, this detector is purely experimental, just to see if the limits can be pushed out a bit further.
Eric.
Posted By KT 315 In the did I measure self resonence properly
Thanks KT 315
Hi Green,
I had a chance to do the srf test with the input resistor removed. You were right about the input resistor acting like a damping resistor. It heats up pretty fast with no damping resistor installed.
I unhooked the Input on one side and made a loop with the probe end and I get the exact same srf as I do pulsing with a live coil. The only differance is the voltage on the coil, the SRF is constant both ways. But it was good to find out this coil will still operate without a damping resistor. Coil is hitting a nickle both damped and undamped first sign at 14 inches hard by 12 its a 7" od coil not too shabby so far.
This is the SRF with the probe not touching the coil just held close.
This is the coil Undamped before I cut the input resistor.
This is the coil Damped at 2.47k measured from the fet gate.
.
I have my MPP set to 5us min sample on the delay so far this coil is more stable less chatty down that low than other coils I have tested so far.
Once I get home a settle in Ill test the other coils and some shielding see what final speed of this coil with this type of wire if spacing did anything..
Thanks
Posted by: Eric Foster (---.proxy.aol.com)
Date: March 19, 2005 04:52AM
Hi bbsailor,
The 5uS is measured from the start of the transmitter switch off, so it includes the high voltage flyback time. The scope was externally triggered by the drive pulse to the Mosfet.
The shielded coil plus cable resonant frequency is 555kHz. This is measured by inducing a pulse from another coil, so it does not include any extra capacitance contribution from the electronics.
Coil inductance is 344uH and coil resistance 3.8 ohms, inclusive of cable.
The transmitter pulse is 20uS wide and the two sample pulses 5uS wide, when running at the 5uS delay. TX p.p.s. is 20,000. At the other end of the delay control, the TX is 60uS wide, with delay and samples at 15uS, and p.p.s. is 6500.
The considerable reduction in useable sample pulse delay is the sum of attention to three areas. 1) the coil 2) transmitter output and drive circuits 3) front end amplifier. At this point in time, this detector is purely experimental, just to see if the limits can be pushed out a bit further.
Eric.
Posted By KT 315 In the did I measure self resonence properly
Thanks KT 315
Hi Green,
I had a chance to do the srf test with the input resistor removed. You were right about the input resistor acting like a damping resistor. It heats up pretty fast with no damping resistor installed.
I unhooked the Input on one side and made a loop with the probe end and I get the exact same srf as I do pulsing with a live coil. The only differance is the voltage on the coil, the SRF is constant both ways. But it was good to find out this coil will still operate without a damping resistor. Coil is hitting a nickle both damped and undamped first sign at 14 inches hard by 12 its a 7" od coil not too shabby so far.
This is the SRF with the probe not touching the coil just held close.
This is the coil Undamped before I cut the input resistor.
This is the coil Damped at 2.47k measured from the fet gate.
I have my MPP set to 5us min sample on the delay so far this coil is more stable less chatty down that low than other coils I have tested so far.
Once I get home a settle in Ill test the other coils and some shielding see what final speed of this coil with this type of wire if spacing did anything..
Thanks
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