bklein Posted May 11, 2019 Share Posted May 11, 2019 Has someone verified that sample timing stays constant with battery voltage change? On lesser pi’s it moves. Link to comment Share on other sites More sharing options...
Jim in Idaho Posted May 15, 2019 Share Posted May 15, 2019 I've never checked mine, but find that interesting. Mine was built in '13. Do you have a diagram for the coil connector? I'd like to check mine. Something's fishy, for sure, as the voltage clearly makes a big difference. It's possible, because the voltage pulses at 100kh, that you can't read the voltage difference, except with a synchroscope, or other similar device. Jim 1 Link to comment Share on other sites More sharing options...
auminesweeper Posted May 15, 2019 Share Posted May 15, 2019 20 minutes ago, Jim in Idaho said: I've never checked mine, but find that interesting. Mine was built in '13. Do you have a diagram for the coil connector? I'd like to check mine. Something's fishy, for sure, as the voltage clearly makes a big difference. It's possible, because the voltage pulses at 100kh, that you can't read the voltage difference, except with a synchroscope, or other similar device. Jim Yep so was mine a 2013 Jim, I don't know how digger bob got is to see his tiny test pieces in that video but mine wouldn't see them, It ran as smooth as silk even with a thunder storm going on right about the house Nothing phased my TDI SL, all it took was a minute tweak of the Tune knob and it was good as gold, My 3500 didn't like storms 100 to 200 miles away but the SL has the best threshold ever put in a detector. 1 Link to comment Share on other sites More sharing options...
Mark Gillespie Posted May 15, 2019 Author Share Posted May 15, 2019 I used a calibrated, Fluke TRUE RMS volt meter for my measurements. Link to comment Share on other sites More sharing options...
Jim in Idaho Posted May 15, 2019 Share Posted May 15, 2019 1 hour ago, Mark Gillespie said: I used a calibrated, Fluke TRUE RMS volt meter for my measurements. I think, to use a voltmeter, you'd have to put a capacitor across the connections to get a true reading. I'm not sure about the capacitance needed...maybe 5mfd? Jim Link to comment Share on other sites More sharing options...
Jim in Idaho Posted May 15, 2019 Share Posted May 15, 2019 3 hours ago, auminesweeper said: Yep so was mine a 2013 Jim, I don't know how digger bob got is to see his tiny test pieces in that video but mine wouldn't see them, It ran as smooth as silk even with a thunder storm going on right about the house Nothing phased my TDI SL, all it took was a minute tweak of the Tune knob and it was good as gold, My 3500 didn't like storms 100 to 200 miles away but the SL has the best threshold ever put in a detector. With the 12"DF, and 16.8 v battery, mine will easily see a 1 grain gold bar at 3" in an air test, John. Might do even better with my NF 8x6 Sadie, but I haven't tested that coil. Jim Link to comment Share on other sites More sharing options...
auminesweeper Posted May 15, 2019 Share Posted May 15, 2019 2 hours ago, Jim in Idaho said: With the 12"DF, and 16.8 v battery, mine will easily see a 1 grain gold bar at 3" in an air test, John. Might do even better with my NF 8x6 Sadie, but I haven't tested that coil. Jim Well Jim mine would not see an 0.17 gram bit which is equal to just over 3 Grains with the 12" DF coil or the 7.5 DF coil not even with it sitting on the coil, regardless of the battery voltage. 1 Link to comment Share on other sites More sharing options...
Jim in Idaho Posted May 16, 2019 Share Posted May 16, 2019 I just tested the voltage output on mine, and it tracks perfectly with the battery pack voltage. With the 4 cell pack at 14.53v, I got 6.29v of output to the coil, and with the 3cell pack at 12.03v, I got 5.3v of output. So the higher battery voltage does push more current through the coil on mine. Thus a stronger magnetic pulse going into the ground. I figured out the correct terminals by using my inductance meter to see which terminals showed a coil across them. Looking at the connector, with the gap at the bottom, the correct terminals are the second from the left, and the second from the right. Inductance on both the NF Sadie 8 x 6, and the Super Pulse 350 14 x 9 showed 1.4 micro-henrys. Jim 1 Link to comment Share on other sites More sharing options...
Mark Gillespie Posted May 16, 2019 Author Share Posted May 16, 2019 10 hours ago, Jim in Idaho said: I just tested the voltage output on mine, and it tracks perfectly with the battery pack voltage. With the 4 cell pack at 14.53v, I got 6.29v of output to the coil, and with the 3cell pack at 12.03v, I got 5.3v of output. So the higher battery voltage does push more current through the coil on mine. Thus a stronger magnetic pulse going into the ground. I figured out the correct terminals by using my inductance meter to see which terminals showed a coil across them. Looking at the connector, with the gap at the bottom, the correct terminals are the second from the left, and the second from the right. Inductance on both the NF Sadie 8 x 6, and the Super Pulse 350 14 x 9 showed 1.4 micro-henrys. Jim Very interesting Jim. What device are you using to measure the voltage? I was using a calibrated Fluke True RMS and was measuring directly from the TX output on the board. All this said I noticed a very large difference in voltage from a complete counter clockwise frequency offset to a complete clockwise setting. Even though there was a large difference in output voltage I didn't see any extra air test advantage. The manual states this feature function is "This control makes small adjustments to the transmitter pulse rate". I was guessing a small shift in the frequencies and wasn't expecting the voltage span. Now you have me to wondering if the inductance of my coils might be different than yours because if the inductance is quite a bit larger (value) that would limit the current flow considerably. Link to comment Share on other sites More sharing options...
Jim in Idaho Posted May 16, 2019 Share Posted May 16, 2019 I'm measuring mine with a digital multimeter set on A/C volts. On the frequency, I'm seeing, with the 14.5v pack, 6.05v on the low, and 6.54 on the high. MIddle was 6.29. I'd be surprised if your coils have much difference in inductance, but it's possible. EDIT: I just did the inductance test on the 12"DF and got the exact same reading of 1.4 microhenrys. I assume that is the design inductance for the coils for TDI's. and probably the other brands of PI's. But, I don't know this to be fact. Jim 1 Link to comment Share on other sites More sharing options...
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