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ive been looking at the whites tdi pro on youtube and it seems like a great machine...i wondered how much current does the tdi pro draw from the 14v battery pack ???? cause if the battery pack is 5 amp hour and the running time is 8 hours...the detector must be using a lot of power.
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The TDI has a pulse frequency between 2.5kHz and 3kHz. If we assume the detector is set at 2.5kHz and the TX pulse width is 50us, we have a pulse current of 5A (ignoring the extra current drawn by the other electronics).Originally posted by daverave View Post
If you want to work this out backwards:
5A coil current / 8 = 625mA average current.
5Ah / 625mA = 8 hours detecting time. -
i measured the current from surf dual field and that was no more than about 60 ma so why the tdi so current heavy and only 8 hours running time ?????Comment
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Tell me, why are people so concerned about current consumption? As long as there is enough power in your battery to detect all day, you go home or back to your car put it on the charger and your ready to go again. More current in pi allows it to stimulate bigger targets better at depth, no point walking away from good targets not knowing they were even there in the first place cause your detector did not pick it up!
Cheers MickComment
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As a consequence of the 6th power law, you need a large increase in TX power just to gain a few inches in depth. In this case it looks like the TDI is using about 10 times the average current of the Surf-PI, and as a result achieves greater depth. Also, the TDI incorporates a ground balance feature, which will produce a reduction in the target signal due to the GB sample being subtracted from the main sample. Hence extra power is needed to compensate. Unfortunately you're up against the laws of physics.Originally posted by daverave View PostComment
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i still cannot see why they need to use 600ma....my first pulse detector i made uses 120ma and on a nickel half crown i can get 22" and on a small 9ct gold ring 20" in air...unless the extra power that the tdi uses is somehow for small nugget detection....i wonder what the in air depth is for 18ct & 22ct gold rings using the tdi pro...anyone know ????Comment
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Re: post #5
It's like the song by The Clash - "I Fought The Laws Of Physics And The Laws Won"...Comment
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im still in amazement why a tdi draws 625ma and a dual field draws around 60ma and the difference in depth is only several inches...why is it that my detector can do 22" on a nickel coin drawing only 120ma and a tdi draws 5 times more current and can do about 18" on a nickel...im a bit confused.Comment
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A-lot of the current draw will be related to all the electronics used on the receive side and microprocessor.Comment
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Are you saying the Surf-PI detects a nickel deeper than the TDI?Originally posted by daverave View PostComment
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my surf pi has been modified to work at higher frequency and gain and ive just shielded the pcb and my in air depth test on a british half crown nickel is 22" and my 9ct gold ring is now giving me a depth of 20" and im only using about 120 ma total.Comment
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I don't think the TDI's peak coil current would be 5A.Originally posted by Qiaozhi View Post
Assuming a 14v supply, coil L = 300uH, total coil circuit R = 0.6 ohms then a 50usec pulse would only give 2.22A peak coil current. We would need a 120usec pulse to get 5A.
If the TDI had the same total coil circuit R as the GS4 (~6.25 ohms) then the 50 usec pulse would only give 1.45A and the 120 usec pulse would drop to 2A.Comment
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You guys are getting all confused, and comparing kiwi fruit with melons.
DaveRave is talking about a cupro-nickel Half-Crown, a dirty great big 14 gram, 32mm coin.
The "nickel" is a US 5 cent cupro-nickel coin, that is a more modest 5 gram, 21mm.
If Dave wants to test his machine but hasn't got a US nickel, a shilling, or early large pre-1991 decimal 5 pence is a pretty close match.Comment
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i have just ordered a us nickel from ebay and will test this soon to see what depth i get on that.Comment
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