A couple of days ago I was surveying a small lot from a small subdivision done in 2011. I didn't know it when I started, but apparently the front of the lots were originally "ditch-to-drain". Sometime after the subdivision was developed, the ditch was filled in. Fortunately for me, when the fill was added, it did not disturb the front stakes, only covered them. The first one that I found was a 1/2" iron rod with ID cap, 16" deep. The second was a 1/2" iron rod with ID cap, 22" deep. I found both using the J-Tip.
I use the digital readout quite a bit to see the polarity and the strength of the signal. Unlike other detectors, the tones are used to alert the user to a magnetic signal and are scaled based on the current highest magnetic signal. This is to help with pinpointing an isolated signal. In areas of multiple signals, the tones are less useful and the digital readout on the LS becomes more significant. The digital scale "zeros" at an arbitrary value of 100. The sensors have a noise of about 1. So you might see 99 or 101 without changing the magnetic field surrounding the J-Tip. When the signal dips below 100, the polarity is negative. When the signal is above 100, the polarity is positive.
The 5PLS Team has done a lot of testing of the J-Tip with a lot of materials at various depths over the last several months. One thing I can share is experience that isn't just based on the J-Tip, but also on experience with other manufacturers as well. The magnetic field of two identical objects may not be aligned in the same way. I've seen 1/2" rebar give a strong signal and I've seen it give a very poor signal, or no signal at all. Sometimes, with a Schonstedt, I found rebar when the sound would go dead. There would be a slight hum around the rebar, but when I would be right over the rebar, the hum would go silent. For this reason, it's important for a surveyor to use a locator as a guide, but not the final authority on whether a stake is in the ground or not (a shovel still reigns supreme here). I grabbed 4 rebar from a bundle early in testing. Some were showing 200 or more while one was 4. The strength may indicate the size or depth of the object, but not always.
Back to the J-Tip, using our arbitrary scale, I've seen the values reach 200-700 when the J-Tip was on top of the rebar. The scale isn't linear. Close to 100 (neutral) any change is very big, but as the values change much from 100, the changes are less significant. A change in 200-300 isn't much change, where a change from 5 to 20 is very big. In the case of these two rebar, the 16" rebar showed a change of +4. The 22" rebar showed a change of +3. To the uninitiated, it might be that a signal like that would go unnoticed, but it is important for J-Tip users to become students of these values. You've likely never been presented with anything like it before. Small changes in values at the lower end of the scale represent big signals.
One more note. The scale for negative polarity is different from the scale for positive polarity. A -10 (which would be a 90) is much stronger than a +10 (which would be a 110). Sometimes a monument may have the negative end up, so you shouldn't dismiss all negative signals. Sometimes, when working along a fence, you may notice that the fence has a negative polarity, which makes it a little easier to ignore (but again, you can't always ignore it). The PLS team has also noticed that objects that are laying on their side in the search area can be identified by a strong positive signal with a strong negative signal a few inches away (or whatever length the object is). A screwdriver will give a positive signal at one end and a negative signal at the other. The two signals with be separated by the length of the screwdriver.
16" Deep (J-Tip signal +4):
How I left it:
22" Deep (J-Tip signal +3):
How I left it: