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Built in Threshold on Omega 8000 built into sensitivity control

earthmansurfer

Active member
What do you all think regarding the Omega (relative to the Fisher F5) implementing the threshold into the sensitivity control?

I am confused on something regarding this. In the post below M. Hillis says the gain is from 1 to 70 and above 70 the threshold kicks in. Does the gain still increase after 70 or is it just the threshold that is increasing? (I've seen people post the latter). BTW - My Omega runs very quiet at even 99 sensitivity most of the time so I'm a bit perplexed by the term "threshold" here as I thought threshold was a hum and not just boosting weak audio signals. I imagine testing would need to be done to verify this.

This post taken from Mike Hillis goes into the details: Full F5 vs. Omega Post Interesting post btw. He favors the F5 so it's biased but there is still lots of good info on the Omega 8000. Here is part II F5 vs Omega 8000 part II

Mike Hillis said:
The Omega manual states that the Sensitivity control combines the Gain and threshold controls into one rotary dial. There is no independent threshold control on the Omega. The Gain settings are located in the range of 1 through 70 and settings above 70 through 99 activate the threshold settings. The threshold range of the Sensitivity setting increases the audio output making the weaker signals easier louder and easier to hear much like the +1 through +9 Threshold settings on the F5. This has its pluses and minuses. For one thing, the gain setting has a finer adjustment range and the high gain settings are very sensitive. If you can get this high in the field, moving up into the threshold range will give you an increased audio output on the weaker signals. The bad thing is that not only are all signals multiplied by the high gain settings to get here in the first place, they are also made louder by the threshold feature. The stability enjoyed by the F5 combinations are not available on the Omega. It is still as sensitive, just not as adaptable. Stop and think about this. Before I can use the threshold feature of the Sensitivity control I have to max out the Gain setting. There is no flexibility. I only have a on or off arrangement. The added benefits of the threshold are only available if I can max out the gain. Second, I can only increase the threshold settings. I cant decrease them. Additionally, there is no sensitivity control for the all metal auto tune mode on the Omega. In the all metal mode, The sensitivity control now becomes a Threshold control. Raising the sensitivity settings increase the audio volume of the threshold hum, high sensitivity setting = very loud hum.
 
made using the Sensitivity control on your Omega 8000. The variable gain/sensitivity for the Discriminate mode is a somewhat different function and, yes, it can be run at '99' when there isn't any nearby EMI. I always run my Sensitivity as high as possible while remaining stable, but only in the motion-based Discriminate mode.

In the auto-tuned All Metal mode, the Omega will be operating at "full gain possible" when you have adjusted for a slight audio 'hum' or Threshold setting. That will often be somewhere between about '68' and '72' depending upon the headphones used or outside ambient noise if you're relying on the detector's speaker w/o headphones. When I hunt in All Metal, which I do from time-to-time, I'm usually set at about '69'-'70'-'71' as it's all rather close and it works fine for me. Roughly, you can just call it '70' and be close.

Note that on Page 12 of your Owner's manual, under Sensitivity, sub-part d. it states:

"The Sensitivity has two ranges. From 0 to 70, the sensitivity increases on a linear scale. Above 71 (I'm sure they mean from 71 and above) the sensitivity threshold level starts changing. At values greater than 70, some internal circuit noise will be noticed. the higher the number, the higher the background "static" will be. many seasoned detectorists prefer to operate at high sensitivity level, with the accompanying noise. They call this "working into the noise." When some background level of noise is audible, small changes in the volume and tone will denote the presence of buried metal."

Note, however, that it doesn't state which operating "mode" you are in when this adjustment is made, exceptthe next category is the Discriminate/AT Autotune description and the a. instruction tells you to:

"Click counterclockwise to the AT icon to enter the Auto Tune mode."

So, as I am working on an operators manual of my own design, I hope to clarify and make sure everything is clear. By the Page 12 suggestions, at this point, it is a little confusing to many I'm sure. As a rule I describe the Sensitivity control a bit differently and the above description would be applied to searches made in the Discriminate mode. As instructed on Page #11 under "Powering Up" they suggest keeping the sensitivity below 70 until you become comfortable with the detector's operation. Again, this is because most people will search mainly in the motion Discriminate mode (generally "silent search" unless they run the gain (sensitivity) level too high which can cause noise or static or instability.

When hunting in the motion-based Discriminate mode, the Sensitivity control setting will not only determine the maximum depth of detection, but higher settings (as you can easily note with some bench or air-testing) will also saturate the overall signal response and it will thus be less 'modulated.' Many like to hunt at a lower to mid-range Sensitivity setting because they like to hear the more modulated audio. That's what I like about hunting in the d2 Audio option. When searching using the d4 Tone ID selection, I favor the highest Sensitivity simply because (due to my hearing) I like the more saturated response from most detectable targets in d4.

Now, as for that "THRESHOLD" matter you asked about. Yes, a Threshold is what we associate with the All Metal (Auto-Tune) mode and if you refer to Page #15 in the Owner's Manual, under "How to Ground Balance your detector:" it states:

"1. Turn the detector On and select the AT (Auto-Tune or All Metal ) mode."

Then, in #3, you:

"Rotate the SENS knob to a point where you hear a slight background hum."

This instruction is easily missed by many readers as it is brief and since two functions are tied into the use of the Sensitivity control, many can easily get lost.

So, there you go. In the Disc. mode, using any of the 4 Audio/Tone ID options, the Sensitivity control can be increased as low as you desire for reduced depth and limited target response, or as high as you choose as long as there isn't any "noise" or "chatter." Using higher Sensitivity settings, especially above about '70' will add to the saturation of the audio response you hear from mid-to-deep targets.

In the All Metal Auto-Tune mode, as explained in the manual, you will be able to achieve maximum target detection depth. This is best achieved if you set the detector for a "nice and proper" slight audio threshold hum, and that is accomplished by adjusting the Sensitivity control. It's just a function that is tied in with that control and is NOT a sensitivity adjustment as you're used to.

With the T2, for example, you have a "Hum' or Threshold level adjustment AND a Sensitivity adjustment. Actually, you have a Sensitivity adjustment for BOTH the All Metal as well as the Discriminate mode so they can be set differently. With your Omega, just presume that if you choose the AT All Metal mode you're "factory perset" for maximum Sensitivity (to get the best depth possible) and your influence on that is to adjust the Threshold or Hum level. Since the Sensitivity control is not functioning as such in that mode, it is used to set the All Metal Threshold level.

So, I hoped this has helped anyone,and since I am a slow keyboard operator and short on time (I'm headed out to detect shortly :) ) I don't have time to proof read it. Hopefully, I didn't error too much and it's clear as mud ... I mean water.

Monte
 
Sorry Monte, but this information that you posted is so valuable (to me at least) that i wanted to post this POST AGAIN so that those new to the Omega would read this and HOPEFULLY help them to understand this awesome machine a little better!
 
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