Demon blade count - manual error?
 

Both the SC and DW manuals say that in DEMON, the leftmost line is the shaft and the remaining lines are for each blade.

However, it appears to me that the number of lines in DEMON equals the blade count; NOT the blade count + 1.

Comments?

Thanks.

I'd say you're right. I've used demon to find the speed for VISID cargo ships and such, and they've always showed the right ammount of blades. So it looks like you found a mistake in the manual.

:up:

Yes .. you are right. Number of lines is number of blades. Sometimes not all lines can be visible, I've heard. But I have never seen it. And if you ever work with real DEMON, beware, it works quite different, as it was already discussed here, look for DEMON in post title.

thats right the number of blades shown in the Demon is the number of blades your contact have.

Sometimes not all blades are displayed. That happens to me mostly when i track submerged target from greater distances. (using LWAMI)

But there is still one thing im not sure. When i try to get the speed of a target where i get a strong signal from. Should i mark the left or the right corner of the first Demon line or maybe in the middle of that line?

I have done some experiments for this problem and crosschecked my DEMON with show truth on but i didnt get a rule for that.

blade count
 

I never played DW or SC but I have 'experience' in the field of sonar. I don't know what the sonar displays look like in game or anything. Basically what you said is the correct display. The first 'bright' line would represent your shaft RPM. But it is also the first blade. The other four blades (of a five bladed contact) would pass the same point, thus creating the other lines, and when the first blade returns to the same point, that makes one revolution of the shaft, but still five blades worth of tonals. Then the pattern continues" SHAFT, blade, blade, blade blade, SHAFT, blade, blade, blade blade."

Once again, I don't know how DW or SC is with displays, but IRT calculating speed, I know you need to get the spacing of the harmonics in the blade rate. To do that, you measure from the edge of one harmonic, to the sam edge of the next. Whether using left, right, or center, as long as you are consistent, the spacing will be the same.

Its quite easy actually, choose the lowest frequency setting, put your cursor over the leftmost frequency line it and it will give you the exact speed.
In this case it doesn't matter if you mark the left, middle or right corner since you'll get only one speed value.
With other choices of frequency setting normally you'll get a little ambiguity between the left and right corner (1-2 knots).