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Old 01-18-2014, 10:53 AM   #11
radioman
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Default Re: Inductive Throttle Sensor

There is something inside that ITS sensor besides wire. I spent several hours back and forth between two sensors measuring resistance between the tabs and I got different results with two types of ohmmeters but the same measurements on both sensors. I have used these two meters for decades troubleshooting . I began to suspect the digital meter was playing tricks so I dug into my resistor assortment and used several resistors to check both meters with and they read the correct value. I don't understand how a hall effect sensor could work with only two wires.
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Old 01-18-2014, 11:55 AM   #12
JohnnieB
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Default Re: Inductive Throttle Sensor

Quote:
Originally Posted by radioman View Post
I looked at the voltage with a scope and it was a sawtooth type waveform, not pure DC.
About 18kHz I'd wager. (Or whatever the PWM frequency is)

I was pretty sure it was something other than straight-line DC because pure DC only sees an inductor as a fixed value resistance except for the initial rise or fall. And I was pretty sure it was simply an inductor because it only has two wires.

Based on your username and the fact you have access to a scope, is it safe to presume you have some electronics training in your background?

I'm halfway decent at figuring out how things work, but how, exactly, the ITS (Inductive Throttle System) works has been eluding me since I got a cart.

The same, identical, ITS sensor is used with several different controllers, but the electronics that fed it and use the returned signal are inside the controller and while the throttle signal that is returned to the controller is altered by inserting an iron slug into the coil, increasing the inductance increases the voltage of the throttle signal on some controllers and decreases it on others.

The ITS on the Curtis 1206, 1206SX and 1206MX controllers (Series drive, DCS and PDS respectfully) all increase in voltage fed back to the controller when the slug in inserted (pedal pushed) while the voltage across the same ITS senor decreases when an Alltrax aftermarket controller is attached to it.

My guess is that the coil is being fed pulsed DC, which would become a sawtooth in an inductive circuit. How increasing the inductance of the coil mitigated the signal being returned to the controller would depend on whether the pulsed DC source was a constant current or a constant voltage source.

If possible, please describe (Amplitude - Polarity - Frequency - Etc.) the signals on J4 Pin-1 and on J4 Pin-2 with pedal up and pedal down.
I just might be able to figure out the physics of how the ITS works.
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Old 01-18-2014, 12:20 PM   #13
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Default Re: Inductive Throttle Sensor

I will get more data when the weather warms up. I am also confused about this part of the operation. But I don't understand why the resistance of the two different ITS devices would depend on the type ohm meter used to measure across it. A coil of wire would not act like this. 39K ohms with a old analog meter and 4 mega ohm with a Digital ohm meter. I have a problem imagining a wire long enough and thin enough to read 39,000 or 4,000,000ohms in a small package like the ITS. There has got to be something else inside it.
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Old 01-18-2014, 12:26 PM   #14
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Default Re: Inductive Throttle Sensor

Quote:
Originally Posted by radioman View Post
There is something inside that ITS sensor besides wire. I spent several hours back and forth between two sensors measuring resistance between the tabs and I got different results with two types of ohmmeters but the same measurements on both sensors. I have used these two meters for decades troubleshooting . I began to suspect the digital meter was playing tricks so I dug into my resistor assortment and used several resistors to check both meters with and they read the correct value. I don't understand how a hall effect sensor could work with only two wires.
You posted this while I was typing.
Sounds like you are bumping into the same brick walls I am.

I wouldn't surprised if there was more than just wire inside the sensor, but short of taking one apart, I cannot figure out what it is; And I don't have one to take apart.

Different types of Ohmmeters will produce different readings, even on pure ohmic resistance under some circumstances, but more often when there is a solid state device lurking in the circuit somewhere. But I didn't get a front to back ratio when I was measuring the ITS sensor in my cart.

------------
If anyone reading this post has a good or bad ITS sensor lying around collecting dust and is willing to donate it to the cause, I'll dissect it and find out what is in it.
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Old 01-18-2014, 12:50 PM   #15
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Default Re: Inductive Throttle Sensor

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Originally Posted by radioman View Post
I will get more data when the weather warms up. I am also confused about this part of the operation. But I don't understand why the resistance of the two different ITS devices would depend on the type ohm meter used to measure across it. A coil of wire would not act like this. 39K ohms with a old analog meter and 4 mega ohm with a Digital ohm meter. I have a problem imagining a wire long enough and thin enough to read 39,000 or 4,000,000ohms in a small package like the ITS. There has got to be something else inside it.
That doesn't make sense to me either and I have ran across some pretty weird stuff in my 50+ years of troubleshooting.

How, exactly, the things work doesn't really matter all that much since we do know what the inputs and outputs ought to be and can troubleshoot them as a black box, but I'm curious and I hate not knowing something that I ought to be able to figure out.

BTW: Welcome to BGW!!!!!

It gets a little deep around here occasionally, so keep your waders handy.
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Old 01-18-2014, 02:21 PM   #16
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Default Re: Inductive Throttle Sensor

Here is the answer of what is on the inside of the ITS. There is a motherboard that you can see.

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Old 01-18-2014, 02:29 PM   #17
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Default Re: Inductive Throttle Sensor

And it does have some little diodes in there and something u can turn but I had to use a torch and a small chizzle to get it apart. The whole inside is filled with that black stuff.
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Old 01-18-2014, 07:15 PM   #18
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Default Re: Inductive Throttle Sensor

Thanks for taking one apart.

Well we don't know what it is yet, but at least we know what it isn't.
It is not a simple coil of wire.

There are only to connections and with a PCB in the mix, we have to have an input and an output circuit, which takes at least three wires, unless they are multiplexing or using some other tricks.
Possibly, the PCB is powered with DC and the output is a FM or AM signal that rides on the DC.
Or maybe a Hartley (Split Coil) oscillator that draws more current as it approaches resonance.

I'm going to have to break out my big tinfoil hat and think about this one for a while.
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Old 01-18-2014, 08:56 PM   #19
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Default Re: Inductive Throttle Sensor

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Originally Posted by chriskent85 View Post
And it does have some little diodes in there and something u can turn but I had to use a torch and a small chizzle to get it apart. The whole inside is filled with that black stuff.
That is good information. That explains the strange resistance measurements and I bet it is a device that operates on the Hall Effect principle. I made some measurements today ACROSS a working ITC device with an oscilloscope. I will post this tomorrow. The resistance I measured earlier could be a guide to suspect the ITS as part of troubleshooting in a failed situation. Same resistance measurements posted earlier affirmed today. 39K ohm with a Simpson 260, 4.9Meg ohm across the ITS with A Fluke 79III digital meter.
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Old 01-19-2014, 09:39 AM   #20
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Default Re: Inductive Throttle Sensor

Here is some voltage measurements and wave form observations I made with an oscilloscope ACROSS the ITS (which is the same as pin 1 & 2 on the controller)

When pedal depressed the voltage rises to 13 volts DC. There is a .3 volt peak to peak pulse riding on the DC. This pulse width is 15 microseconds and a repetition time of 70 microseconds. The pulse width increases as the pedal is depressed further to 38 microseconds. The DC voltage changes about 1 volt when under load. The wave form is not jagged when observed closely. It is mostly a square wave with rounded edges on the rise, a slight slope down across the top of the pulse and a rounded edge on the trailing end. The repetition rate did not change when the pedal was pressed. A rate of 70 microseconds works out to 14.286 KHz.
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