Inductive Throttle Sensor

[Knothead]

Originally Posted by radioman

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.

Ooohhhhh!!!! Now it makes perfectly good sense what it is!

NOT!!!

I'm glad all that info makes sense to SOME of you guys! I can usually make sense of mechanical stuff & even wiring on the electrical stuff, but when you start talking frequencies & pulse widths, you've lost me! I hope you can figure out what makes the ITS tick.....I can almost foresee the "homebrew ITS fix" panning out in front of me!

[radioman]

One goal of my postings is to be able to determine possibly if the ITS is good or bad by checking the resistance across it with an ohm meter, not so much how everything works. I searched everywhere and could not find anything about the ITS resistance.

[JohnnieB]

Originally Posted by radioman

One goal of my postings is to be able to determine possibly if the ITS is good or bad by checking the resistance across it with an ohm meter, not so much how everything works. I searched everywhere and could not find anything about the ITS resistance.

Since you have measured the resistance of two good ITS sensors with two different Ohmmeters and gotten the same results between ITS sensors, but an order of magnitude difference in the results between Ohmmeters, therefore using the Ohmic value as a Go/No-Go test might be possible at a local level, IF the same Ohmmeters were used, but not globally since the type of Ohmmeter used to measure the resistance will be an unknown.

Even at the local level, using the same Ohmmeter, using resistance to determine if the sensor is good or bad is iffy since we now know there is a compound circuit of some sort between the two wires attached to it.

I may be preaching to the choir, but different types of Ohmmeters give different readings on the same PN Junction. That is one of the reasons why the general rule of thumb Go/No-Go test for a semiconductor diode (single PN Junction) is a 10:1, or greater, front to back ratio rather than specific values. The circuit in the ITS sensor most likely has multiple PN Junctions connected in series/parallel, so resistance readings probably isn't a good yardstick.

As for how the thing works, we still don't know.

The ~1V variation in DC level is consistent with the pedal up/pedal down DC voltages used for troubleshooting an ITS sensor installed in a Series Drive (and DCS) cart. (See attached) The ripple seen on the DC is likely to be just that. The high current output to the motor is PWM and the duty cycle of the PWM varies with the throttle input to the controller. The controller/motor/cables is a huge EMI source, so every wire within several feet of them will have a similar ripple.

[radioman]

Originally Posted by JohnnieB

Since you have measured the resistance of two good ITS sensors with two different Ohmmeters and gotten the same results between ITS sensors, but an order of magnitude difference in the results between Ohmmeters, therefore using the Ohmic value as a Go/No-Go test might be possible at a local level, IF the same Ohmmeters were used, but not globally since the type of Ohmmeter used to measure the resistance will be an unknown.

Even at the local level, using the same Ohmmeter, using resistance to determine if the sensor is good or bad is iffy since we now know there is a compound circuit of some sort between the two wires attached to it.

I may be preaching to the choir, but different types of Ohmmeters give different readings on the same PN Junction. That is one of the reasons why the general rule of thumb Go/No-Go test for a semiconductor diode (single PN Junction) is a 10:1, or greater, front to back ratio rather than specific values. The circuit in the ITS sensor most likely has multiple PN Junctions connected in series/parallel, so resistance readings probably isn't a good yardstick.

As for how the thing works, we still don't know.

The ~1V variation in DC level is consistent with the pedal up/pedal down DC voltages used for troubleshooting an ITS sensor installed in a Series Drive (and DCS) cart. (See attached) The ripple seen on the DC is likely to be just that. The high current output to the motor is PWM and the duty cycle of the PWM varies with the throttle input to the controller. The controller/motor/cables is a huge EMI source, so every wire within several feet of them will have a similar ripple.

I agree with everything you post here. However I have used a Simpson 260 ohm meter to test transistor and diode junctions for leakage, opens and shorts for years. It would be interesting to take a resistance reading on a known defective ITS.

[JohnnieB]

Originally Posted by radioman

I agree with everything you post here. However I have used a Simpson 260 ohm meter to test transistor and diode junctions for leakage, opens and shorts for years. It would be interesting to take a resistance reading on a known defective ITS.

I wish I still had a 260, I think it is best analog multimeter ever made and I believe analog meters are better than DVMs for many things like checking for noisy pots and checking diodes and transistors, plus a bunch of other things where seeing the needle move is more meaningful to me than watching the digits change.

I agree it would be interesting to get resistance readings on bad ITS sensors, and there probably is some correlation between the resistance and whether it is good or not, but it'll take a good sized sample population to establish a pass/fail point, if there is one. We can troubleshoot an ITS sensor in a cart by the voltage readings, so there may be a way to bench test them by feeding in a DC voltage, inserting an iron slug and watching the reaction.

My interest in figuring out what the circuit hidden inside is, is just curiosity. Something I have been afflicted with as long as I can remember, which seems to be getting shorter these days.

[radioman]

I suspect the ITS we have been discussing is a self contained device powered from the controller that contains all the circuits to support the Hall Effect components to produce a DC output back to the controller depending of the position of the plunger inside the core. I suspect the circuit board image chriskent85 posted does all the processing. How they do it with only two connections, I haven't a clue.

[JohnnieB]

Whatever its is, however it works and the distribution of labor is intriguing since the same mechanical action produces different electrical results with different comtrollers.

TXT Series Drive.
B- to one side of sensor = 9.0V to 11.5V
B- to other side of sensor - Pedal pushed only until solenoid first clicks = 0.4V to 0.6V
B- to other side of sensor - Pedal pushed to floor = 1.5V to 1.7V
Variance and direction of signal between Zero throttle and WOT (Wide Open Throttle) = +1.1V

TXT PDS Drive.
B- to one side of sensor = 14.0V to 16.0V
B- to other side of sensor - Pedal pushed only until solenoid first clicks = 0.7V to 1.3V
B- to other side of sensor - Pedal pushed to floor = 2.5V to 3.3V
Variance and direction of signal between Zero throttle and WOT (Wide Open Throttle) = +1.9V

TXT Series or PDS Drive cart with Alltrax AXE or DCX aftermarket controller installed.
One side of sensor to other side of sensor - Pedal up = 10V
One side of sensor to other side of sensor - Pedal down = 6V
Variance and direction of signal between Zero throttle and WOT (Wide Open Throttle) = -4V

[simple man]

It would certainly be helpful to have a "go/no go" resistance value when going to a junkyard to get an ITS! I have one on my industrial cart that even though the potting material has cracked, works fine. I've had ones that looked physically perfect and were junk!
Yeah, I'm keeping an eye on this thread and want to thank you guys for doing all this work to find out what makes a little three letter piece tick!

[JohnnieB]

Originally Posted by simple man

It would certainly be helpful to have a "go/no go" resistance value when going to a junkyard to get an ITS! I have one on my industrial cart that even though the potting material has cracked, works fine. I've had ones that looked physically perfect and were junk!
Yeah, I'm keeping an eye on this thread and want to thank you guys for doing all this work to find out what makes a little three letter piece tick!

IIRC, didn't you put a brass sleeve in one and wasn't able to get the full throttle range?

I'm not sure is a Go/No-Go resistance value can be found, but I believe a "Bench-Test" might be possible.

We know the thing runs with an applied voltage from about 9V to about 16V from the voltage specs on the Series and PDS applications.
Perhaps a kluge with a 9V battery (or a small 12V Gel-Cell), a couple resistors and some clip leads might work.
Put a resistor (1K ?) in series with B+ and B- clip leads to the sensor and the voltage across each resistor and across the senor should change when an iron slug was inserted into the sensor.
If it doesn't, the ITS sensor is bad. If it does, it might be good.

Technically, doing this is roughly the same as using an Ohmmeter, but the voltage an Ohmmeter puts out (even an analog one) probably isn't enough to power up the PCB in the sensor assembly. However, if it was, inserting an iron slug ought to change the resistance reading on a good sensor.

------------
The only ITS sensor I have access to is the one in my cart and it is too darn cold in the garage for me to do anything other than shiver, so it will be going on spring before I can try it.

Another thing on my want to know list is what the B- to one side of the sensor voltage is and what B- to the other side of the sensor voltage is for Alltrax controllers with pedal up and pedal down, so a direct comparison can be made with the voltage specs for Curtis 1206, 1206SX and 1206MX controllers.

[azTony]

I have an ITS I could send to you JohnnieB if you want to do some tests. It was fine when I took it off the cart. I had a new one and went in to adjust the thing and figured while I was in there I would swap in the new one.