diesel injector line speed pickup

[IceStationZebra]

I am trying to find a simple way to record the rpm of a diesel engine with my data acquisition system. Unfortunately many of the machines I am working on do not have pre-taped holes in the bellhousing to sense the ring gear. And I don't want to resorting to installing hall effect sensors, light sensors, etc. for time reasons.

I would like to use the sensors that measure fuel line expansion for use with a tach or timing light. (see link below for example)

http://www.avlditest.com/wEnglish/p...ducers/Klemmgeber_KG60_Englisch.pdf?navid=115

These are quick to install and I can buy the sensors for $60 each. But I'm not sure how to interface them to my data acquisition. I'm pretty sure they are piezo based, and I'm guessing that they are ICP because the cabling is nothing special. I have ICP cabability already.

Thanks in advance for any help. ISZ

 

[GregLocock]

Ask the distributor

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[IceStationZebra]

Tried that, they didn't want to give any info but were more than willing to sell me a $300+ widget that did a lot more than I really need.

ISZ

 

[MikeHalloran]

I have the impression that the line expansion type sensors basically have to be epoxied to an injector line in order to give a reliable signal.

Unless you're working on old engines, you can probably find a usable signal coming out of the engine's ECU. E.g. Deere ECUs I think send a 5V square wave at 30cycles/rev or so.






Mike Halloran
Pembroke Pines, FL, USA

 

[GregLocock]

Well, ask the manfacturer then. The distributor should be shot.

I've used an older version of these clamp on devices, which came with its own signal conditioning box, they aren't especially straightforward to use, with the occasional dropout etc.



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[WGJ]

Onosokki used to sell a tach that used a separate piezo sensor with a magnetic base, so that you could attach it to a cast iron head or block. The operator selected the number of cylinders and the box gave an rpm readout. Can't remember what the instrumentation o/p was, RS232? It was ten or so years ago.

Could try

http://www.onosokki.co.jp/English/hp_e/products/keisoku/automotive/ct6520.html

for a bit of research.

Bill

 

[Ron07663]

I believe some diesel tachometers use the alternator output to get RPM. You will need to correct for pulley ratio and pole number on alternator to determine exact speed from frequency.

 

[carnage1]

if it is sequential port or DI cant you just put a one shot timer on an injector line (as a signal filter) and read the resulting pulse train? you should get one pulse per 2 revolutions, the data system should be able to take it from there.

 

[IceStationZebra]

Mike - "I have the impression that the line expansion type sensors basically have to be epoxied to an injector line in order to give a reliable signal."
I hadn't heard of that before. I assume that if the clamping force is sufficient this wouldn't be necessary?

Ron - alternator output
I know that on one machine that had a light pick-up installed the output of the alternator is off by ~7%. This might be good enough for some of my tests but not others.

Carnage1 - That is what I am trying to do, but I want to know if I can hook up this type of sensor like an ICP accelerometer. I can condition the signal with my data acquisition system to take the 1 pulse/2 revs into account.

Thanks, ISZ

 

[carnage1]

I wasn't quite specific enough I mean use the one shot to read the voltage directly off the signal line that controls the injector thus eliminating the transducer. (or is there something fundamental I'm missing, my knowledge of diesels is purely theoretical, all my practical knowledge is gas engines)

 

[IceStationZebra]

At this point the engines have full mechanical injection. A mechanically injected diesel does not even need a battery/alternator if you use a manual fuel shut-off and air starter! BTW - The next generation of the engines we use will probably jump right to ECU's with a CAN bus which I can read.

ISZ

 

[Ron07663]

Re:alternator output
The frequency will be directly proportional to engine speed, unless of course, the alternator drive belt slips.

Any inacuracies you see are likley calibration errors in the tachometer head. If you monitor the frequency accurately, you should have little or no error.



Ron

 

[IceStationZebra]

The alternator error is due to belt slip, assumed pulley diameters, actual belt width, etc. The only way to determine the error is to compare the alternator signal to the actual engine speed first - but by the time I do that I might as well just leave the sensor installed.

ISZ

 

[not2fast]

Here's what i did for just that very purpose except it was for a timing light setup, but easily adapted to DAQ

I trimmed up a Piezo buzzer element from a buzzer and soldered this onto the Rod and then filed it down to size approx 4mm wide by 10mm long on the side of a small length of 6mm rod 20mm long and finished it off with heatshrink tube to insulate the assy and a made a small U shaped clamp to fix this against the Inj line.

The rest of it was a transistor amplifier that was used to trigger a MOSFET and a small coil (2 turns or so) of wire that used in series with a 50ohm resistor ... simply the MOSFET was creating a short circuit in the loop. 9V Batt > 50ohm R > MOSFET > 2T Coil > GND and the small signal from the Piezo element was triggering the FET.
Google for "measurement specialist Piezo film sensors Aug 98" there was a bunch of pdf's available. I dont have all the pdf's for this but you may find enough info in the above.

NOT2FAST