Tachometer Calibration with Multimeter
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- čas přidán 26. 09. 2019
- Here is a video for the car techs and enthusiasts to explain how to calibrate an check the accuracy of your tachometer. It does not matter what car, or year, or how many cylinders. The meter will give you the most accurate measurement you can get.
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The bigger the gauge the most horse power lol! Subscribed immediately
Great video and made it very simple to understand. Thank you
I made a typographical error in my original message. I put a 47 ohm resistor between the tach signal and ground. Gauge did not work prior to doing that. Now it works with the bounce when the RPMs change. I put the rectifier diode in line on the tach signal to help minimize the bounce. It appears to have made it worse.
The DC voltage coming off the negative side of the coil is about 14.3 volts while running. (Fluctuates some)
The ohms coming off the negative side of the coil bounces between 6,500 and 6,900 Hz.
I took these measurements off the the rear coil, not after the tachometer adapter if that matters.
The resistance from the signal wire to ground is 1.68 ohms.
I used the rear coil due to access. To get the readings from the front coil I have to remove the fuel tank and therefore can't start it. These are the parts that I used.
Thank you in advance for your help!
Doug
Biker's Choice Electronic Custom Mini Tachometer a.co/d/1TgOYjO
Baron Custom Accessories Tachometer Adapter BA-7315-50 a.co/d/84HkQdr
20PCS 1N4005 Rectifier Diode 1A 600V DO-41 (DO-204AL) Axial 4005 1 Amp 600 Volt a.co/d/0PYQJeo
PARTS EXPRESS 47K Ohm 1W Flameproof Resistor 10 Pcs. a.co/d/7C6n0Qz
Clear and concise explanation, thanks so much. Came in handy when I was tuning the carb and governor on a neighbor's lawnmower (RPM was too high during idle and under load).
Excellent explanation! Applied great math skills, theory and how to use multimeter.
Thank you very much!
too much information under 17 mints. good work bro. thumbs up
This is also very helpful for figuring out the rpm on a small engine without having to purchase a cheap, Chinese, inconsistent tachometer from Amazon.
Excellent video. Top guy. Subscribed.
This was great. The clamp is called induction. Almost like a current transformer. It’s 360 times two revolution equals 720 degrees, two revolutions to make one revolution on a four stroke. One thing to mention is you can’t transform DC. That is why the old points would open (now it’s done electronically) to transform from coil primary to secondary, to fire the plugs.
In the terms of this video the inductive pickup is a clamp similar to a Hall effect sensor but is powered and reacts similar to a FET without a gate saturation from direct connection. That’s why I mention it. Toroid induction is not a thing in DC and that’s why the coils are HVDC discharge, happens in joules, not volts on the design level. Not sure if you’re trying to repeat my whole video but it’s already obvious to me how the engine works.
Excellent presentation. Sure helped me! Thanks.
You have a teaching talent.
appreciate you taking your time and showing use some valuable info that probably a lot of people doesn't want use to know. thanks again very valuable info.by watching and learning your knowledge makes some of use look really intelligent when it comes to electronics
I appreciate it. Just trying to become a real CZcams channel by a useful means. As much as the old crew doesn’t think so, I find it to be a viable career path that doesn’t politically dictate if you are “allowed” to be a professor. Hopefully with enough likes and subscribers, this path I’m taking actually grows into something.
A very clear explaination . Thanks .
Brilliant video! Very well instructed. :))
Great really clear finally I understand....
Very informative and explained great
Very informative, but if you working on a "waste spark" ignition systems you dont need to multiply by 2. For example mazda and ford vehicles with 2 ignition coils for 4 cylinders🙂. Like mazda protege. They have ignition systems like 2 stroke engines
This guy is awesome 👏🏻
Very informative and clear
Thanks Bro That was So Informative Just what I was Looking fpr
Right on dude. Good video
Awesome explanation, Rob! However, I have a puzzle for you. 🙂
My level of expertise is as follows:
40+ years auto mechanic
24+ years journeyman toolmaker & cnc programmer
17 years mechanical engineering/machine design
45 years and change taking shit apart to see how it works, and then either making it better, or destroying it for spare parts. Haha
I have an old Sunpro CP7909 tach that I'm trying to get to work on my 2006 Polaris Ranger 500, carburated, single-cylinder SxS. The tach has three settings for 4, 6, & 8 cylinders, and thru-hole resistors soldered on the pcb in-line with each switch setting....as well as a small surface mounted potentiometer for fine tuning.
The approximate resistor values for each setting are as follows:
8 cyl - 196kΩ
6 cyl - 260kΩ
4 cyl - 382kΩ
Using those numbers as a baseline for my math, and reading online that the IC chip in the tach takes a pulse reading in relation to the resistance of its control pin, I figured that swapping out the 8 cyl. resistor for one that was roughly 1.528mΩ should make it work on my single-cylinder engine. However, it did not, and the tach just ran up past 8k and kept going before I unhooked it so as not to let out any of the magic smoke.
Do you know if I did this correctly? Is there another way or something that I'm missing?
Also, this is one of my main sources of "this can be done" info after reading almost everywhere that "it isn't possible". www.instructables.com/Automobile-Tachometer-on-an-outboard/
I freaking hate people who say that there's ANYTHING that can't be done. *eye roll*
Thanks for your attention to detail, Brother! You ROCK!
-Joshua
You did the right math, but on the wrong parameter. Older tachs ran on pulses like if you were to tap the gas pedal 10 times per second vs 1 time per second. The resistance is only for input pulse amplitude, not the number of cylinders. There is a bunch of math to describe time constants for capacitors and line control signal resistance but I’ll omit that for now. If your math was correct it would be a 3ohm because the tach is pulling a 2 cylinder firing count at any time. The Pulse Width, not the Pulse Count, is what you have to measure. That will be in milliseconds value of on-time. The wattage the meter sees is a combo of amps and volts. That’s why the resistor AND the capacitor changes. The cap is changed by the IC and the resistor by the switch which changes the time constant and power to the magnetic pendulum in the tach needle. Need to know the pulse width of your input on the new engine
I’m making a signals video today that may help you
@@sinewavespecialties2373
Thanks for your detailed response, Rob.
So, if I am understanding this correctly, then I'm going to need to bust out my scopemeter and measure the pulse width to be able to make the correct circuit modifications?
Oh, and an update on this since I posted last (sorry for the delay as I was busy with family stuff for Independence Day). Upon more in-depth circuit tracing, I noticed that the resistors for each setting have their respective trailing leads soldered into a common buss, and are therefore backtracking to create different parallel R values to the IC depending on the switch position. Ugh. Lol.
I'm not a full-on EE or anything, but I'm trying to get there. I think it would be best if I just sketched out the circuit and posted pictures of what I have, if you wouldn't mind having a look. It's going to take me a little bit to get that done as this isn't as imperative a project as many of my others at the moment, but I will do it. Also, in a huge bonehead move, I tried to save a few bucks last year when replacing the battery in my Fluke 199c Scopemeter by buying an aftermarket one from Amazon. HUGE MISTAKE! I have found the resistor that it fried in the charge circuit, but just haven't gotten around to fixing it yet as I don't need the thing very often. I'm just hoping that the resistor took the brunt of the spike and that there wasn't any damage to the PCB anywhere else, and that it's not just a very expensive yellow brick now. 🤦♂️
I'm keeping an eye out for that new video you mentioned, and looking forward to learning more! Keep in touch.
-Joshua
@@joshuasparks6563 I’ll have it finished up today and some specific methods to analyze. I got my first scope literally two weeks ago but it’s my translator for everything now. MSO5104 and bought the waveform generator. I plan to put a PWM signal to the tach I have on a ramp function to see when it starts moving with the variables being width, voltage, and frequency. One of them should give me something. Will have to bust out PNP and NPN MOSFETs if it’s an AC signal like most of the tach signals in cars. Be advised, my large scale automation tower is going to be complete AFTER I get the baseboard which is on backorder and projected to ship 9/30. Sucks. It’ll be a full blown 36” tall 6” deep 24” wide tower assembly for experimentation
Thank you. Very useful.
Thanks Rob!
Great video Rob. Would this process work on a Mazda Rotary engine? Thanks
Great video
I have a 1965 Ford Mustang with a 289 V8 and have used a gear ratio app to compare the tacho reading at different speeds and after lots of issue getting a good reading a 400v 1A Diode fixed the issue in line at the coil side to the tacho, I have confirmed the Tacho is out by 400 rpm at 100 km, I have been told I can fine tune it with an adjuster screw on the back but I what be able to do it with a second device like a multimeter to correctly adjust the tacho.
Would the formula HZx2x60 be the same for my 1965 Ford Mustang V8 using factory coil, the green wire from the tacho goes to the negative side of the coil, what is the correct formula .
Also on a cheaper multimeter would the HZ symbol be V~
you nailed it... thanks
I picked up a cheap signal generator to calibrate tachometers out of the car. It would be nice to have a chart of the output HZ setting to create a certain RPM reading on the tach, with certain number of cylinders. Maybe a 4 cyl, a 6 cyl and an 8 cyl. at 2000, 4000 and 6000 RPM. etc. I am looking forward to the next videos.
The boat ones I just started will likely be in the range of 10-15 videos long. I’ll see if I can sneak an experimental video in there for a signal identification and propagation one that explains what these tachs are usually looking for
Thanks for the video! I put my multimeter on the negative coil (same as green wire on my aftermarket automotive tachometer) since my car does not have separate coil packs. It's a 6-cylinder. The meter shows about 250 hertz at 800 RPM, which calculates to (200 x 2 x 60) / 6 which should be 4000 RPM. My meter shows 6000 hertz at 1600 RPM, which calculates to (6000 x 2 x 60) /6, which is 120000 RPM. Do you know what I might be doing wrong?
Thank you bro
cool bro!
thanks it helps a lot
Very nice and informative video. Wishing you could do videos with a Deisel engine whose rpm sensor is attached to the injection pump. Thanks in advance =)
Ill put one up. PNP or NPN op amps are pretty good with stuff like that without interrupting electronic signal quality. Let me see what I can put together on that one.
Thank you Rob. Good job. I have a brand new faria tach for my 350 chev marine engine. Just put a new motor in it and it does not appear to be recording the correct RPM. The mechanic figures thretach might be out of wack. Ant tips on these tachs or same as any other tach.
Jim
I am actually putting together a video series, even though i say that and never seem to, its actually going to happen now on a much more productive level. I have spent $3500 on a PLC stack up and will be doing videos on how they work and what they can be applied to for boats and vehicles. It will be a wild turn for the standards typical to the industry but much much more powerful
Great video! I’m doing an engine swap to an MR2. I haven’t installed the engine yet but just wondering about the tach. The MR2 tach has resistors, but I’m not sure what resistor to use so that it reads to the RPM signal from the coil packs off the Honda k24a2 engine. Based off your video I can determine rpm from the Hz reading. But how can I use that information to change the resistor sensors so that the tach reads correctly? The old MR2 engine read from a distributor cap. I’ll be running a haltech ECU and the software should be able to read the RPM as well. I’m just not sure how I can get the RPM signal to read on the tach.
Most systems that read into a tach signal have two things inside; diode and timer/counter. Most tachometers need very little input to read a signal and the resistor isnt there to identify the signal, its there to keep the input from burning up the tachometer. Get a 20k, 15k, and 10k resistor and start with the 20 then 15 then 10. You can confirm the correct one with the procedure in the video that it is reading correctly. In very rare cases a capacitor is needed with the pull resistor but its not often at all.
typically a tach with a resistor has a capacitor and an analog range inside it for a certain number of millivolts or milliamps to sweep the gauge. So in my experience, and soon to be yours from the next couple videos, i would start with a 15kohm resistor and step it down 2000ohm at a time until it reads right. Most hall effect, current reads, inductive and capacitive sensors seem to read well at 10kohm signaling however for vehicles it may be different use the meter as you try different ones and confirm the right resistor is what I'd do if it was my vehicle.
So on a evinrude 225hp etec 2stroke I multiply Hzx60 correct
I watched your video and I still have some specific questions I was hoping you could help me with. I have a Honda VTX 1800 motorcycle. It's a V-Twin with two separate coils. Some bikes have a wasted spark where it ignites on the compression stroke and the exhaust stroke. This one alternates back and forth only on the compression stroke. I purchased an adapter for the lack of better term that takes the negative signal from each coil and discharges it through a wire to the tachometer. Once connected properly it did not work. I read in the comments from someone who purchased the same device that a 10K resistor needed to go from the tachometer wire to ground. I did that and the gauge began to work but it had needle bounce. Cruising at a steady speed it would be okay but accelerating or decelerating it would bounce. I then read online that if I installed a 1N4005 (1A 600V) diode in line to the RPM gauge it would correct the bounce. It actually made it worse. I'm desperate for some help. I can send you a link to the gauge I purchased and the electronic device that gets installed in line. I can't find anybody with the knowledge that you have. Please help.
IF, and I stress IF, the signal from the coil discharge trigger negative is the proper place for the tach signal to be acquired, 10kOhm is either too much resistance OR when you hooked it up without the resistor it caused a problem in the gauge. What I personally would do is power up the gauge and start the bike with the two disconnected from each other and set the multimeter to DC frequency (Hz) and get two things; voltage and frequency. USUALLY, not promising, the tach reads from a 5VDC signal on pulse inputs. Now measure the resistance of the signal wire on the tach to chassis ground. When you have those THREE values, post them here. You need a corrected voltage drop is probably the issue. An internal failure of the gauge may require a capacitor in parallel to smooth it like an anti slosh module usually found on older clusters, newer cars just use averaging to smooth out needle flyback
@@sinewavespecialties2373 I was wondering if you would be able to help me with this tach problem. I have the VTX disassembled ready for your suggested modifications.
Does min/max with the clip on style lead just give you the max Hz or a different formula needed?
min max is the respective minimum or maximum of the reading. works for hz, amps, volts, etc. If you want to see how low the cam runs then minimum, if you want to float the valves use maximum.
I’m trying to find max rpm on a 2stroke outboard boat motor using a induction clamp. Min/max doesn’t work on my Hz setting. It is also reading crazy high Hz like 150 witch would be 9,000rpm if I’m correct. I don’t think that is accurate. Any suggestions?
Would you only test the negative wire on a single coil? And how do you actually change the tach to match the readings?
you only have to know the firing frequency which will be unaffected by polarity since you only need to read a state change such as energized or not energized. Changing the tach to read a specific system is a video that will come out soon as it will be a full blown series on automation controllers. Currently putting an Industrial Automation system into a 3500 Savana Long Chassis for demo
How does this work for diesel engines?
Can this be done on a diesel and would the w terminal on the alternator give the reading cheers.
The meter will generate a reading on an electrical pulse input, so this means something that gives off a signal for every rotation or every other rotation of the engine would produce a reading that can be mathematically applied using this video, HOWEVER, if using the alternator you could get a reading from the rectified 3 phase or the actual 3 phase but now you must figure out belt length and ratio of the crank to the alternator to know what the ratio of revolutions there are, it begins to get a bit tricky but my next (long awaited) video will describe that
I wanted to ask is it posibel engine run ON because of tacho gages?
Some where in wikipedia is mentioned tacho generator so is that thing pulse generator?
What hapens if you swap those wiering?
I cinde of geting back charge from me alternator that thing is externaly excited and has no center tap its delco remy alternator from france and I have singel hei E core type ignition coil so where do I wire me tachometer to???
You are reading the actual spark lead or wherever the pulse origin is. If you read from the entire engine trigger, you will have to divide the final value by the quantity of cylinders
@@sinewavespecialties2373 ok I understand. But I have another problem I actualy have build in destributor 4 pin gm ignition module aperantly that thing is polarity sensitive and I do have positive linear voltage regulator inside me dashboard I did try to use that delco starter motor selenoid to bypass some voltage because of winter time I do have problems starting me car.
But when I try to use that R terminal on starter selenoid me fuse pops?
Any ideas how can I bypass this problem?
I recently have also some unusual problem apwrantly me car refuse to shut off when all 4 blinker works I can not detect the problem why this acured .
I did swap out back lights from new'r model year car but terminals pins and bulbs are the same I even swaped out 3 relays who are 3 wire blinker relays they do all cinde of strange things but not show the right direction some times all 4 light come on brake light blinker light realy strange things going on with me car.
That relay staff nearly resembels hit and miss engine ignition cinde of.
So I wondered If I culd use relays as triger instead of that gm ignition module because its polarity sensitive.
So I do have more of those starter selenoids wuld it work If I wound 2 selenoids in series ore pararell to bypass voltage to coil?
It is anoying GM product to be exactly Opel Ascona C ore Camira with 1.3 L sohc engine that thing drives me nuts .
I cant realy finde any info on the internet related to such strange behaviore.
I must admit I was impresed that the car actualy works in union with the relay so that brought me to thinking can It be controled?
With cinde of oscilation circuet ?
Me engine does have bade tendency to run at around 500-600 rpm I like the fuel economy .
So does there any way exist how I can bypass those problems?
How should I trnslate my hertz reading on my main coil wire if I have. Single coil on a in-line six motor? I have 120Hz reading and don’t know what to do with it :)
You need to know how many cylinders are firing per revolution and you’ll be able to calculate anything else from that number. SOMETIMES, they are different for specialized or non-consumer engines. I want this video to be all comprehensive rather than only automotive based. Treat two cylinders firing at the same time as a ONE in the math.
I may make a follow up video on this topic, I have 4 more videos uploaded for scheduled dates currently but this one has gotten a lot of attention and questions
So on harley Davidson motorcycle it would be Hz*60= RPM? 4 stroke 2 cylinder
Same math on a Harley as all other 4 strokes
Is it possible to calibrate a 4 stroke tacho to work correctly when hooked up to a 2 stroke ?
negative sir, as the tachometer would have to ignore half of the inputs, if you set up transistors to switch on and off for each pule input it would work, but that's a largely useless endeavor unless the tach you want to use is really really really that important
@@sinewavespecialties2373 Thanks, yeah the tacho is pretty important as I'm using it on my motorcycle, its a 1997 Yamaha 2 stroke single cylinder road bike. What kind of transistors do you recommend ? I tried using a frequency divider by 2, the IC7474 but that didn't work and made the tacho go wonky and wierd. I guess it couldnt work at such high speeds. As my bike doesnt have a tacho out from the factory, I plugged the source wire of the tacho, to the spark's pulse wire, voltage is a very gentle 3-5v and it works fine, but not correctly. Thanks.
@@BrattyBiker that divider probably is fine, issue is probably reactive power input, circuit probably needs an inductor in the mix somewhere to stabilize the power if it isnt AC
@@sinewavespecialties2373 Thanks. Yes, the tacho works at 12v DC. The IC7474 works at 6v DC so I plugged it in the lighting coil which is 12v AC and used a IN4004 diode to convert it to a 6v DC. Unfortunately I still blew the IC up within seconds but the diode was working fine, I tested resistance too. This seems to also have messed up my tachometer now that the needle doesn't move beyond 2,000RPM 🤦🏻♂️
2 wire Inductive clamp, one around spark plug wire and other to ground, is that correct?
Your inductive pickup is going to act as a “positive” source so yes,
@@sinewavespecialties2373 Can you explain how you bench test a tach. I think it works in reverse, send a variable pulse to the signal wire and ground from the pulse generator?
@@robertmccully2792 I have not bench tested one, just comparative test in same source. If I understand tachs competently I’d say only an analog drive tach can work in reverse and even that is a “maybe”. Issue with digital is it is using absolute values for its function. Most analogs I would guess have a diode to produce the same resultant output so the needle doesn’t go haywire. NOW IF you blow that diode in the system, which I’m sure is shared by a bunch of gauges to save money, then yes, I believe it could fly the wrong direction. This is all theory, so hopefully something I said helps
@@sinewavespecialties2373 yeah my hour/ tach meter from Amazon had some very basic install instructions. Mine is two wire induction style, but instructions just state WRAP WIRE FIVE TIMES AROUND THE PLUG WIRE. I agree with you guys, the main wire needs stripped back, exposing the two finer wires, determine which is the pickup, determine which is ground. Then move forward with installation. (Damn Chinese Amazon electronics literature) 🤦
@@sidewayzmike pretty typical, its the same with key fob simulators used in VW and Audi vehicles for remote start systems. Have to wrap the fob because the NFC isn't mainstream yet for programming to a module.
If a car have 3 cylinders than Hz x 3 x 60 am i right?
I think most of cars like as i have Suzuki Swift 1.0 G10A engine 3 cylinder piston strikes up and down motion ate not in same 2 up single down 1 up and 1 down it can be any pattern
It doesn’t need to be because the crankshaft rotation has the same ratio with respect to all other pistons in the engine.
So I have a v6 with a coil pack, where would I connect the lead in my case?
The coil pack will have a trigger wire that will provide a digital pulse signal that is read capable with a multimeter in the DC Hz function. Just need to test to know which wire.
If you are measuring from the negative of the coil, the coil is sparking 4 times for each cylinder, each of which has 2 revolutions per spark. So wouldn't you then want to divide your result by 4?
Are you reading it will a scope or meter? Meter will not catch 4 sparks per cylinder. ICE's do not spark more than once. If a scope is seeing 4, it is due to residual discharge. Is this a newer vehicle or a race vehicle?
@@sinewavespecialties2373 I'm working on an old Mercruiser 3.0L boat engine.. essentially a repurposed GM engine from 1990. I bought an Actron automotive multimeter with an RPM feature and it reads double what my RPMs are.
@@barry.anderberg put a diode in line with signal wire. Most tach signals are AC sine wave, if the signal goes away entirely, try flipping it and seeing if that helps. If it reads the same then your tach needs to be setup/programmed.
Name of that multimeter u using
Fluke 289 sir. The $650ish process meter with the IR port on top.
www.fluke.com/en-us/product/electrical-testing/digital-multimeters/fluke-289
Wish u did an actual reading on a car. Makes it more clear
Ya know, I think I could do that for ya. There has been a TON of response to either I'm wrong, it was great, what about xxxxx tachometer, maybe this needs an electrical explanation rather than a mathematical one. Thanks for the input.
I have 3 different multimeters they each read different hz, one is wildly different.
What meters do you have? Brand and Model?
Does anyone know how to convert a tachometer to a speedometer?
Why would you do that instead of using a speedometer?
Make it simple. RPM = Hz*120
I would but that defeats the purpose. Simplicity in explanation of an unknown concept to people only makes simple people. This channel isn't to simplify anything. Also one equation does not suffice for multiple stroke types.