Multimeters and test equipment.

[mudnut]

G'day, all. I have spent many hours trying to get details on test equipment that is accurate and affordable. I have came up with this gem;
http://www.ebay.com.au/itm/Brand-New-Digital-Multimeters-Scopemeter-Oscilloscope-UT81B-Multimeter-EMH051-/171201619502#vi-content. This is for gauge cluster testing and reconditioning, hopefully.

I have two doubts about it. 1) It comes without leads, case etc. (there is one from Hong Kong withall the goodies, but 1-2 months delivery.
2) I have never bought anything from Amazon.

I have tried to source equipment from the local electronics store (Jaycar outlet), because I like to shop locally, but they have less able equipment at way higher prices.

If anyone knows of viable alternatives, your input is welcome. Thank you. mudnut.

[TPC]

It does seem to be a very clever meter, especially for that price, I don't believe you will get anything locally for any ware near $200.
I understand your hesitation buying it from ebay as this type of seller can be difficult to deal with when you receive a faulty unit and I would not believe the unit is in Brisbane as the add states.
I have a Fluke 287 Multimeter myself, that cost about $650 and does not have an oscilloscope.

[NP99]

Amazons are excellent to deal with. Some items they won't post to Australia.

[MudRunnerTD]

Yeah I would not hesitate to buy from Amazon. Too easy.

[mudnut]

This one in the Jaycar catalogue http://www.jaycar.com.au/productView.asp?ID=QM1577&CATID=97&form=CAT2&SUBCATID=1062#1 looks like a pretty good unit, but does not measure micro amps.

And this one looks like a sturdier unit, but then again is something goes wrong, that's a lot of cash down the drain

http://www.ebay.com.au/itm/USB-HandHeld-Scopemeter-Oscilloscope-DMM-3-5-UTD1025CL-200MS-s-Multimeter-/121072540328?_trksid=p2054897.l4275

[threedogs]

3kg regular post parcels are $14.50 approx. and a bit more for 3kg express post.
5kg express post cost around $20

[BillsGU]

This one in the Jaycar catalogue http://www.jaycar.com.au/productView.asp?ID=QM1577&CATID=97&form=CAT2&SUBCATID=1062#1 looks like a pretty good unit, but does not measure micro amps.

And this one looks like a sturdier unit, but then again is something goes wrong, that's a lot of cash down the drain

http://www.ebay.com.au/itm/USB-HandHeld-Scopemeter-Oscilloscope-DMM-3-5-UTD1025CL-200MS-s-Multimeter-/121072540328?_trksid=p2054897.l4275 (http://rover.ebay.com/rover/1/705-53470-19255-0/1?campid=5336709507&toolid=10001&mpre=http%3A%2F%2Fwww.ebay.com.au%2Fitm%2FUSB-HandHeld-Scopemeter-Oscilloscope-DMM-3-5-UTD1025CL-200MS-s-Multimeter-%2F121072540328%3F_trksid%3Dp2054897.l4275)

Of the three this one from China looks the best as far as specs go. It has a real CRO probe output for a start. The USB output should enable you to view the screen on a monitor or a laptop, which is a great help when looking at complex waveforms or pulses. Ask if the software is included.

[the evil twin]

Of the three this one from China looks the best as far as specs go. It has a real CRO probe output for a start. The USB output should enable you to view the screen on a monitor or a laptop, which is a great help when looking at complex waveforms or pulses. Ask if the software is included.

I agree.
I haven't had anything to do with that range of Uni-T gear but their DMM's are OK.
There is any amount of the UT1025's for sale out of the U.S. if the OP doesn't want to deal with China as well.

[P4trol]

Never tried these brands. If it is Chinese and on eBay, chances are you can get it cheaper.

http://www.aliexpress.com/item/Uni-T-UT81B-SCOPEMETER-MULTIMETER-OSCILLOSCOPE-USB/325618133.html

$142 isn't too much of a gamble. Shipping time would be the downside.

[mudnut]

Thanks for your opinions, blokes. The uni-t unit does look tempting, so I will keep searching.

[lhurley]

Not sure what your specific needs, but I got a decent multimeter for like $35 from jaycar. It does everything I need it for.

[MudRunnerTD]

Not sure what your specific needs, but I got a decent multimeter for like $35 from jaycar. It does everything I need it for.

Yep me too. I has a variable control rather than a manual select option and i like it. Mudnut i only use mine to measure 12v and Ohms on occasion and that is only looking for continuity. ET is talking another language to me and i simply have No Idea what he said ;) and Bill was border line for me ;) You must be playing with other stuff yeah? do you need the sinewave meter etc?? If so then spend the large for sure.

I dont think i helped......... :p

[the evil twin]

ROFL... My bad... I'll try and translate.
The OP is interested in potentially refurbishing instrument clusters so he is after waveform and signal pulse measurements and also very very low current applications.
An everyday Digital Multi-Meter (DMM) won't do all those jobs but the hand held Scope Meters will suit admirably so he only needs one bit of kit for most of his testing.

[mudnut]

The Jaycar qm1551 measure micro amps and I can source it locally. That and a mini handheld oscilloscope for $80 and I have the tools to do the job but accuracy could be a problem. Signal generators are really expensive for what they do, but I haven't fully researched them yet.

[the evil twin]

Yep, agree... it is your budget and your cash and that will get you started. You can always buy better gear later if it is worthwhile

For a sig genny you could use one of the el cheapo kits ex Jaycar.
You won't need a full on sig gen because you can look at and adjust the output waveform of a kit sig gen with the Scope Meter or Cro.
A saw tooth which is the easiest therefore cheapest waveform to generate will work just as good as sq wave, pulse or pulse width modulated for testing vehicle instrument clusters 99% of the time.

[BillsGU]

Yep, agree... it is your budget and your cash and that will get you started. You can always buy better gear later if it is worthwhile

For a sig genny you could use one of the el cheapo kits ex Jaycar.
You won't need a full on sig gen because you can look at and adjust the output waveform of a kit sig gen with the Scope Meter or Cro.
A saw tooth which is the easiest therefore cheapest waveform to generate will work just as good as sq wave, pulse or pulse width modulated for testing vehicle instrument clusters 99% of the time.

I agree. Also your sig gen will only need to generate low frequencies. Most of your work will be below 100 kHz which electronically is considered to be in the audio range. For this reason an average scope will do the job. It does not need a large frequency response. As ET says, don't go overboard just yet. Buy the basics and build up on that as / if required.

[mudnut]

I was reading the specs on some of the sites for the uni-t and some don't list the micro amps as such, but as 400mA and 4000mA.

Just for a start, so as not to part out a lot of cash, I have taken the speed sender from my cactus gear box and will set it up with a small stand and flex drive to fit the variable speed battery drill. That should suffice for an accurate speed signal. I might try to get a distributor and set that up as well.

Is the green/red wire from the TB42E speedometer to ECM (ECCS module), pin a feedback signal for something, or an input to the speedo?

[BillsGU]

I was reading the specs on some of the sites for the uni-t and some don't list the micro amps as such, but as 400mA and 4000mA.

If it was me I would want it to measure micro amps. 1 milli amp is 1000 micro amps. When you are fault finding and aligning low power circuits you need to be able to measure low currents. Some years ago they bought new multimeters at work. They sent an electrician out to select and buy them and when they were delivered they were useless to the electronic techs because of their current range - they couldn't accurately measure low enough.

[mudnut]

It just makes me nervous buying stuff off people that can't list the product specs properly.

[P4trol]

But when you are dealing with model numbers you just check the specs out elsewhere, and buy with the cheapest seller you reckon will deliver the goods.

You're not buying the cheapest price due to their product knowledge and extensive product listing. You did that work. Discount for you.

[mudnut]

Today I checked my battery charger/ 18 amp booster output with four meters connected.

The inbuilt voltmeter indicated (MC) 14.9.

My Kingdom ETU multimeter (MC) 15v.

My Optilux (Auto specific) Multimeter (MC), 13.8

El-cheapo E06100 digital multimeter 13.11 volts.

Getting accurate base readings is going to be a problem.

[mudnut]

My "toy" oscilloscope turned up today. It has slightly different characteristics to the online instruction manuals,and the interpretations from Chinese don't quite match either, but I'm slowly working it out. It has data saving and uploading to PC capabilities and a test output signal somewhere as well. I checked out a few different outputs from phone chargers and DC power supplies and got good results. If you listen closely you will hear me banging my head and tearing out my hair as I learn to use this nifty little device. Speedo sender signal output pics to follow...hopefully.

[TPC]

Today I checked my battery charger/ 18 amp booster output with four meters connected.

The inbuilt voltmeter indicated (MC) 14.9.

My Kingdom ETU multimeter (MC) 15v.

My Optilux (Auto specific) Multimeter (MC), 13.8

El-cheapo E06100 digital multimeter 13.11 volts.

Getting accurate base readings is going to be a problem.
That is a hell of a variation.

[mudnut]

The Jaycar multimeter has turned up at the shop. Can't wait to get into town and pick it up. It will be interesting to see what it reads too.

[threedogs]

If you see something you want in the states and they don't post to Aust.
Try gateway.com .they will supply an American address and resend it to you for a very small fee.
OD put me onto them

[mudnut]

The Jaycar QM1551 is shaping up to be a very handy piece of gear. It even has an inbuilt, non contact AC voltage detector light and a temp sensor.

[TPC]

The Jaycar QM1551 is shaping up to be a very handy piece of gear. It even has an inbuilt, non contact AC voltage detector light and a temp sensor.
Have you compared the DC voltage reading to the others yet?

[the evil twin]

Today I checked my battery charger/ 18 amp booster output with four meters connected.

The inbuilt voltmeter indicated (MC) 14.9.

My Kingdom ETU multimeter (MC) 15v.

My Optilux (Auto specific) Multimeter (MC), 13.8

El-cheapo E06100 digital multimeter 13.11 volts.

Getting accurate base readings is going to be a problem.

Doesn;t suprise me too much... 'cept maybe the last reading.

Not many battery chargers output true DC so the waveform could be noisy as hell even across a Battery which is in effect a dirty great big filter capacitor.

A difference of maybe a quarter volt would not be unusual on reasonable meters (not high end like Fluke etc) and throw in some elcheapo's and they variations could be way more

[mudnut]

This is the AC output of the speedo sender at about 57kmh which shows around 174 to 178 Hz. (But I may have read that wrong)

I am still learning the scale and accuracy of the screen.

[P4trol]

Here's a similar looking one I found tonight.


http://www.adafruit.com/products/468

[mudnut]

The readings are a little better tonight, for some weird reason.

Qm 1551 is at 12.58 volts

El cheapo digital is at 12.51 volts (new battery)

Power supply in built (moving coil) 14.8

Kingdom (moving coil) just over 12 volts.

Optilux (moving coil) is at 12.2 volts

[mudnut]

This is the link to the instruction manual for the oscilloscope: http://www.wakamatsu-net.com/biz/EGO_DSOManual.pdf. Its the only thing I can find, so far and it has a slightly different display.

[BillsGU]

This is the link to the instruction manual for the oscilloscope: http://www.wakamatsu-net.com/biz/EGO_DSOManual.pdf. Its the only thing I can find, so far and it has a slightly different display.

Not so easy to understand! Would be better with the instrument in front of you while you are reading through the instructions. Odd that it doesn't have AC coupling. It would be difficult to get an accurate peak to peak reading if the waveform has a DC bias. It will just take some getting used to.

[mudnut]

You would think that, but the display is slightly different and the designations aren't the same letters, in the right order or even colour.

I have made a set of test leads which make it simple to measure the tacho signal across the resistor which is inline between the coil and gauge. It is a 1-1.8 volt square wave but is very noisy, with spikes created by the current collapsing in the high voltage side of the coil.

The oscilloscope reads the AC signal from the speedo. It is just a matter or adjusting the Y offset to the centre of the grid. When connected to the 12 volt power supply, it also reads the pre-rectified signal as AC too, so I don't know why they reckon it is Only DC coupling. After working my way through all of the menus I have found measurements for V peak to peak, V rms, and V average, so forth.

I have also worked out how to set up the inbuilt Test Signal output. I can get it to closely resemble the Tacho signal, so I will try to get the tacho going too. With all the variables present in the circuits, I think a good frequency counter and function generator would be a good investment, If I decide to keep doing the clusters.

[mudnut]

This is what I have found, so far in car and on the test bench. On the bench, I tried connecting a variable resistor grid across the tacho input and earth. With the Oscilloscope Test Signal 1.3 Volt square wave imposed across a 2.2 k resistor, but the tacho didn't move. I will have to get a function generator capable of producing a 9V bias. I might also have to tie the voltage to the 12v positive with another high value variable resistor.

[mudnut]

I have found that the QM 1551 cannot read square wave duty cycles correctly. I will have to take it back and get another one sent out as getting the correct signal for a tacho will be essential to produce accurate readings.

[mudnut]

The new multimeter turned up at the shop today. I took my meter in and hooked it, and the replacement up to oscilloscope test signal for the shop assistant. My meter was flickering up and down within in 3 to 5 Hz and the new one was steady as a rock. The shop assistant took the defective one and gave me the new meter, no worries. At home I have re-run some tests and am more impressed with the Jaycar QM1551. I thoroughly recommend it to anyone as an excellent and versatile tool.

[mudnut]

R.I.P. the handheld oscilloscope, my bad.



I have been researching a replacement. I had a brain fart and bought an Allsun EM125 which is useless.

I am a bit averse to buying online, but I found this beast:

http://www.ebay.com/itm/HANTEK-Portable-DSO8060-60MHz-Five-in-one-Handheld-Oscilloscope-Spectrum-genera-/290672129924

Has anyone dealt with Hantek equipment at all?

[GeeYou8]

If you believe the specs the Hantek looks good, I have only just read this thread so I don't know what level of tech you are looking for.
I do know that Fluke multimeters give more stable & accurate measurements & they are reliable (still work after being dropped), they are what I would recommend to a customer, but are expensive for hobby use.
I am a bit spoilt when it comes to test equipment, 35 years in an avionics/instrument/calibration workshop.
Graham

[mudnut]

I used to have Fluke meters at work, but the price is prohibitive for what I need. I was hoping someone had bought Hantek gear, and could tell me if the software was stable and reliable.

[mudnut]

I bought an Allsun EM125 scopemeter, as it looked like a unit that was rugged, and repairable. Last night the on button failed. It is just out of the 30 day return window, so I had a go at repairing the switch.

The switch was easy to disassemble, but one of the contacts was showing signs of having been hot. The contact was so lightly built, that no matter what I tried I couldn't repair it.

I can't understand the manufacturers thinking when they put this thing together.

The rest of the internals are really well put together and they have even used spring washers on the screws that
join to earth. Why put together something so complicated and hard to engineer, then use a crappy switch?

Any way, I ended up using a switch off a Sony Walkman (the white bit in the second picture) as a replacement, and the unit works.

My recommendation is steer clear of this mob's products.

[Bloodyaussie]

Cant believe you still have a walkman kicking about.......lol

[mudnut]

Ha ha. Got some parts from old amplifiers that I wrecked decades ago. Hindsight is a wonderful thing. Enthusiasts pay good money for them now.

[Bloodyaussie]

Crazy. .... i chucked stuff like that out 20 years ago..... as a kid i was wired for sound.

[Maxhead]

I'm an electronics engineer by trade but have not touched any circuit level repairs for years. I remember pulling 200 pin circuit mount chips and replacing them . Those days are gone





….................... On the move

[Maxhead]

Ask me what a NOR gate is these day and am farked





….................... On the move

[mudnut]

Same. After countless hours at night school too. These days my eyes are letting me down. My soldering looks like bird turds. I'll have to invest in a huge magnifier/ light and hope I put it away each time I use it, so it doesn't
catch the sun and burn the house down.

[Maxhead]

Same. After countless hours at night school too. These days my eyes are letting me down. My soldering looks like bird turds. I'll have to invest in a huge magnifier/ light and hope I put it away each time I use it, so it doesn't
catch the sun and burn the house down.
One thing I will never forget is soldering and I have to say I;m ferking good at it. I'm wearing glasses these days for those short sight distances

[TPC]

Same. After countless hours at night school too. These days my eyes are letting me down. My soldering looks like bird turds. I'll have to invest in a huge magnifier/ light and hope I put it away each time I use it, so it doesn't
catch the sun and burn the house down.

I am the same, I can still solder good but only with the assistance of a big magnifying light clamped to the workbench. I get younger guys at work to do the fine soldering these days. I used to have excellent eyesight but by the time I was 48 I could no longer do much without glasses.

[threedogs]

Crazy. .... i chucked stuff like that out 20 years ago..... as a kid i was wired for sound.

When a heap of us went over to Kupang my mate brought a Walkman for $380, jaw dropping eh..?

@ TPC I have one of these http://www.ebay.com.au/itm/Double-Third-Hand-Clamp-with-Stand-Alligator-Clips-and-Magnifying-Glass-Shippi-/182012870577?hash=item2a60cfffb1:g:ez0AAOSwVL1V~8P M

[mudnut]

A bit of one-upmanship;

http://www.ebay.com.au/itm/Helping-Hand-Soldering-Stand-LED-Magnifying-Glass-Light-With-3-Lens-Magnifier-/191306338981?hash=item2c8abf12a5:g:gNkAAOSwGvhUFoG i

Although the quality of the lens may be lacking.this sort of unit would solve a few problems.

To solder on to the PCB, I filed the soldering iron to a fine point, but I will invest in a variable heat iron, one day.

[TPC]

When a heap of us went over to Kupang my mate brought a Walkman for $380, jaw dropping eh..?

@ TPC I have one of these http://www.ebay.com.au/itm/Double-Third-Hand-Clamp-with-Stand-Alligator-Clips-and-Magnifying-Glass-Shippi-/182012870577?hash=item2a60cfffb1:g:ez0AAOSwVL1V~8P M


A bit of one-upmanship;

http://www.ebay.com.au/itm/Helping-Hand-Soldering-Stand-LED-Magnifying-Glass-Light-With-3-Lens-Magnifier-/191306338981?hash=item2c8abf12a5:g:gNkAAOSwGvhUFoG i

Although the quality of the lens may be lacking.this sort of unit would solve a few problems.

To solder on to the PCB, I filed the soldering iron to a fine point, but I will invest in a variable heat iron, one day.

We have these on the benches at work, very good when replacing surface mount components or inspecting for cause of faults.

65025

[the evil twin]

Funny how hand skills and soldering technology have evolved...
1960's - hand soldered circuits put men on the moon (according to some)
To get High Reliability Hand Soldering certification meant submitting work pieces for microscopic examination
1980's - multi-layer circuit boards with 5 layers of conductors/printed circuits meant repairs by hand required precision die grinding tools and a low power magnifiers
I remember spending hours or in the odd case days changing components on some avionics gear
2000's - everything is crimped or robot soldered so if the board is screwed throw it away

[threedogs]

Just about a throw away society if you ask me. ppl have lost the ability to repair things
EG old school fitter and turner, these days press some buttons and the job is done. lol Well sorta
How many mechanics [young] would know how to reco a 48mm ida Dellorto carby.
I remember on the auto sewing machines we just plugged each board in to find the faulty one,
then inspect it further for a dry joint somewhere. We were supposed to throw them away.
Received a gold star for finding and fixing them

Panel beaters is another ,,,how many could make a panel
to fit a car from a sheet of flat steel

[Maxhead]

Hey mudnut, do you want these oscilloscope leads?
Have had these sitting here and have no use for them.
BNC type connector .
Let me know your address and they're yours





….................... On the move

[Maxhead]

Oops forgot pic http://www.nissanpatrol.com.au/forums/images/imported/2016/02/220.jpg





….................... On the move

[mudnut]

PM sent, mate.

[GeeYou8]

I remember spending hours or in the odd case days changing components on some avionics gear
Still the same, and they want to pay less per hour than a plumber, sparky or mechanic.
Graham

[TPC]

Funny how hand skills and soldering technology have evolved...
1960's - hand soldered circuits put men on the moon (according to some)
To get High Reliability Hand Soldering certification meant submitting work pieces for microscopic examination
1980's - multi-layer circuit boards with 5 layers of conductors/printed circuits meant repairs by hand required precision die grinding tools and a low power magnifiers
I remember spending hours or in the odd case days changing components on some avionics gear
2000's - everything is crimped or robot soldered so if the board is screwed throw it away

We used to have a shelf where we would put some of the equipment that was considered to expencive to fix and when things got quiet and I felt like a challange I would grab one and spend several hours fixing it. I could fix almost anything given enough time. Most equipment gets sent back yo the factory for board replacement these days.

[mudnut]

We used to have a shelf where we would put some of the equipment that was considered to expencive to fix and when things got quiet and I felt like a challange I would grab one and spend several hours fixing it. I could fix almost anything given enough time. Most equipment gets sent back yo the factory for board replacement these days.

Ha, your post reminded me of my apprenticeship. When the grain haulage season was over, work would become sporadic. To break the monotony, we could go to the electrical room and have a go at repairing 74 volt motors. One day my tradesman decided to challenge me to a race to put a fuel pump motor together.

While we stripped the motors and began assessing them, a small crowd gathered. They were egging us on, and heckling the tradesman. When the tradie got distracted, another bloke swapped out a field winding with a dud one, and an armature with a bent shaft.

The tradie finished his motor only minutes before me, and bagged me out. It was bloody funny when we tested the motors though, because his motor growled and surged crazily.

[GQ TANK]

We used to have a inqustion to replace a main board, when I took over the workshop. I found it was often cheaper in labour and parts to do board changes.

[mudnut]

We used to have a inqustion to replace a main board, when I took over the workshop. I found it was often cheaper in labour and parts to do board changes.

Yeah, the "Golden Wheelbarrow" was rife in a lot of industries, twenty years ago. By the sounds of it repairing anything is just not worth it now.

[Ramsey]

I have a Fluke, forgot what model but it is specifically designed for automotive work and I bought it locally at the Fluke shop. Was'nt cheap but Fluke is very good, some mine sites will only let you on with a Fluke.

[mudnut]

Yeah I have nowhere near a the money for a Fluke though.

[AGman]

Just sold my Fluke on Ebay too...and my scope, soldering iron and everything else...

[mudnut]

How's this for a grab for cash. Jaycar had the QM1577 scopemeter for $399 in last year's catologue, and it is $579 this year.

[AGman]

Get a nice Rigol 100Mhz scope for that money! Check here... (http://www.emona.com.au/specials/oscilloscopes-1/ds1102e.html)

[mudnut]

Yeah I looked at some of their gear. I may have some luck in seeing one of the Hanteck units, as a local bloke is seriously considering buying one.

It would be good to actually see the build quality and features before ordering over the internet for once.

[AGman]

It would be good to actually see the build quality and features before ordering over the internet for once.

Emona are in Melbourne and usually have demo units. There are also places that hire gear if you want to try before you by. I can vouch for Rigol, couldn't fault them.

[mudnut]

I found another basic unit by hantek, https://www.amazon.com/gp/offer-listing/B07K8S2RYZ/ref=dp_olp_new_mbc?ie=UTF8&condition=new

Still battling along with the old crappy allsun. This hantek seems to get good reviews but ...

[mudnut]

The Uni-T 2000 series Benchtop oscilloscope is a bloody marvellous piece of kit. The sig gen I created to run speedos was having interference problems when plugged into 12v. Yet I could only see a nice looking square wave at the 555 timer chip, on the Allosun handheld. I found that having a power lead more than a few centimeters causes the rise on the wave to become fuzzy so I will purchase a small rechargeable 12v battery to install on a new sig gen I am making. I really do recommend the Uni-T as a reasonably priced unit.

[Brissieboy]

The Uni-T 2000 series Benchtop oscilloscope is a bloody marvellous piece of kit. The sig gen I created to run speedos was having interference problems when plugged into 12v. Yet I could only see a nice looking square wave at the 555 timer chip, on the Allosun handheld. I found that having a power lead more than a few centimeters causes the rise on the wave to become fuzzy so I will purchase a small rechargeable 12v battery to install on a new sig gen I am making. I really do recommend the Uni-T as a reasonably priced unit.

Before you bother with the battery idea, try puting a 0.1uF ceramic or vitramon or similar capacitor across the supply rails right at the 555 (pins 1 & 8). And make sure your ground rail is solid and short as possible. Digital circuits need power supply decoupling.

[mudnut]

Before you bother with the battery idea, try puting a 0.1uF ceramic or vitramon or similar capacitor across the supply rails right at the 555 (pins 1 & 8). And make sure your ground rail is solid and short as possible. Digital circuits need power supply decoupling.

I've tried a few ideas as well. Pi filters, common modes chokes, etc. It comes down to the length of the leads. I will try a shielded cable. Also 9v batteries seem to be going flat in no time these days.

[BillsGU]

What ripple frequency was your Pi filter designed to decouple?

[mudnut]

What ripple frequency was your Pi filter designed to decouple?

The 50hz of the power supply I use. I also found placing a small ceramic cap across pins 1 and 8 caused a weird feedback frequency. The best I have so far found is to have a sizable 12 volt gel battery with a an IC7809 to regulate its output. This gives me the option to run a Bd139 as an inverting switch on the 555 output to get a nice AC Square wave. I am now playing with different configurations to get a smooth enough signal at frequencies between 30hz and around440-480hz. I found that around 270hz is 100kph.

[BillsGU]

Have a close look at the ripple frequency. The ripple out of a full wave rectifier is 100hz. The frequency you are trying to generate is close to your filter frequency and you may be getting some feedback via the filters. You could try using an opto coupler to ensure isolation.

Or get one of these: https://www.westlab.com.au/signal-generator-mini-lab-0-1hz-100khz

[mudnut]

Have a close look at the ripple frequency. The ripple out of a full wave rectifier is 100hz. The frequency you are trying to generate is close to your filter frequency and you may be getting some feedback via the filters. You could try using an opto coupler to ensure isolation.

Or get one of these: https://www.westlab.com.au/signal-generator-mini-lab-0-1hz-100khz

I need the sig gen to be portable, small and robust. So I can disconnect the speed sensor connector and test the wiring harness and cluster.
I've been looking into the interference. I think the configuration of the my 555 is too sensitive to outside influence. It uses a capacitor and around 120-130 kohms between pins 1and 2. I will try a different set up using pots between pins 8,7 and 6.

[mudnut]

Yep. The 555 circuit I picked was just to sensitive. I built another one today which handles 10-18 volts, either 240v fed Power supply or 12 battery with no interference whatsoever.

[BillsGU]

Sometimes starting from scratch is the way to go. Beats chasing your tail and trying to fix problems by introducing more problems. Every extra component you put into a circuit is a potential issue.

[mudnut]

Sometimes starting from scratch is the way to go. Beats chasing your tail and trying to fix problems by introducing more problems. Every extra component you put into a circuit is a potential issue.

Too right.

I was looking to buy a dedicated frequency meter kit online to add to the sig gen. Going to use a cheap Jaycar multimeter and strip it down just to display volts and Hz.