Digital Volt meter probs......

[steptoe]

Bought this http://www.ebay.com.au/itm/DIGITAL-AMP- ... 2287571503

after Gannon's suggestion , got it, made a nice little backing plate, glued it into the clock surround, hard wired it into the car using a clip connector to use the clocks power and earth, added the signal wire from diagnostic connector near dizzy to blank connector terminal slot - to read the normal operating 1.7Volts or if knock sensor unit cutting in will read 4.5Volts.

Reads -0.4Volts when running engine @ idle , tap into it with my multimeter, DMM reads the needed. expected 1.69 Volts.

I have checked specs prior to purchase - runs on 12V, reads from 0 to 50V

I am only using Volt read circuit so eliminated two wires. and using instrucions - Run off the meter with separate power supply.
The instructions are in black and white, do not name colours of wires but give diagram showing the shades of grey that colours have and the back plug.

GREEN is to pos 12V separate power supply + at the clock plug
WHITE goes to sep.power supply neg - at the clock plug

next two wires, YELLOW and BLACK involve a current shunt, a load, and a switch - AMPS hook up I gather- remain disconnected.

last wire RED goes to my test wire.

Something is wrong. Have emailed lightning boy 2008

any ideas gents ? and kid

Righto, hooked up the Volt meter sensor wire to a known flattish SLA battery ~ 8.5 Volts - positive to sensor, negative of test battery to car ground , turned Volt meter on - got 6.5V

Next, hooked up a brand new heavy duty alkaline AA battery from Dicka Smith , DMM says it has 1.6Volts, Lightningboys unit -0.04 Volts !

Then the test lead goes to cars battery of 12.something volts unit reads 10.something, give a few revs and she goes up a few volts but not the charging 14V she was showing on the temporary panel meter. I'd suggest the accuracy of this unit is not as specified - more like out by one point two Volts..... at the lower end of the scale

Something to put to lightningboy2008 !

Lifted from the ebay site ....Accuracy: 0.2%±1 word

[fredsub]

Try this: you have that SLA battery, use it to power the meter,
GREEN and WHITE as you say. Then do a voltage measurement using RED and BLACK. Let us know how it reads then8)

the meter needs to be powered by an independent ground source.

[steptoe]

Think I can see where you are coming from Fred. Thanks for the suggestion Good idea....smacks of the problems I had hooking up a trailer LED that shared an earth. A diode in the brake light circuit ? sorted things.

There is two batteries in the diagram, thinking ahead, I am gonna want NOT to need a second battery, maybe just a second earth ??

Out comes the glovebox again ......

It may just be an easy case of using the currently unused black wire as another earth/ground ??

Will report back .....

[pitrack_1]

Jonno,

from the ad:

*Separate DC 6~24V power is required to run off the meter! (If you want to run off the meter with the same source being measured, you need purchase a DC-DC converter together, please contact us before you purchase)

So you need the DC-DC converter. The reason is (I think- need to check, perhaps Gannon?) you need a separate power supply for the voltmeter to reference to. If you try to measure the same power supply against itself, so to speak, you end up with spurious readings related to small currents flowing around in the meter itself.

Think of it a bit like trying to see whether you're heavier than yourself by standing on both sides of the see-saw at once (I'm sure we've all tried this when young... at least the older ones of us allowed to have see-saws before bloody OH&S took the fun out of things!). You end up trying to balance one side against the other with little tilts from slight imbalances in weight on either side. The only way you can compare whether you're heavier or lighter is to have another, separate body on the see-saw.

The DC-DC converter uses some electronic trickery to separate the power source powering the converter from the converter's output power. So you can power the meter from the converter output to measure the battery as it's separated by the converter circuitry.

Or you can look at things like (I am also- cheap and free delivery out of HK/China)
2.2" LCD Digital Panel Voltmeter with Blue Backlight (7.2~20V)
3.8" LCD Digital Clock with In/Outside Thermometer + Voltage Measuring Bar for Vehicles

And if you want a real good multimeter (Fluke) at a cheap price, see
Fluke 17B 2.6" LCD Digital Multimeter Meter (2*AA included). Same model in Oz will probably set you back $200-$300. Fluke's generally regarded as top-shelf stuff, what electricians, scientists, technicians (like me), etc. use as their good 'go-to' unit.

DX/Dealextreme shipping can sometimes take a while (weeks), though.

Hope this helps,

[AshR]

I'll throw 2c in, if you're after a cheap and "works" (not nasty) multimeter "super car shop place" have a yellow one for ~$30 and it comes with a 9v battery.

[steptoe]

Yeah, Patrick , your comments have some relevance to my problem now I look at it, the diagram above the one i used. The first unit you linked does not have specs of reading abilities, I need it to read as low as 1.7 to 4.5V range. Thanks for your efforts

I suppose I tok a shortcut in not asking any Amps reading of it so leaving out a switch and current shunt - should see the thing they included - heavy as lump.

The DC dc converter in diagram gets the power supply wires I used and a few more - need to post diagram up, and supplier my have diagram to use just as Volt reader.

Shame a few lines of trouble shooting not included. I was gonna mod an old Dick DMM but involved jerry rigging and this seemed an affordable option to watch knock management. In here to learn and tinker

Looks bloody great in the place of the clock !

[Gannon]

Yeah pitrack is right, that meter needs a separate power supply, and explained it very well. That is actually different to the panel meter I pointed out to you, the one I suggested had 3 wires, so it shared a common ground.

But for testing if this does work, charge up your sla battery and hide it in the glovebox and use it to power this panel meter, then you will know if it works

[steptoe]

OK , Gannon, you are correct, once again .

http://www.jaycar.com.au/images_uploaded/dcdcconv.pdf

is a little pdf explain on DC-DC converters

If only the unit came with optional wiring diagram for say just Volt metering. Unit has a litle button on front panel, guessing it is to select between metering of Volts and Amps - yet no mention in diagram BUT found mention on ebay item , don't care for Amps hook up unless I have to. And bloody hell the wires are so skrawny .... more for electronics not auto hook-up.

Looks like it is gonna be my bad interpretation ....

[steptoe]

May eithr need my electronic L plates on , or just read more into the dtails of the item I am buying. Got tricked by single source wording.
Have gone back in and bought one of these

http://cgi.ebay.com.au/ws/eBayISAPI.dll ... 0599622187

with the please ask for optional backlighting switch and DC to DC converter or two. The blue digits of the meter above at top are so bright at night, can use it elsewhere, reading fine print and FAQ's of this one from same dude revealed the back light switch option. I have emailed them as requested for option, also put in notes to seller when I paid.

The Volts only meter has FAQ asking if can be used to read single source battery- smart asker - answer is yes and read wiring - not shown on sale page !. Meanwhile , a switchable SLA in the glovebox may have to do

I'm pretty sure all knock sensors have similar output with the diagnostic plug somewhere on later models, reckon others can observe them working....

[steptoe]

nothing but praise for lightningboy2008's customer service, he has replied with colour diagram and adjustments for volts and amps indicated .

Have been running monitoring the knock sensor output voltage - due to my incorrct hook up method, readout changes about depending on electrical changes, lights on etc.

Will be using clock power and earth to switch a relay to allow power on with running only from a 9V tranny battery or 12V SLA in the lovebox , in order to see how it all runs with correct hook up

This first panel is just too bright to consider for in car dash gauge for night driving, glows too bright, gets worse the darker the road gets.

lightningboy got back to me to advise DC to DC converter 1W is ten bucks US, and the optional switch off back light for the new Volts only gauge adds 1.99 US to price.

Gotta love the addresses these ebay sellers use, with room, number, building name, wing this blah, blah not just a business name and address

[steptoe]

The fixs' power supply :



Uploaded with ImageShack.us

an old SLA battery, an old 22A subie relay, some wires, hole in the back of the glovebox so now use the power from the clock connector to trigger the relay which in turn provides SLA battery to power the unit. Now added another earth wire

(yellow from Volts gauge, not the black one -it's for Amps reading)

hooked on up the back of the glovebox and its partner is the 1.6 Volts coming from the test connector under the bonnet on 3 plug ECU'd turbo EA82s only

The old "fill-up-the-clock-space-with-something-useful" trick



Uploaded with ImageShack.us

Need to cover it up at night until my replacement unit arrives SO BRIGHT !! - it'll just be a Volts meter, may or may not need DC-DC converter to isolate battery disturbances that I was getting with this unit, as I did not read the instructions on ebay with enough experience to know what it all meant, so hooked up this battery instead of the DC-DC converter.

Now, back to where I was a year ago, hooking up in an effort to tune this baby a little better - advancing her up from 16 or 18 to maybe 20 with the boost at 10 psi. Had a trailer ~249 kgs and another 100kgs or so on board - got no indication of pinging yesterday.....

Problem sorted - ....NEXT !

[Gannon]

Lookin good Jon.
Shame you cant get an yellow/orange one to match the dashboard.

When I had my EA82T, I once disconnected the knock sensor and went for a drive, it pinged like crazy on 10psi, even with the intercooler. I think running gas may be giving you an advantage

[steptoe]

New one coming is LCD black on grey I think, with the $1.99 optional backlit on/off button. That whole dash section could be filled with little readouts like the Volts from TPS, O2 sensor Volts, but air duct behind.

I am still to test the response of this unit to whacks on the block as have seen with the DMM, ramps Volts up to 4.5 and retards timing 10 degrees, to slowly come back to setting.

Summertime, stinking hot tarmac will be another test, might be time to pull out the water injection espreso pump - run the inverter next to the SLA

add an external cooling fan on the lid .....