CDT quiescent drain measurement with clamp meter

[clf]

Originally Posted by MSS

I'm afraid that's a bit too high-tech for us Rover drivers - I still use marked-up wooden clothes pegs to identify leads and pipes under the bonnet!

STOP! Buy a camera, it will be cheaper. With the price of timber those wooden clothes pegs are worth a fortune lol

[MSS]

Originally Posted by COLVERT

I used to do that too until the missus gave me hell for getting her washing oily.---

In my household, I can do no wrong!

[polinsteve]

Originally Posted by Mike Noc

I think there is a distinct difference - quiescent current is the expected drain on the battery once all the ECUs have gone up the wooden hill to Bedfordshire, and parasitic drain is any extra current drain due to one or more faults.

Isn't it a lot cheaper and just as effective to just bung a cheap multimeter set to amps in series with the battery to check? If a high reading shows, just pull fuses and/or relays sequentially until the offending circuit is located.

[COLVERT]

Originally Posted by polinsteve

Isn't it a lot cheaper and just as effective to just bung a cheap multimeter set to amps in series with the battery to check? If a high reading shows, just pull fuses and/or relays sequentially until the offending circuit is located.

Could be but don't forget to have a fire extinguisher ready, just in case.----

[Mike Noc]

Originally Posted by polinsteve

Isn't it a lot cheaper and just as effective to just bung a cheap multimeter set to amps in series with the battery to check? If a high reading shows, just pull fuses and/or relays sequentially until the offending circuit is located.

If only it was that simple Steve. Problem is you want to measure the parasitic drain in milliamps but the system can generate a few amps before shutting down and if your cheap meter is in series with the circuit and switched to milliamps then you've blown a fuse at least....and if you wait until everything is shut down and then switch the meter from a higher reading to milliamps you risk waking the ECUs up due to the break in the circuit as you switch over.

Easily got round using a second battery as suggested by French Mike, and I think Harry on here had another way round it.

I agree with you - I just use an inline meter. Not a cheap one though!

[MSS]

To support the above views, you do not need to use a clamp meter. In fact, some of us take pleasure in using inline instruments just for the pleasure of so doing. The clamp meter almost makes it too easy for the diagnostics to be fun!

Steve - the cheap meters do not have fuses in the 10A ports, sometimes even though the silkscreen printing on the instruments states that they do. Usually, the leads are so thin that I would not use them for anything over am amp. There is no substitute for quality in a measuring instrument.

The meter you will receive from myself will only be sent onto you (and the other gents) if it meets basic requirements such as fast blowing fuses and usable test leads. I ordered an extra unit to open up and carry out a thorough inspection as well as test the fuses to blowing point. If the units do not meet what I consider to be basic requirements, they will be sent back. If I send them on, they will be good value usable units.

I have an alternative approach to French Mike's and may put together a dedicated current drain measuring setup using a set of three traditional analogue meters.

[MSS]

Originally Posted by clf

STOP! Buy a camera, it will be cheaper. With the price of timber those wooden clothes pegs are worth a fortune lol

No - wooden pegs are more in keeping with the 75.

Besides, you will be telling me to buy a car with an electronic parking brake next!

[Mike Noc]

Originally Posted by MSS

To support the above views, you do not need to use a clamp meter. In fact, some of us take pleasure in using inline instruments just for the pleasure of so doing. The clamp meter almost makes it too easy for the diagnostics to be fun!

Well this thread is all about clamp meters Maninder, so why not?

If I could justify their use, my garage would be full of all manner of tools and instruments. As it is (although I do own a clamp meter) I love the GhettoTech approach of making do with what is at hand.

[MSS]

Originally Posted by Mike Noc

Well this thread is all about clamp meters Maninder, so why not?

If I could justify their use, my garage would be full of all manner of tools and instruments. As it is (although I do own a clamp meter) I love the GhettoTech approach of making do with what is at hand.

I think we have similar approaches on tools and instruments Mike. An affection for quality but at the same time happy to put together a functional setup using basic gear.

My most extravagant purchase was a Tektronix 465 oscilloscope in the late 1980's. It cost over one month's salary but is a masterpiece of engineering. I still have it and it works perfectly.

Another was a Mitutoyo digital vernier when they first came out. I still have that as well.

[grivas]

Originally Posted by MSS

In another thread a member mentioned the use of a clamp meter for measuring the quiescent current with a clamp meter.

Well, here it is being done earlier today just as a check.

Note the use of a brick to simulate closed bonnet.

https://the75andztclub.co.uk/forum/a...1&d=1632607692

Measurement at time 0 - a few seconds after car being locked with everything switched off

https://the75andztclub.co.uk/forum/a...1&d=1632607830


Measurement at 2 minutes (the drain reaches this value in a number of steps as systems shut down)

https://the75andztclub.co.uk/forum/a...1&d=1632607830


Measurement at 12 minutes

https://the75andztclub.co.uk/forum/a...1&d=1632608005


Measurement at 20 minutes

https://the75andztclub.co.uk/forum/a...1&d=1632608031


The final value is about 25mA.


I would accept up to 50mA but would definitely investigate if the final value was over 75mA


A clamp meter certainly makes taking these measurements rather straightforward. However, the cheap clamp meters are of no use as they only measure AC current. An AC/DC current clamp meter is required and the one being used here is the cheapest decent one of which I am aware. It is available for just over £40 to £50 from various suppliers. It is a UNI-T UT210E.


Some cars have more complex, multi-lead, connections to battery posts e.g. our Vauxhall Twintop. In that case I just use a jump lead to bring out a single lead for the clamp.

Hi, I purchased one of these clamps today, as a result of out conversations, I noticed when I opened the pack there was a ball bearing in the black ripper bag, any idea what it is does it have any use?