Easy battery current measurement - UK Vintage Radio Repair and Restoration Discussion Forum

David G4EBT · 28th Jun 2015, 7:29 pm

Not sure if this has featured before or is widely known, but when wishing to measure the battery current being drawn by equipment powered by 'C' or 'D' cells etc, a 'blade' made from a small piece of double-sided PCB with a lead soldered to each side leads can be pushed between two of the cells and a milliammeter connected to the two flying leads. Simple, but useful! See pic attached.

TonyDuell · 28th Jun 2015, 7:33 pm

It's also (obviously) a way to add an external on/off switch to a battery-powered device, short the wires together to complete the circuit and turn the thing on.

Many years ago I built a sound operated switch kit (I think it was one of those Radio Shack P-box kits, anyone else remember those?) which came with such an attachment so you could use it to turn on a cassette recorder or similar.

Nickthedentist · 28th Jun 2015, 7:50 pm

Cunning David, I'll remember that one!

dseymo1 · 28th Jun 2015, 8:08 pm

As kids, we used a cruder version for switching - bared bell wire taped to each side of a bit of cardboard.
Similarly, I find those test-probe 'tweezers' very useful; I made and used my own before discovering that they were commercially available.

ukcol · 28th Jun 2015, 9:03 pm

Not rocket science, the clever bit is thinking of it in the first place. Well done David.

KeithsTV · 28th Jun 2015, 11:06 pm

That's exactly the method I use at work for measuring current consumption of remote controls. So simple and very effective.

Keith

Tim · 29th Jun 2015, 9:21 am

I'll be using that one in future! Fab idea, and I can see where that would be useful in instance where one cannot use a fuse folder or on/off switch.

Andrew B · 24th Jul 2015, 12:18 pm

Quote:

Originally Posted by KeithsTV

That's exactly the method I use at work for measuring current consumption of remote controls.

For remote controls I am spoiled for choice, I have some IR wireless headphones that receive remotes or I can use the camera on my telephone. Most CMOS cameras are *very* sensitive to IR.

G4XWDJim · 24th Jul 2015, 12:57 pm

Good idea David, I've done the same thing with a piece of cardboard as dseymo1 has suggested.

But I found a problem in that the resistance of the current meter in series with the batteries reduces the voltage applied to the load and the current then taken is lower. How much lower tends to be a bit of a guess depending on the meter used and the range to which it is set. I suppose you could calculate it but I found that connecting a 1 ohm resistor across the two leads and then measuring the volt drop with a digital meter across it had less effect on the working conditions of the circuit.

Jim

ionburn · 24th Jul 2015, 7:40 pm

Believe it or not these pcb devices are commercially available in the form of battery switch adaptors for control of toys by disabled people (usually children). Look up a company called Inclusive Technology. They come complete with 3.5mm inline socket but at £9.00 perhaps few takers outside of their intended market.

28th Jun 2015, 7:29 pm	#1
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,768	Easy battery current measurement Not sure if this has featured before or is widely known, but when wishing to measure the battery current being drawn by equipment powered by 'C' or 'D' cells etc, a 'blade' made from a small piece of double-sided PCB with a lead soldered to each side leads can be pushed between two of the cells and a milliammeter connected to the two flying leads. Simple, but useful! See pic attached. Attached Thumbnails __________________ David. BVWS Member. G-QRP Club member 1339.

28th Jun 2015, 7:33 pm	#2
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,225	Re: Easy battery current measurment It's also (obviously) a way to add an external on/off switch to a battery-powered device, short the wires together to complete the circuit and turn the thing on. Many years ago I built a sound operated switch kit (I think it was one of those Radio Shack P-box kits, anyone else remember those?) which came with such an attachment so you could use it to turn on a cassette recorder or similar.

28th Jun 2015, 7:50 pm	#3
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,866	Re: Easy battery current measurment Cunning David, I'll remember that one!

28th Jun 2015, 8:08 pm	#4
dseymo1 Retired Dormant Member Join Date: Dec 2007 Location: Shropshire, UK. Posts: 3,051	Re: Easy battery current measurment As kids, we used a cruder version for switching - bared bell wire taped to each side of a bit of cardboard. Similarly, I find those test-probe 'tweezers' very useful; I made and used my own before discovering that they were commercially available.

28th Jun 2015, 9:03 pm	#5
ukcol Rest in Peace Join Date: May 2003 Location: Harlaxton, Lincolnshire, UK. Posts: 3,944	Re: Easy battery current measurement Not rocket science, the clever bit is thinking of it in the first place. Well done David.

28th Jun 2015, 11:06 pm	#6
KeithsTV Nonode Join Date: Aug 2007 Location: South Bradford, West Yorkshire, UK. Posts: 2,574	Re: Easy battery current measurement That's exactly the method I use at work for measuring current consumption of remote controls. So simple and very effective. Keith

29th Jun 2015, 9:21 am	#7
Tim Dekatron Join Date: Jan 2003 Location: Bradford on Avon, Wiltshire, UK. Posts: 3,310	Re: Easy battery current measurement I'll be using that one in future! Fab idea, and I can see where that would be useful in instance where one cannot use a fuse folder or on/off switch. __________________ "Nothing is as dangerous as being too modern;one is apt to grow old fashioned quite suddenly."

24th Jul 2015, 12:57 pm	#9
G4XWDJim Octode Join Date: Oct 2008 Location: Littlehampton, West Sussex, UK. Posts: 1,465	Re: Easy battery current measurement Good idea David, I've done the same thing with a piece of cardboard as dseymo1 has suggested. But I found a problem in that the resistance of the current meter in series with the batteries reduces the voltage applied to the load and the current then taken is lower. How much lower tends to be a bit of a guess depending on the meter used and the range to which it is set. I suppose you could calculate it but I found that connecting a 1 ohm resistor across the two leads and then measuring the volt drop with a digital meter across it had less effect on the working conditions of the circuit. Jim

24th Jul 2015, 7:40 pm	#10
ionburn Heptode Join Date: Dec 2014 Location: Lincoln, Lincolnshire, UK. Posts: 583	Re: Easy battery current measurement Believe it or not these pcb devices are commercially available in the form of battery switch adaptors for control of toys by disabled people (usually children). Look up a company called Inclusive Technology. They come complete with 3.5mm inline socket but at £9.00 perhaps few takers outside of their intended market.