The Avometer 8 multimeter has lots of useful ranges, including a special high-resistance range which can measure resistances of up to 20 megohms. This is handy, but it needs a special 15 volt battery. The battery it’s designed for is a BLR121, which was once fairly common but is now dying out. The BLR121 is just about still available but it’s expensive, and since the meter is likely to last a long time I wanted a battery which would also last, and be easy to replace when necessary.
An old solder reel, a bit of copper pipe, and five common-or-garden lithium coin cells is all it took. The coin cells are CR2032, which are 20mm in diameter, and they fit just neatly inside the solder reel. I cut down the reel to form a tube about 35mm long. The stack of five cells is about 16mm long, so I filled the remaining space with a bit of copper pipe cut to about 22mm long. This is what the assembly looked like:
It fitted just neatly into the battery compartment of the meter. The spring contacts are very convenient because you can fit more or less any shape between them!
It works perfectly, and it’s cheap. The CR2032 cells are available for less than 50p each if you shop around, and they have a capacity of around 200mAh. The BLR121 replacements I’ve seen have a capacity of only 40mAh, so the lithium replacement should last about five times longer. Not bad.
Here’s a gratuitous picture of the Avo in use checking the power supply of a BBC Micro.
Nice idea, thank for publishing it – my trusty Avo 8 lives to fight another day 🙂
I’d ditch all my digital meters before I let the Avo go.
A very good idea. Being 30 odd years in the trade I always used my Avo8 for everything! I also trusted it’s accuracy and making a replacement battery! Digital multimeters are nice but I’m still old school! Thanks for the idea!
Really good idea. My Avo 8 Mk2 now tells me the value of a 5.6Meg resistor accurately unlike the digital Fluke8024B which says it is 8.9Meg!
Incidentally 8 coin cells can be bought at Poundland on a card with 4×2032, 2×2025 and 2×2016 (for £1). So £2 buys what you need and the other cells come in handy for other devices.
What a really good idea! I’m going to make one tomorrow.
Oh how absolutely brilliant. My old Avo has been resting in a drawer for far too long, while I have been driven nutty by a digi! Poundland here I come! Thanks enormously.
Many thanks! Brilliant idea, I had to use plastic water pipe with a cut down the side so that the pipe internal diameter could accommodate the cells then fitted the copper pipe extension and hey presto! Now my 53 year old Avo 8 “zeros” easily on the x100 range. Thanks again.
Great! I’m glad it worked for you too.
Thanks for that.
I have not used my AVO for ages but now I see your way forward.