Electro-ramblings

Strain gauges are the fundamental sensing elements for many types of sensors, including pressure sensors, load cells, torque sensors, and position sensors. Most strain gauges are foil types, available in a wide choice of shapes and sizes to suit a variety of applications (Figure 1). They consist of a pattern of resistive foil, which is mounted on a backing material.

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I was pondering the failure of my car roof light to operate, wondering if newer cars had gone beyond the corrosion-prone two-pieces-of-metal-and-a-bit-of-plastic door switch.

When reed switches came to mind.

For the uninitiated, these consist of two flat flexible magnetic wires - reeds - held parallel and overlapping in a sealed glass tube.

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Each time, they were in pairs, one on either side of a path in the mountains.

My guess is that they detect the passage of people along the path, possibly by microwave.

But the answer could be much simpler.

Does anyone know for sure what they are, what they do, and how they work?

'Alice'

Respond below, or to alice@electronicsweekly.com

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Several years ago, I used to go to visit Staines in Middlesex (or not in Middlesex - depending on whether you are a Post Office or County Boundary pedant).

Once there, I used to get involved with repairing things and frequently had to buy odds and sods locally.

There were diy sheds in the area, but the local independent diy shop was so good that I seldom even bothered to try the big chain stores.

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For example, the UK is largely stable geologically, and not very steep.

This contrasts with New Zealand which is both steep, and a bit lively on the tectonic front.

Cycling around that fine country a while ago, I got invited in for a coffee by a retired guy who turned out to be: a, very interesting and; b, mostly mad.

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I though it was restricted to photon and sub-atomic stuff, but it appears that a mechanical version is also possible.

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A friend of mine was having a car flat battery problem.

It turned out to be the car radio which, when 'off', drew 186mA.

That's 2W!

Over in the UK, one Cello Electronics has issued the first HDTV that records OTA (Freeview) content directly to an SD card, giving users an easy option for shuffling recorded content to portable players. The set itself boasts twin TV tuners, a built-in EPG, split-screen functionality and an integrated DVD player; as for sizes, you'll find it in 22-, 26- and 32-inch flavours.